WARNING Research and Development

Arthur, A. T., G. M. Cox, N. R. Kuhnert, D. L. Slayter, K. W. Howard, 2005: The National Basin Delineation Project. Bulletin of the American Meteorological Society, 86, 1443-1452.

Brown, R. A., T. A. Niziol, N. R. Donaldson, P. I. Joe, V. T. Wood, 2007: Improved Detection Using Negative Elevation Angles for Mountaintop WSR-88Ds. Part III: Simulations of Shallow Convective Activity Over and Around Lake Ontario. Weather and Forecasting, 22, 839-852.

During the winter, lake-effect snowstorms that form over Lake Ontario represent a significant weather hazard for the populace around the lake. These storms, which typically are only 2 km deep, frequently can produce narrow swaths (20–50 km wide) of heavy snowfall (2–5+ cm/hr) that extend 50–75 km inland over populated areas. Subtle changes in the low-altitude flow direction can make the difference between accumulations that last for 1–2 hr and accumulations that last 24 hr or more at a given location. Therefore, it is vital that radars surrounding the lake are able to detect the presence and strength of these shallow storms.
Starting in 2002, the Canadian operational radars on the northern side of the lake at King City, ON (WKR) and Franktown, ON (XFT) began using elevation angles as low as -0.1 deg and 0.0 deg, respectively, during the winter to more accurately estimate snowfall rates at the surface. Meanwhile, WSR-88D radars in New York State on the southern and eastern sides of the lake—Buffalo (KBUF), Binghamton (KBGM), and Montague (KTYX)—all operate at 0.5 deg and above. KTYX is located on a plateau that overlooks the lake from the east at a height of 0.5 km. With its upward-pointing radar beams, KTYX’s detection of shallow lake-effect snowstorms is limited to the eastern quarter of the lake and surrounding terrain.
The purpose of this paper is to show—through simulations—the dramatic increase in snowstorm coverage that would be possible if KTYX were able to scan downward toward the lake’s surface. Furthermore, if KBUF and KBGM were to scan as low as 0.2 deg, detection of at least the upper portions of lake-effect storms over Lake Ontario and all of the surrounding land area by the five radars would be complete. Over-lake coverage in the lower half (0-1 km) of the typical lake-effect snowstorm would increase from about 40% to about 85%, resulting in better estimates of snowfall rates in landfalling snowbands over a much broader area.

Brown, R. A., V. T. Wood, cited 2007: A Guide for Interpreting Doppler Velocity Patterns: Northern Hemisphere Edition, 2nd ed.. [Available online at ://http://www.nssl.noaa.gov/papers/dopplerguide/.]

Brown, R. A., R. M. Steadham, 2007: Developing site-specific scanning strategies for WSR-88Ds: Important considerations. Preprints, Annual Meeting, Reno, NV, USA, National Weather Association, 94-95.

Brown, R. A., T. A. Niziol, N. R. Donaldson, P. I. Joe, V. T. Wood, 2006: WSR-88D monitoring of shallow lake-effect snowstorms over and around Lake Ontario: Simulations of improvements using lower elevation angles. Preprints, 22nd Conference on Interactive Information Processing Systems, Atlanta, GA, USA, American Meteorological Society, CD-ROM, P2.7. [Available from Rodger A. Brown, National Severe Storms Laboratory, 1313 Halley Circle, Norman, OK, USA, 73069.]

Winner, best poster presentation of conference.

Currently, National Weather Service (NWS) WSR-88D radars do not operate below +0.5 deg. Consequently, shallow lake-effect snowstorms over and around Lake Ontario pose a detection (and warning) challenge for the Buffalo, NY, NWS Forecast Office. Limited measurements in the lower portions of the storms preclude reliable quantitative precipitation estimation (QPE) in much of the coverage area.

This presentation will show how we use simulated scanning strategies to investigate how much detections and QPE would improve using lower elevation angles for the three closest New York State WSR-88Ds: Montague (KTYX), Buffalo (KBUF), and Binghamton (KBGM). Canadian radars at King City and Franktown on the north side of the lake—that operate as low as –0.1 and 0.0 deg, respectively—also are considered.

The Montague radar is located east of Lake Ontario on top of the Tug Hill Plateau 520 m above the lake. Using current scanning strategies, 2-km-deep snowstorms are detectable to a range of only 100 km from the radar (covering the eastern quarter of the lake). The Buffalo radar covers the western half of the lake. Being farther from the lake, the Binghamton radar covers snowstorms that extend southeastward from Lake Ontario.

Simulations show that, when the lowest elevation angle for KTYX is decreased to –0.4 deg, the range of detection of 2-km-deep snowstorms increases from 100 to 220 km. Lowering the lowest elevation angle for KBUF and KBGM to +0.2 deg increases the coverage area (2 km above the surface) by about 60%. Lowering the scanning strategies for these three radars and operating in conjunction with the Canadian radars, shallow lake-effect storms would be detected over the entire lake and surrounding coastal regions and reliable QPE information would be available over nearly the entire region.

Brown, R. A., V. T. Wood, D. C. Dowell, 2006: Interpretation of simulated WSR-88D Doppler velocity signatures of tornadoes associated with nonuniform reflectivities. Preprints, 23rd Conference on Severe Local Storms, St. Louis, MO, USA, Amer. Meteor. Soc., CD-ROM, P9.10.

Typically, when simulated Doppler velocity measurements are made across a tornado, one assumes that the associated reflectivity field is uniform. However, recent measurements made by mobile Doppler radars in the immediate vicinity of tornadoes reveal the presence of a low-reflectivity eye centered on the tornado. The eye arises from the centrifuging of debris and hydrometeors within the tornadic circulation.

Dowell et al. (2005) employed an axisymmetric numerical model to study particle motions and concentrations in tornadoes. We used 1.5-mm-diameter raindrops in the model to produce flow and reflectivity patterns for three different sized tornadoes: medium, large, and very large. The model output then was scanned with a WSR-88D emulator to produce simulated reflectivity and Doppler velocity measurements within the tornadoes.

We found that, except for the rare very large tornado, peak Doppler velocity values associated with a low-reflectivity eye at close range occurred at a smaller radius than in the model tornado. These peak Doppler velocity values also were at a smaller radius than peak values associated with a uniform reflectivity pattern. As distance from the radar increased, the widening radar beam smeared the low-reflectivity eye to produce a more uniform distribution of reflectivity. At the same time, the peak Doppler velocity values approached those obtained for a uniform reflectivity distribution. Thus, in a typical tornado near a WSR-88D, we would expect the presence of a low-reflectivity eye to cause the peak Doppler velocity values to appear at a smaller radius than the radius of the true peak tangential velocities.

Brown, R. A., R. M. Steadham, 2006: Site-specific scanning strategies for WSR-88Ds: Planning for field tests.. Preprints, Annual Meeting, Cleveland, OH, USA, National Weather Association, 46-47.

The lowest elevation angle scanned by all radars in the Weather Surveillance Radar–1988 Doppler (WSR-88D) network is 0.5 deg. Users of Terminal Doppler Weather Radars (TDWRs) and research Doppler radars find that scanning at 0.0 deg reveals the presence of boundaries of forecasting significance that frequently are not evident at 0.5 deg elevation angles. Furthermore, forecasters who prepare warnings based on mountaintop WSR-88D measurements frequently find that the radar overshoots hazardous weather phenomena that threaten the surrounding populace. Simulations indicate that the use of negative elevation angles at mountaintop sites would permit the detection of hazardous weather and would greatly improve the accuracy of surface rainfall and snowfall estimates.
With a basic need for WSR-88Ds to scan at lower elevation angles, the WSR-88D Radar Operations Center—in collaboration with National Weather Service Forecast Offices, National Severe Storms Laboratory, and Federal Aviation Administration—is proposing that each WSR-88D collect data at elevation angles that are best suited for its locale. To test the operational feasibility of lowering elevation angles, a two-year field test is being proposed for six WSR-88Ds, three located on mountaintops and three located on relatively flat terrain. The test plan currently is being evaluated at various administrative levels within the National Weather Service.

Brown, R. A., V. T. Wood, 2005: Interpretation of Doppler velocity patterns. Doppler Radar Theory and Meteorology, Part B, Doppler Radar Meteorological Observations, Federal Meteorological Handbook No. 11 (Revised), NOAA, 6-1-6-20.

Brown, R. A., 2005: Thunderstorms. The Encyclopedia of World Climatology, Springer, 719-724.

Brown, R. A., K. Tarp, 2005: The National Severe Storms Laboratory: 40 Years Young and Going Strong. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, CD-ROM, XXXX.

In 1964, the U.S. Weather Bureau's National Severe Storms Project (NSSP) moved from Kansas City to Norman and changed its name to the National Severe Storms Laboratory (NSSL). For the next 25 years, NSSL continued NSSP's (and its predecessors') long-standing tradition of improving understanding of severe storms by conducting a data collection program each spring that included surface and upper air mesonetworks, research aircraft, and radars. Over the years, Doppler radars (including dual polarization), an instrumented TV transmitter tower, storm intercept teams, and storm electricity measurements were added. In more recent years, spring programs have become more intermittent because of funding constraints, with many associated with national research programs (involving airborne Doppler radars) in the southern Plains. Since the early 1990s, various NSSL sensors have become mobile with the addition of mobile rawinsonde release vehicles, balloon-borne storm electricity sensors, mesonetwork instruments on the tops of cars, and Doppler radars mounted on trucks.

Early NSSL research has had a positive impact on improved public safety. Aircraft studies of turbulence in severe thunderstorms, called Project Rough Rider, during the 1960s, 1970s, and early 1980s led to improved commercial airline safety guidelines in the vicinity of thunderstorms. NSSL Doppler radar studies of thunderstorm mesocyclones and tornadoes during the 1970s led to the decision by the National Weather Service (NWS), U.S. Air Force's Air Weather Service, and Federal Aviation Administration (FAA) to include Doppler capability in their updated operational WSR-88D and Terminal Doppler Weather Radar networks. The WSR-88D has helped forecasters significantly improve severe thunderstorm and tornado warnings, saving countless lives. NSSL continues to support the NWS and FAA by developing and refining radar algorithms for identifying severe weather phenomena and estimating precipitation accumulations, and by helping to design better radar acquisition and processing equipment. A program is currently underway to collect data much faster using a newly-constructed phased array Doppler radar.

By the mid 1980s, NSSL was developing an expertise in numerical modeling. Various techniques, including ensembles, are being investigated to improve the numerical prediction of storm-scale, mesoscale, and synoptic-scale processes. In 1997, soon after the National Severe Storms Forecast Center in Kansas City changed its name to the Storm Prediction Center (SPC), it moved to Norman. With the SPC being collocated with NSSL, there have been many opportunities for NSSL meteorologists to help SPC forecasters develop improved severe storm forecasting techniques, including the application of probabilistic forecasting techniques. Thus, through its various research activities during the past 40 years, NSSL has been instrumental in advancing the state of the art of severe storm detection and prediction.

Brown, R. A., B. A. Flickinger, E. Forren, D. M. Schultz, D. Sirmans, P. L. Spencer, V. T. Wood, C. L. Ziegler, 2005: Improved detection of severe storms using experimental fine-resolution WSR-88D measurements. Weather and Forecasting, 20, 3-14.

Doppler velocity and reflectivity measurements from WSR-88D (Weather Surveillance Radar - 1988 Doppler) radars provide important input to forecasters as they prepare to issue short-term severe storm and tornado warnings. Current-resolution data collected by the radars have an azimuthal spacing of 1.0° and range spacing of 1.0 km for reflectivity and 0.25 km for Doppler velocity and spectrum width. To test the feasibility of improving data resolution, National Severe Storms Laboratory's test-bed WSR-88D (KOUN) collected data in severe thunderstorms using 0.5° azimuthal spacing and 0.25 km range spacing,resulting in eight times the resolution for reflectivity and twice the resolution for Doppler velocity and spectrum width. Displays of current-resolution WSR-88D Doppler velocity and reflectivity signatures in severe storms were compared with displays showing finer-resolution signatures. At all ranges, fine-resolution data provided better depiction of severe storm characteristics. Eighty-five percent of mean rotational velocities derived from fine-resolution mesocyclone signatures were stronger than velocities derived from current-resolution signatures. Likewise, about 85% of Doppler velocity differences across tornado and tornadic vortex signatures were stronger than values derived from current-resolution data. In addition, low-altitude boundaries were more readily detected using fine-resolution reflectivity data. At ranges greater than 100 km, fine-resolution reflectivity displays revealed severe storm signatures, such as bounded weak echo regions and hook echoes, which were not readily apparent on current-resolution displays. Thus, the primary advantage of fine-resolution measurements over current-resolution measurements is the ability to detect stronger reflectivity and Doppler velocity signatures at greater ranges from a WSR-88D.

Brown, R. A., R. M. Steadham, B. A. Flickinger, R. R. Lee, D. Sirmans, V. T. Wood, 2005: New WSR-88D volume coverage pattern 12: Results of field tests. Weather and Forecasting, 20, 385-393.

For the first time since the installation of the national network of WSR-88D radars, a new scanning strategy -- Volume Coverage Pattern 12 -- has been added to the suite of scanning strategies. VCP 12 is a faster version of VCP 11 and has denser vertical sampling at lower elevation angles. This note discusses results of field tests in Oklahoma and Mississippi during 2001 - 2003 that led to the decision to implement VCP 12. Output from meteorological algorithms for a test-bed radar using an experimental VCP were compared with output for a nearby operational WSR-88D using VCP 11 or 21. These comparisons were made for severe storms that were at comparable distances from both radars. Findings indicate that denser vertical sampling at lower elevation angles leads to earlier and longer algorithm identifications of storm cells and mesocyclones, especially those more distant from a radar.

Brown, R. A., J. M. Lewis, 2005: Path to NEXRAD: Doppler radar development at the National Severe Storms Laboratory. Bulletin of the American Meteorological Society, 86, 1459-1470.

In this historical paper, we trace the scientific- and engineering-based steps at the National Severe Storms Laboratory (NSSL) and in the larger weather radar community that led to the development of NSSL's first 10-cm wavelength pulsed Doppler radar. This radar was the prototype for the current NEXRAD (NEXt generation weather RADar) or WSR-88D (Weather Surveillance Radar-1988 Doppler) Network.

We track events, both political and scientific, that led to the establishment of NSSL in 1964. The vision of NSSL's first director, Edwin Kessler, is reconstructed through access to historical documents and oral history. This vision included the development of Doppler radar where research was to be meshed with the operational needs of the U.S. Weather Bureau and its successor the National Weather Service.

Realization of the vision came through steps that were often fitful, where complications arose due to personnel concerns, and where there were always financial concerns. The historical research indicates that: (1) the engineering prowess and mentorship of Roger Lhermitte was at the heart of Doppler radar development at NSSL; (2) key decisions by Kessler in the wake of Lhermitte's sudden departure in 1967 proved crucial to the ultimate success of the project; (3) research results indicated that Doppler velocity signatures of mesocyclones are a precursor of damaging thunderstorms and tornadoes; and (4) results from field testing of the Doppler-derived products during the 1977-1979 Joint Doppler Operational Project -- especially the noticeable increase in the verification of tornado warnings and an associated marked decrease in false alarms -- led to the government decision to establish the NEXRAD network.

Brown, R. A., K. L. Torgerson, 2005: Interpretation of single-Doppler radar signatures in a V-shaped hailstorm: Part II – Evolution of updraft interactions with ambient midaltitude flow. National Weather Digest, 29, 65-80.

Part II of this two-part descriptive study documents characteristics and evolution of the midaltitude flow field arising from interactions of ambient flow with the updraft region of a North Dakota multicell hailstorm. While only single-Doppler radar measurements were available, there were sufficient details in reflectivity and Doppler velocity features to provide interesting deductions about the interactions. The updraft region, located at the upstream end of the storm, typically consisted of two or three actively growing updrafts. Maximum wind speeds occurred along the lateral flanks of the updraft region. The center of the resulting wake region was characterized by a midaltitude channel of low-speed air extending downstream from the middle of the updraft region. Characteristics of the resultant midaltitude vorticity couplet straddling the updraft region did not appear to support the theoretical concept that couplets arise from vertical tilting of low-altitude horizontal vortex tubes. Rather, the vertical momentum of individual updrafts appeared to have collectively presented enough resistance to the approaching midaltitude environmental flow that air slowed down as it flowed through the porous updraft region. As air farther upstream approached the wall of slower-moving air, some of the air was diverted, increasing speed as it flowed around the sides of the updraft region.

Brown, R. A., T. A. Niziol, V. T. Wood, 2005: Improved WSR-88D detection of shallow lake-effect snowstorms over Lake Ontario: Simulations of lowered elevation angles. Preprints, Annual Meeting, St. Louis, MO, USA, National Weather Association, 22-23.

Currently, National Weather Service WSR-88D radars do not operate below +0.5 deg. Consequently, shallow lake-effect snowstorms over and around Lake Ontario pose a detection and warning problem for the Buffalo NWS Forecast Office. We use simulated scanning strategies to investigate how much detections would increase using lower elevation angles for the three closest New York State WSR-88Ds: Montague (KTYX), Buffalo (KBUF), and Binghamton (KBGM). Two Canadian radars on the north side of the lake—that operate as low as 0.0 deg—also are considered.

The Montague radar is located east of Lake Ontario on top of the Tug Hill Plateau 520 m above the lake. Using the current scanning strategies, 2-km-deep snowstorms are detectable to a range of only 100 km from the radar (covering the eastern quarter of the lake). The Buffalo radar covers the western half of the lake. Being farther from the lake, the Binghamton radar covers snowstorms over the southern lake shore.

Simulations show that, when the lowest elevation angle for KTYX is decreased to –0.3 deg, the range of detection of shallow snowstorms increases by 100 km. Lowering the lowest elevation angle for KBUF and KBGM to +0.3 deg increases the coverage range by 20 km. By lowering the scanning strategies for these three radars and operating in conjunction with the Canadian radars, lake-effect storms would be detected over the entire lake and surrounding coastal regions.

Burgess, D. W., T. D. Crum (other)R. J. Vogt, 2008: Impact of wind farms on WSR-88D radars. Extended Abstracts, 24rd Conference on Interactive Information Processing Systems (IIPS), New Orleans, LA, USA, AMS, CD-ROM, bB.3.

Burgess, D. W., T. Crum, R. J. Vogt, 2007: Impacts of wind turbine farms on WSR-88D radars. Preprints, 33rd Int. Conf. on Radar Meteor., 6-10 August, 2007, Cairns, Australia, AMS, CD-ROM, 13B.6.

Burgess, D. W., D. C. Dowell, L. J. Wicker, A. Witt, 2005: Detailed comparison of observed and modeled tornadogenesis. Preprints, 32nd Conf. on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, 10R.4.

Davies-Jones, R. P., 2006: Integrals of the vorticity equation. Part I: General three- and two-dimensional flows.. Journal of the Atmospheric Sciences, 63, 598-610.

The integral of the vector vorticity equation for the vorticity of a moving parcel in 3D baroclinic flow with friction is cast in a new form. This integral of the vorticity equation applies to synoptic-scale or mesoscale flows and to deep compressible or shallow Boussinesq motions of perfectly clear or universally saturated air. The present integral is equivalent to that of Epifanio and Durran in the Boussinesq limit, but its simpler form reduces easily to Dutton’s integral when the flow is assumed to be isentropic and frictionless.
The integral for vorticity has the following physical interpretation. The vorticity of a parcel is composed of barotropic vorticity, baroclinic vorticity, which originates from solenoidal generation, and vorticity stemming from frictional generation. Its barotropic vorticity is the result of freezing into the fluid the w field (specific volume times vorticity) that is present at the initial time. Its baroclinic vorticity is the vector sum of contributions from small subintervals of time that partition the interval between initial and current times. In each subinterval, the baroclinic torque generates a small vector element of vorticity and hence w. The contribution to the current baroclinic vorticity is the result of freezing this element of w into the fluid immediately after its formation. The physical interpretation of vorticity owing to frictional generation is identical except the torque is frictional rather than solenoidal.
The baroclinic vorticity is decomposed into a part that would occur if the current entropy of the flow were conserved materially backward in time to the initial time and an adjustment term that accounts for production of entropy gradients in material coordinates during this interval. A method for computing all the vorticity parts in an Eulerian framework within a 3D numerical model is outlined.
The usefulness of the 3D vorticity integral is demonstrated further by deriving Eckart’s, Bjerknes’ and Kelvin’s circulation theorems from it in relatively few steps, and by showing that the associated expression for potental vorticity is an integral of the potential-vorticity equation and implies conservation of potential vorticity for isentropic frictionless motion of clear air (Ertel’s theorem). Lastly, a formula for the helicity density of a parcel is obtained from the vorticity integral and an expression for the parcel’s velocity, and verified by proving that it is an integral of the equation for helicity density.

Davies-Jones, R. P., 2006: Integrals of the vorticity equation. Part II: Special two-dimensional flows.. Journal of the Atmospheric Sciences, 63, 611-616.

In Part I, a general integral of the 2D vorticity equation was obtained. This is a formal solution for the vorticity of a moving tube of air in a 2D unsteady stratified shear flow with friction. This formula is specialized here to various types of 2D flow. For steady inviscid flow, the integral reduces to an integral found by Moncrieff and Green if the flow is Boussinesq and to one obtained by Lilly if the flow is isentropic. For steady isentropic frictionless motion of clear air, several quantities that are invariant along streamlines are found. These invariants provide another way to obtain Lilly’s integral from the general integral.

Davies-Jones, R. P., 2006: Tornadogenesis in supercell storms – what we know and what we don’t know. Preprints, Symposium on the Challenges of Severe Convective Storms,, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, 2.2.

invited paper

Davies-Jones, R. P., V. T. Wood, 2006: Simulated Doppler velocity signatures of evolving tornado-like vortices. Journal of Atmospheric and Oceanic Technology, 23, 1029-1048.

Exact solutions of the Navier-Stokes or Euler equations of motion and the continuity equation in cylindrical coordinates for 3D, axisymmetric, inviscid or laminar flows are utilized to represent evolving vortices that roughly model tornado cyclones or misocyclones contracting to tornadoes. These solutions are unsteady versions of the diffusive Burgers-Rott vortex and the inviscid Rankine combined vortex. They satisfy the free-slip condition at the ground. Different vortices are obtained by choosing different values of the constant eddy viscosity and uniform horizontal convergence while holding the circulation at infinity constant. A simulated WSR-88D radar is employed to generate time-varying Doppler velocity signatures in uniform reflectivity of these analytical vortices at ranges of 25 and 50 km from the radar. Mean Doppler velocities are determined by computing 3D integrals over effective resolution volumes. Magnitudes of Doppler vortex signatures at different times in the evolution of the stationary vortices are computed for effective beamwidths of 1.02º and 1.39º, which correspond to azimuthal sampling intervals of 0.5º and 1.0º, respectively. Four tornado predictors, rotational velocity, shear, excess rotational kinetic energy, and circulation, are examined.
Results of the simulations show that for smaller effective beamwidths, Doppler vortex signatures are stronger and exceed fixed threshold values of rotational velocity and shear earlier. With finer azimuthal resolution, tornado-cyclone, misocyclone, or tornado signatures switch to tornadic vortex signatures later. Circulations of the vortex signatures give good estimates of the circulations of the simulated tornadoes and tornado cyclones with relative insensitivity to range, effective beamwidth, and stage of evolution High circulation and convergence values of a rotation signature reveal the potential for a tornado earlier than all the other predictors, which increase significantly during tornadogenesis.

Davies-Jones, R. P., 2006: Global properties of a simple axisymmetric simulation of tornadogenesis. Preprints, 23rd Conference on Severe Local Storms, St Louis, MO, USA, American Meteorological Society, P10.2.

Davies-Jones, R. P., V. T. Wood, 2005: Simulated Doppler velocity signatures of evolving tornado-like vortices.. Preprints, 32nd Conf. on Radar Meteorology,, Albuquerque, NM, USA, Amer. Meteor. Soc., CD-ROM, P15R.8.

Dowell, D. C., C. R. Alexander, J. M. Wurman, L. J. Wicker, 2005: Centrifuging of hydrometeors and debris in tornadoes: Radar-reflectivity patterns and wind-measurement errors. Monthly Weather Review, 133, 1501-1524.

High-resolution Doppler radar observations of tornadoes reveal a distinctive tornado-scale signature with the following properties: a reflectivity minimum aloft inside the tornado core (described previously as an "eye"), a high-reflectivity tube aloft that is slightly wider than the tornado core, and a tapering of this high-reflectivity tube near the ground. The results of simple one-dimensional and two-dimensional models demonstrate how these characteristics develop. Important processes in the models include centrifugal ejection of hydrometeors and/or debris by the rotating flow and recycling of some objects by the near-surface inflow and updraft.

Doppler radars sample the motion of objects within the tornado rather than the actual airflow. Since objects move at different speeds and along different trajectories than the air, error is introduced into kinematic analyses of tornadoes based on radar observations. In a steady, axisymmetric tornado, objects move outward relative to the air and move more slowly than the air in the tangential direction; in addition, the vertical air-relative speed of an object is less than it is in still air. The differences between air motion and object motion are greater for objects with greater characteristic fall speeds (i.e., larger, denser objects) and can have magnitudes of tens of meters per second. Estimates of these differences for specified object and tornado characteristics can be obtained from an approximation of the one-dimensional model.

Doppler On Wheels observations of the 30 May 1998 Spencer, South Dakota, tornado demonstrate how the apparent tornado structure can change when the radar-scatterer type changes. When the Spencer tornado entered the town and started lofting debris, changes occurred in the Doppler velocity and reflectivity fields that are consistent with an increase in mean scatterer size.

Elmore, K. L., K. A. Scharfenberg, C. Legett, 2007: The NSSL winter hydrometeor classification ground truth program: Public involvement in science. Preprints, 31st Intl. Conf. on Radar Meteor., Cairns, Australia, Amer. Meteor. Soc., CD-ROM, P10.9.

During the winter of 2006-2007, a concerted effort was made by the National Severe Storms Laboratory to collect polarimetric radar data using the KOUN radar during winter precipitation events. Simultaneously, observations of precipitation type within a radius of 150 km of KOUN were solicited from the public. Public response has resulted in about 2500 individual observations of winter precipitation type over the course of three major events. These data are intended to be used to both verify the current hydrometeor classification algorithm performance in winter weather events, and to enhance the algorithm's performance. This paper discusses the nature of the ground truth data collected, its overall utility, the nature and scope of quality assurance checking, how event timing affects observation availability, how best to solicit and encourage public participation, and examples of how the data are being used.

Elmore, K. L., M. E. Baldwin, D. M. Schultz, 2006: Field Significance Revisited: Spatial Bias Errors in Forecasts as Applied to the Eta Model. Monthly Weather Review, 134, 519-531.

The spatial structure of bias errors in numerical model output is valuable to both model developers and operational forecasters, especially if the field containing the structure itself has statistical significance in the face of naturally occurring spatial correlation. A semi-parametric
Monte Carlo method, along with a moving blocks bootstrap method is used to determine the field significance of spatial bias errors within spatially correlated error fields. This process can be completely automated, making it an attractive addition to the verification tools already in use. The process demonstrated here results in statistically significant spatial bias error fields at any arbitrary
significance level.

To demonstrate the technique, 0000 and 1200 UTC runs of the operational Eta model and the operational Eta model using the Kain–Fritsch convective parameterization scheme are examined. The resulting fields for forecast errors for geopotential heights and winds at 850, 700, 500, and 250 hPa over a period of 14 months (26 January 2001 through 31 March 2002) are examined and compared using the verifying initial analysis. Specific examples are shown, and some plausible causes for the resulting significant bias errors are proposed.

Elmore, K. L., D. M. Schultz, M. E. Baldwin, 2006: The Behavior of Synoptic-Scale Errors in the Eta Model. Monthly Weather Review, 134, 3355-3366.

A previous study of the mean spatial bias errors associated with operational forecast models motivated an examination of the mechanisms responsible for these biases. One hypothesis for the cause of these errors is that mobile synoptic-scale phenomena are partially responsible. This paper explores this hypothesis using 24-h forecasts from the operational Eta model and an experimental version called the EtaKF.
For a sample of 44 well-defined upper-level short-wave troughs arriving on the west coast of the United States, 70% were underforecast (as measured by the 500-hPa geopotential height), a likely result of being undersampled by the observational network. For a different sample of 45 troughs that could be tracked easily across the country, consecutive model runs showed that the height errors associated with 44% of the troughs generally decreased in time, 11% increased in time, 18% had relatively steady errors, 2% were uninitialized entering the west coast, and 24% exhibited some other kind of behavior. Thus, landfalling short-wave troughs were typically underforecast (positive errors, heights too high), but these errors tended to decrease as they moved across the United States, likely a result of being better initialized as the troughs became influenced by more upper-air data. Nevertheless, some errors in short-wave troughs were not corrected as they fell under the influence of supposedly increased data amount and quality. These results indirectly show the effect that the amount and quality of observational data has on the synoptic-scale errors in the models. On the other hand, long-wave ridges tended to be underforecast (negative errors, heights too low) over a much larger horizontal extent.
These results are confirmed in a more systematic manner over the entire dataset by segregating the model output at each grid point by the sign of the 500-hPa relative vorticity. Although errors at grid points with positive relative vorticity are small but positive in the western United States, the errors become large and negative farther east. Errors at grid points with negative relative vorticity, on the other hand, are generally negative across the United States. A large negative bias observed in the Eta and EtaKF over the southeast United States is believed to be due to an error in the longwave radiation scheme interacting with water vapor and clouds. This study shows that model errors may be related to the synoptic-scale flow, and even large scale features such as long-wave troughs can be associated with significant large-scale height errors.

Available online at ://http://ams.allenpress.com/.

Elmore, K., 2005: Alternatives to the Chi-Square test for evaluating rank histograms from ensemble forecasts. Weather and Forecasting, 20, 789-795.

Fang, M., J. Zhang, J. K. Williams, J. A. Craig, 2008: Three-Dimensional Mosaic of the Eddy Dissipation Rate Fields from WSR-88Ds. Extended Abstracts, The 88th AMS annual conference, New Orleans, LA, USA, AMS, P4.5. [Available from Ming Fang, 408C, Wadsack Dr., Norman, OK, USA, 73072.]

A national 3-D mosaic of Eddy Dissipation Rate (EDR) is being developed, prototyped, and evaluated through collaboration between the National Center for Atmospheric Research (NCAR) and NOAA’s National Severe Storms Lab (NSSL) under the auspices of the FAA Aviation Weather Research Program’s Turbulence and Advanced Weather Radar Techniques (AWRT) Research Teams. The EDR field is an indicator of in-cloud turbulence intensity derived from individual WSR-88Ds’ spectrum width data by the NEXRAD Turbulence Detection Algorithm (NTDA), which was developed at NCAR by the Turbulence Research Team. The NTDA software has been delivered to the National Weather Service and will be implemented operationally on all WSR-88Ds beginning in the spring of 2008, providing EDR and associated confidence data as a polar-grid Level III field. A national 3-D mosaic of the EDR field will provide a high-resolution, rapid update, in-cloud turbulence product for use in aviation safety decision support products. In particular, the Turbulence Research Team plans to incorporate it into a new rapid-update version of the Graphical Turbulence Guidance product, which will directly address convective turbulence for the first time.

The EDR mosaic has been developed using NTDA data from 20 radars covering the Chicago to Washington DC region that are being generated at NCAR and transferred to NSSL in real-time. A mosaic scheme previously developed by the AWRT Research Team for creating 3-D reflectivity mosaics was used as a starting point, but differences between EDR and reflectivity has required a number of adjustments; in addition, the 3-D mosaic scheme was modified to utilize the confidence values produced by the NTDA. The prototype regional 3-D in-cloud turbulence mosaic was evaluated based on comparisons with EDR values obtained from an automated measurement and reporting system on United Airlines aircraft. Continuing evaluation and tuning efforts are expected to lead to enhancements in the current mosaic scheme and establishment of a methodology that will eventually be used in the operational national 3-D in-cloud turbulence mosaic.

Fang, M., R. J. Doviak, P. Zhang, 2008: An Analytical Expression For Doppler Spectra Related to TerminalVelocity With Non-uniform Drop Size Distribution. Extended Abstracts, The 88th AMS annual meeting, New Orleans, LA, USA, AMS, P2.27. [Available from Ming Fang, 408C, Wadsack Dr., Norman, OK, USA, 73072.]

Starting from the correlation function and neglecting other spectrum broadening mechanisms, an analytical expression for the Doppler spectrum is related to the drop’s terminal velocity and size distribution if there is a unique relationship between drop’s diameter and its terminal velocity. The derivation does not require drop size distribution to be homogeneous. This generalized expression reduces to previously derived expression if drop size distribution is uniform.

Fang, M., R. J. Doviak, 2008: WSR-88D Observed Spatial Spectra of Turbulence in Precipitation. Extended Abstracts, The 88th AMS annual meeting, New Orleans, LA, USA, AMS, 12.6. [Available from Ming Fang, 408C, Wadsack Dr., Norman, OK, USA, 73072.]

Different algorithms are designed to isolate the turbulent component from radar measured Doppler velocity. Spatial spectra along the quasi-horizontal direction are then obtained in stratiform rain, storms and squall lines. The slope of horizontal spectra in stratiform rain and storms is close to -5/3 on a log-log graph up to at least scales of 10 km and 7 km respectively. The spectrum in a squall line has a steeper slope than -5/3 up to scales at least 17 km. The scales at low wave number end on the spectra are so large that the spectra could not be due to three-dimensional isotropic turbulence but to two-dimensional turbulence.

Fang, M., R. J. Doviak, 2005: Corrections to and considerations of the spectrum width equation. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, P4R.2.

Gourley, J. J., P. Tabary, J. Parent-du-Chatelet, 2007: Empirical estimation of attenuation from differential propagation phase measurements at C-band. Journal of Applied Meteorology and Climatology, 46, 306-317.

Gourley, J. J., P. Tabary, J. Parent-du-Chatelet, 2007: A fuzzy logic algorithm for the separation of precipitating from non-precipitating echoes using polarimetric radar observations. Journal of Atmospheric and Oceanic Technology, 24, 1439-1451.

Gourley, J. J., P. Tabary, J. Parent-du-Chatelet, 2006: Data quality of the Meteo-France C-band polarimetric radar. Journal of Atmospheric and Oceanic Technology, 23, 1340-1356.

Gourley, J. J., B. E. Vieux, 2006: A method for identifying sources of model uncertainty in rainfall-runoff simulations.. Journal of Hydrology, 327, 68-80.

Gourley, J. J., B. E. Vieux, 2005: A Method for Evaluating the Accuracy of Quantitative Precipitation Estimates from a Hydrologic Modeling Perspective. Journal of Hydrometeorology, 6, 115-133.

Hane, C. E., D. L. Andra Jr., K. Trammell, F. H. Carr, 2005: Development of a tool to aid in forecasting the evolution of Great Plains MCSs during late morning hours. AIRMASS 2005 Conference, Wichita, KS, USA, American Meteorological Society, CD-ROM, XXXX.

Hane, C. E., D. L. Andra, Jr., J. A. Haynes, T. E. Thompson, F. H. Carr, 2005: On the Importance of Environmental Factors in Influencing the Evolution of Morning Great Plains MCS Activity during the Warm Season. Extended Abstracts, Eleventh Conference on Mesoscale Processes, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, P3M.6.

Jorgensen, D. P., R. M. Rauber, K. F. Heideman, M. E. Fernau, M. A. Friedman, A. L. Schein, 2007: JOURNALS AND MONOGRAPHS: The evolving publication process of the AMS. The history of scholarly publications of the AMS. Bulletin of the American Meteorological Society, 88, 1122-1126.

Jorgensen, D. P., R. M. Rauber, K. F. Heideman, M. E. Fernau, M. A. Friedman, A. L. Schein, 2007: JOURNALS AND MONOGRAPHS: The evolving publication process of the AMS. What's new? The electronic workflow. Bulletin of the American Meteorological Society, 88, 1131-1134.

Jorgensen, D. P., R. M. Rauber, K. F. Heideman, M. E. Fernau, M. A. Friedman, A. L. Schein, 2007: JOURNALS AND MONOGRAPHS: The evolving publication process of the AMS. What determines how much we pay? The cost of AMS publications. Bulletin of the American Meteorological Society, 88, 1129-1131.

Jorgensen, D. P., R. M. Rauber, K. F. Heideman, M. E. Fernau, M. A. Friedman, A. L. Schein, 2007: JOURNALS AND MONOGRAPHS: The evolving publication process of the AMS. What happens to my paper after it is sent to the AMS? Peer review and publication. Bulletin of the American Meteorological Society, 88, 1126-1129.

Kuhlman, K., D. MacGorman, D. Rust, P. Krehbiel, B. Rison, 2007: Lightning in the anvil region of a supercell storm. Preprints, 13th International Conference on Atmospheric Electricity, Beijing, China, IUGG/Commission on Atmospheric Electricity, PS5-8.

The Thunderstorm Electrification and Lightning Experiment (TELEX) took place in central Oklahoma during the 2003 and 2004 convective seasons to study the lightning, dynamics and microphysics of thunderstorms. One storm from this field project, a high-precipitation tornadic supercell occurred on 29 May 2004. In this storm, the Oklahoma Lightning Mapping Array detected lightning extending over one hundred kilometers away from the core of the supercell. Lightning is known to occur in the anvil region of supercells; typically this lightning is initiated in the core of the storm and extends out through the anvil. In the 29 May 2004 storm, however, some flashes actually initiated in the anvil region and the subsequent leaders progressed back towards the core of the storm. Some of these flashes were negative cloud-to-ground flashes that initiated over 50 km away from the core and struck ground beneath the anvil close to the initiation point. It appears that interaction between the anvil of this supercell and an anvil of opposite polarity from a weaker left-moving cell to the north was responsible for initiating this lightning.

Kuhlman, K. M., C. L. Ziegler, E. R. Mansell, D. R. MacGorman, J. M. Straka, 2006: Numerically Simulated Electrification and Lightning of the 29 June 2000 STEPS Supercell Storm. Monthly Weather Review, 134, 2734-2757.

A three-dimensional dynamic cloud model incorporating airflow dynamics, microphysics, and thunderstorm electrification mechanisms is used to simulate the first 3 h of the 29 June 2000 supercell from the Severe Thunderstorm Electrification and Precipitation Study (STEPS). The 29 June storm produced large flash rates, predominately positive cloud-to-ground lightning, large hail, and an F1 tornado. Four different simulations of the storm are made, each one using a different noninductive (NI) charging parameterization. The charge structure, and thus lightning polarity, of the simulated storm is sensitive to the treatment of cloud water dependence in the different NI charging schemes. The results from the simulations are compared with observations from STEPS, including balloon-borne electric field meter soundings and flash locations from the Lightning Mapping Array. For two of the parameterizations, the observed “inverted” tripolar charge structure is well approximated by the model. The polarity of the ground flashes is opposite that of the lowest charge region of the inverted tripole in both the observed storm and the simulations. Total flash rate is well correlated with graupel volume, updraft volume, and updraft mass flux. However, there is little correlation between total flash rate and maximum updraft speed. Based on the correlations found in both the observed and simulated storm, the total flash rate appears to be most representative of overall storm intensity.

Available online at ://http://www.ametsoc.org.

Langston, C., J. Zhang, K. Howard, 2007: Four-Dimensional Dynamic Radar Mosaic. Journal of Atmospheric and Oceanic Technology, 24, 776-790.

MacGorman, D. R., T. Filiaggi, R. L. Holle, R. A. Brown, 2007: Negative Cloud-to-Ground Lightning Flash Rates Relative to VIL, Maximum Reflectivity, Cell Height, and Cell Isolation. Journal of Lightning Research, 1, 132-147.

This study relates storm cell parameters derived automatically from the Doppler radars of the United States National Weather Service to negative cloud-to-ground lightning activity detected by the United States National Lightning Detection Network. Data from the central United States were processed for over 1200 cells from seventeen days. Each cell’s maximum ground flash rate was compared to a subjective rating of the degree of cell isolation and to three radar-derived cell parameters: maximum reflectivity, maximum vertically integrated liquid (VIL), and the maximum vertical thickness having at least 30 dBZ reflectivity above the 0 deg C isotherm (similar to 30-dBZ cell height). Of the three parameters, the maximum 30-dBZ thickness of cells had the most useful relationship: The mean and modal values of ground flash rates increased with increasing 30-dBZ thickness, and the mean and modal values of 30-dBZ thickness increased with increasing flash rates. However, large ground flash rates provided a better diagnostic for large 30-dBZ thickness than large 30-dBZ thickness provided for large ground flash rates. The degree of cell isolation and the complexity of cell evolution also had a large effect: Cells which were less isolated or whose evolution was more complex were more likely to produce a ground flash and larger ground flash rates. Besides effects of storm complexity and size suggested by previous investigators, we suggest that the more complex charge distribution produced by having older cells nearby improves a cell’s probability of access to the lower positive charge typically needed to initiate negative ground flashes.

MacGorman, D., K. Kuhlman, D. Rust, M. Biggerstaff, T. Schuur, J. Straka, P. Krehbiel, B. Rison, L. Carey, 2007: Lightning and electrical structure of a heavy-precipitation supercell storm during TELEX. Preprints, 13th International Conference on Atmospheric Electricity, Beijing, China, IUGG/Commission on Atmospheric Electricity, OS5-1.

The Thunderstorm Electrification and Lightning Experiment (TELEX) observed a heavy-precipitation (HP) supercell storm in central Oklahoma on 29 May 2004. In a HP supercell storm, the initial location of the mesocyclone, which is the parent rotation of tornadoes, is embedded well within the precipitation of the storm, instead of being on the edge of the storm (as in classic and low-precipitation supercell storms). Two 5-cm wavelength mobile Doppler radars were positioned near the storm and collected volume scans every 3 minutes for 3 h beginning as the storm became supercellular. The storm had supercell characteristics for this entire period. The Oklahoma Lightning Mapping Array provided three-dimensional data throughout the storm’s supercellular stage and provided two-dimensional data from the time of storm initiation in western Oklahoma. A 10-cm wavelength polarimetric radar also provided data for much of this period.
Lightning flash rates became extraordinarily large as the storm evolved into a supercell and its motion turned rightward. Flash rates increased again (to an estimated peak value of almost 500 flashes per minute) shortly before the storm produced a tornado rated F2 on the Fujita scale. During this period, an upward pulse in lightning density extended as high as 18 km MSL in a plume extending above the equilibrium level, and the region of lightning activity pulsed eastward far into the anvil, up to 150 km from the western edge of the storm. A series of minimums in the plan projection of lightning density (i.e., lightning holes) formed just above the bounded weak echo region. A dual-Doppler synthesis of wind during one volume scan shows the lightning hole was co-located with large vertical wind speeds in the rotating updraft. The hole apparently occurred because precipitation particles had little time to grow and gain charge in the strong updraft before they were lifted to upper regions of the storm and advected outward by flow from the diverging updraft. Cloud-to-ground lightning activity in and near heavy precipitation was dominated initially by negative ground flashes, but during part of the supercell phase, evolved to become dominated by positive ground flashes. Lightning mapping data suggest that, when positive ground flashes dominated, the vertical polarity of the storm’s electrical structure was inverted from the usual polarity.

MacGorman, D., I. Apostolakopoulos, A. Nierow, J. Cramer, N. Demetriades, P. Krehbiel, 2006: Improved Timeliness of Thunderstorm Detection from Mapping a Larger Fraction of Lightning Flashes. Preprints, 1st International Lightning Meteorology Conference, Tucson, AZ, USA, Vaisala, CD-ROM, N/A. [Available from Vaisala, Inc., Tucson Operations, 2705 E. Medina Rd., Tucson, AZ, USA, 85706.]

One application of lightning ground strike mapping systems has been thunderstorm detection. However, the climatological ratio of in-cloud flashes to cloud-to-ground flashes typically is greater than 2:1. Thus, systems that map either cloud flashes or all types of flashes will detect storms more quickly and reliably. The improvement typically is even greater than would be expected simply from the greater number of samples, because the first flashes produced by a storm usually are cloud flashes. However, the improvement obviously is affected by the fraction of flashes that a lightning mapping system detects. Because it costs substantially more to detect a larger fraction of all flashes, one would like to know how much lead time will be added by various levels of lightning detection. The U.S. National Lightning Detection Network (NLDN) being used by the National Weather Service is now capable of detecting roughly 10-20% of cloud flashes, in addition to a much larger fraction of cloud-to-ground flashes, over the contiguous United States. So far, this cloud flash option has been turned on only in a test region. The optical lightning mapper being planned for GOES-R is expected to detect 80-90% of cloud flashes. Some research mapping systems can detect essentially all but the smallest flashes throughout their coverage region. We analyzed the test cloud flash data from the NLDN network to see how much that system’s cloud flash detection would improve thunderstorm detection. Furthermore, we analyzed data from VHF lightning mapping systems that detect almost all flashes, to evaluate how much the timeliness of thunderstorm detection can be improved over what is now achieved with ground strike mapping systems. In north Texas and Oklahoma, 50% of thunderstorms produced a cloud-to-ground flash within 5-10 minutes of their first cloud flash, but in roughly 10% of storms, no cloud-to-ground flash occurred within an hour of the first cloud flash. Behavior was much different in storms over the High Plains of northwest Kansas and northeast Colorado. There it required 30 minutes after the first cloud flash for 50% of storms to produce a cloud-to-ground flash, and 20% of storms produced no cloud-to-ground flash within their first hour of lightning activity. One might expect such a result on the basis of climatological studies showing that cloud flashes comprise at least 90% of all lightning over much of the High Plains and in a few other regions of the country.

MacGorman, D. R., W. D. Rust, P. Krehbiel, W. Rison, E. Bruning, K. Wiens, 2005: The electrical structure of two supercell storms during STEPS. Monthly Weather Review, 133, 2583-2607.

Balloon soundings were made through two supercell storms during the Severe Thunderstorm Electrification and Precipitation Study (STEPS) in summer 2000. Instruments measured the vector electric field, temperature, pressure, relative humidity, and balloon location. For the first time, soundings penetrated both the strong updraft and the rainy downdraft region of the same supercell storm. In both storms, the strong updraft had fewer vertically separated charge regions than found near the rainy downdraft, and the updraft's lowest charge was elevated higher, its bottom being near the 40-dBZ boundary of the weak-echo vault. The simpler, elevated charge structure is consistent with the noninductive graupel-ice mechanism dominating charge generation in updrafts. In the weak-echo vault, the amount of frozen precipitation and the time for particle interactions are too small for significant charging. Inductive charging mechanisms and lightning may contribute to the additional charge regions found at lower altitudes outside the updraft. Lightning mapping showed that the in-cloud channels of a positive ground flash could be in any one of the three vertically separated positive charge regions found outside the updraft, but were in the middle region, at 6-8 km MSL, for most positive ground flashes. Our data are consistent with the electrical structure of these storms having been inverted in polarity from that of most storms elsewhere. We hypothesize that the observed inverted-polarity cloud flashes and positive ground flashes were caused by inverted-polarity storm structure, possibly due to a larger than usual rime accretion rate for graupel in a strong updraft.

MacGorman, D., D. Rust, T. Schuur, M. Biggerstaff, J. Straka, C. Ziegler, E. Mansell, P. Krehbiel, W. Rison, T. Hamlin, L. Carey, E. Bruning, K. Kuhlman, N. Ramig, C. Payne, 2005: Lightning Relative to Storm Structure and Microphysics in TELEX. Polarimetric radar and electrical structure of a multicell storm. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, 10R.7.

MacGorman, D., 2005: Relationships among electrification, lightning, kinematics, and microphysics: Lessons from the interaction of observations and numerical storm simulations. Extended Abstracts, 2005 Annual Fall Meeting, San Francisco, CA, USA, American Geophysical Union, CD-ROM, AE32A-01.

MacGorman, D., C. L. Ziegler, E. Mansell, W. Beasley, B. Fiedler, 2005: Retrieval and assimilation of storm characteristics from both in-cloud and cloud-to-ground lightning data to improve mesoscale model forecasts. Final report to the Office of Naval Research (ONR Grant # N00014-00-1-0525) 1, 54 pp.

Manross, K. L., T. M. Smith, J. T. Ferree, G. J. Stumpf, 2008: An on-demand user interface for requesting multi-radar, multi-sensor time accumulated products to support severe weather verification. Extended Abstracts, 23rd Conference on Interactive Information Processing Systems, New Orleans, LA, USA, AMS, P2.13.

NSSL has a long history of developing radar based applications and algorithms intended to aid forecasters in warning decision making. With the advent of the WDSSII system, new and more robust algorithms are being developed in short amounts of time. Thanks to the GIS-based Google Earth application, NSSL has been able to display real-time algorithm output via the World Wide Web for feedback on these algorithms. As a result, many of these algorithms have not only proven useful and accurate, but also popular, particularly in short-term post-event storm survey and verification situations. Time accumulated Maximum Expected Size of Hail ("MESH") and time accumulated radar detected maximum low-altitude rotational shear ("Rotation Tracks") are two products that seem to be particularly useful. The latter has been used to aid forecasters in tornado damage surveys performed by National Weather Service (NWS) personnel at numerous Weather Service Forecast Offices. Emergency managers may also find these plots useful for disaster response.

Currently these data are continuously being produced on the CONUS scale and are stored in a short term archive (up to one week). For specific events, or by request, the data can be manually reprocessed for smaller regions and short time scales and are occasionally archived indefinitely. A recently funded proposal has allowed for automated, on-demand requests of these products by end-users. Forecasters may specify region-specific GIS-encoded data for requested time periods using a web-based graphical user interface. This paper details this process as well as explaining the user interface.

Available online at ://http://ams.confex.com/ams/88Annual/techprogram/paper_134621.htm.

Manross, K. L., J. G. LaDue, 2006: New Features of the VCPExplorer: Simulated Precipitation. Extended Abstracts, 22nd International Conference on Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, American Meteorological Society, CD-ROM, 2.11. [Available from Kevin L. Manross, NSSL, 1313 Halley Circle, Norman, OK, USA, 73069.]

The VCPExplorer is an instructional tool that aides in the visualization of radar scanning strategies, including radar beam propagation path relative to terrain, and radar algorithm dependence on volume coverage pattern (VCP). The VCPExplorer has been used in the Warning Decision Training Branch's (WDTB) Advanced Warning Operations Course (AWOC) and has been upgraded with several new features to simulate radar sampling issues of precipitation. Among the new features are radar estimated rainfall. The user can modify several parameters including ZR relationship, VCP, and reflectivity profile and compare the radar estimated (based on VCP and terrain-based hybrid scan) rainfall to the "true" (based on radar reflectivity at the Earth's surface) rainfall. Other new features include simulated "bright-banding" and sub-cloud evaporation effects on radar reflectivity.

Available online at ://http://ams.confex.com/ams/Annual2006/techprogram/paper_104425.htm.

Manross, K. L., J. G. LaDue, G. Stumpf, 2005: The Volume Coverage Pattern Explorer: A new tool for visualizing radar beam paths. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, CD-ROM, 5.5.

Ortega, K. L., T. M. Smith, G. J. Stumpf, 2006: Verification of multi-sensor, multi-radar hail diagnosis techniques. Preprints, Symposium on the Challenges of Severe Convective Storms, Atlanta, GA, USA, American Meteorological Society, CD-ROM, P1.1.

Ortega, K. L., T. M. Smith, K. A. Scharfenberg, 2006: An analysis of thunderstorm hail fall patterns in the Severe Hail Verification Experiment. Preprints, 23rd Conference on Severe Local Storms, St. Louis, MO, USA, AMS, CD-ROM, P2.4.

Available online at ://http://ams.confex.com/ams/23SLS/techprogram/paper_115441.htm.

Ortega, K. L., T. M. Smith, G. J. Stumpf, J. Hocker, L. López, 2005: A comparison of multi-sensor hail diagnosis techniques. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, P1.11.

Payne, C., T. J. Schuur, D. R. MacGorman, W. D. Rust, M. Biggerstaff, K. Kuhlman, E. Bruning, N. Lund, 2008: Electrical and polarimetric radar observations of an HP supercell on 29 May 2004 during TELEX. Preprints, 3rd Conference on Meteorological Applications of Lightning Data, New Orleans, LA, USA, American Meteorological Society, 4.6.

Rabin, R. M., T. J. Schmit, 2006: Estimating soil wetness from the GOES sounder. Journal of Atmospheric and Oceanic Technology, 23, 991-1003.

Rabin, R. M., T. Whittaker, 2006: Tool for Storm Analysis Using Multiple Data Sets. Advances in Visual Computing, G. Bebis, R. Boyle, D. Koracin, B. Parvin, Ed(s)., Springer, 571-578.

Rabin, R. M., 2005: Tool for storm analysis using multiple data sets. Published in "Advances in Visual Computing", Lecture Notes in Computer Science (#3804), Bebis et. al, Editors. Published by Springer.. Proc. First International Symposium on Visual Computing., Lake Tahoe, NV, USA, University of Nevada-Reno, Desert Research Institute, Berkeley L, 571-578. [Available from Robert Rabin, 120 David L. Boren, Norman, OK, USA, 73072.]

Available online at ://http://www.springeronline.com.

Ramig, N., D. MacGorman, D. Rust, T. Schuur, P. Krehbiel, W. Rison, T. Hamlin, J. Straka, M. Biggerstaff, 2007: Relationship between lightning location and polarimetric radar signatures in an MCS. Preprints, 13th International Conference on Atmospheric Electricity, Beijing, China, IUGG/Commission on Atmospheric Electricity, PS5-2.

The relationship of lightning initiation and structure to the storm microphysics and structure depicted by polarimetric radar has been analyzed for a small mesoscale convective system (MCS) that occurred on 19 June 2004 during the Thunderstorm Electrification and Lightning Experiment (TELEX). Horizontal reflectivity (Z), differential reflectivity (Zdr), specific differential phase (Kdp) and correlation coefficient (ρHV) data were gathered by a 10-cm, polarimetric radar located in Norman, Oklahoma. Three-dimensional lightning structure was mapped by the Oklahoma Lightning Mapping Array (OK-LMA), and ground strike points were mapped by the United States National Lightning Detection Network. OK-LMA data were processed to group mapped points into flashes and to determine the initiation location of each flash that contained more than 10 mapped points. The initiation location was calculated by sequentially eliminating outliers among the first 10 points that occurred in a flash, with no fewer than 5 points being used in the final initiation location. The initiation location and mapped points for each flash were superimposed on polarimetric radar data in order to investigate lightning relationships with storm structure. The lightning initiation points tended to cluster together in one of two altitude ranges and were almost all in the convective line. Initial results show a relationship between the lightning initiation locations and radar signatures in both Z and Kdp. In the lower altitude range, between 3 and 5 km MSL, initiation locations tended to cluster around updraft cores, in regions characterized by a transition in Z from 50 to 55 dBZ and a transition in Kdp from 0.4 to 0.5 deg/km. In the upper range, between 8 and 10 km MSL, initiation points tended to cluster directly above the updrafts, in regions characterized by a transition in Z from 42.5 to 47.5 dBZ and in Kdp from 0.075 to 0.150 deg/km. The two-layer nature of the initiation points is consistent with grossly tripolar structure of the charge distribution involved in lightning in the convective line. Also, the horizontal pattern of the initiation locations has a quasi-periodic horizontal structure which is 180 degrees out of phase with the maximum updraft locations for the lower region and is in phase with the maximum updraft locations for the upper region. There were also a few flash initiations within the stratiform region, possibly associated with decaying cells. The values of Z and Kdp associated with these initiation points were smaller than in the convective line, but as in the convective line, the initiations also occurred along gradients, above a local maximum, in these parameters.

Ramig, N., D. MacGorman, W. D. Rust, T. J. Schuur, E. Bruning, P. Krehbiel, W. Rison, T. Hamlin, J. Straka, C. Payne, I. Apostolakopoulos, M. Biggerstaff, N. Biermann, L. Carey, 2005: The stratiform region of an MCS on 19 June in TELEX 2004 observed with polarimetric and Doppler radars, electric field soundings, and a lightning mapping array. Preprints, AGU Fall Meeting, San Francisco, CA, USA, American Geophysical Union, AE21A-0977.

Scharfenberg, K., T. M. Smith, C. Legett, K. L. Manross, K. L. Ortega, A. G. Kolodziej, 2008: NSSL's prototype enhanced severe thunderstorm database. Extended Abstracts, 24th Conf. on IIPS, New Orleans, LA, USA, Amer. Meteor. Soc., 5C.1.

Scharfenberg, K. A., K. L. Elmore, T. J. Schuur, C. Legett, 2007: Analysis of dual-pol WSR-88D base data collected during three significant winter storms. Preprints, 31st Intl. Conf. on Radar Meteor., Cairns, Australia, Amer. Meteor. Soc., CD-ROM, P10.10.

Base data from a dual-pol WSR-88D radar collected during three significant winter storms in Oklahoma are examined. These cases (29-30 November 2006, 12-14 January 2007, and 20 January 2007) were chosen due to concurrent collection of high-resolution surface precipitation type reports near the radar (see paper by Elmore, Scharfenberg, and Legett). Large temporal and spatial variabilities in precipitation types were observed during these events as revealed by the surface reports. This paper will focus on radar data collected during these periods of large variability. Associating the evolution of the radar data and the surface reports is critical for future enhancements to automated hydrometeor classification and to successful forecast decision-making during winter storms.

Available online at ://http://ams.confex.com/ams/pdfpapers/123618.pdf.

Scharfenberg, K. A., D. W. Burgess, M. J. Istok, K. L. Manross, R. Murnan, P. T. Schlatter, 2007: Product development and evaluation for the dual-pol WSR-88D radar. Preprints, 31st Intl. Conf. on Radar Meteor., Cairns, Australia, Amer. Meteor. Soc., CD-ROM, 10.2.

The United States' WSR-88D weather radar network is expected to be upgraded to include dual-polarimetric capabilities over the next several years. This upgrade is presumed to improve echo classification, precipitation rate estimation, and overall data quality. Numerous dual-pol WSR-88D data sets from a prototype radar in Norman, Oklahoma have been collected. Seven sample dual-pol WSR-88D datasets were distributed to operational users of WSR-88D radar data throughout the United States. These cases were chosen to cover a variety of high-impact weather events, including significant winter storms, severe thunderstorms, mixed precipitation phases, and heavy rainfall. Low-to-moderate-impact weather events were also chosen, including light to moderate rain and light snow events. Finally, the data were chosen to include meteorological echoes at various ranges from the radar as well as non-meteorological echoes. The evaluators were asked to provide feedback on the sample dual-pol base products (differential reflectivity, correlation coefficient, differential phase shift, and specific differential phase shift) and associated algorithms (hydrometeor classification, filtered reflectivity, and quantitative precipitation estimation). The results of the collected feedback are discussed in this paper, along with implications for operational forecasting, warning decision-making, product visualization, and training requirements.

Available online at ://http://ams.confex.com/ams/pdfpapers/123618.pdf.

Scharfenberg, K. A., 2006: Development and testing of a dual-pol-based surface precipitation type algorithm. Preprints, 12th Conf. on Aviation, Range, and Aerospace Meteor., Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, P6.2.

An algorithm to integrate data from surface temperature sensors, numerical weather prediction model thermodynamic output, and dual-polarimetric radar hydrometeor classification algorithm output and produce a surface precipitation type product is described. Results from initial tests on a few archived cases are presented. Although sufficient verification data sets are not yet available, this technique shows promise in accurately depicting regions of freezing rain, snow, and rain at the surface, aiding aviation ground operations during winter storms.

Scharfenberg, K. A., T. M. Smith, G. J. Stumpf, 2005: The testing of NSSL multi-sensor applications and data from prototype platforms in NWS forecast operations. Preprints, 21st Conference on Weather Analysis and Forecasting, Washington, DC, USA, American Meteorological Society, 6A.2.

Scharfenberg, K. A., V. Lakshmanan, S. E. Giangrande, 2005: Development and testing of polarimetric radar applications in WDSS-II. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, CD-ROM, 5.1.

Scharfenberg, K. A., D. J. Miller, T. J. Schuur, P. T. Schlatter, S. E. Giangrande, V. M. Melnikov, D. W. Burgess, D. L. Andra, Jr., M. P. Foster, J. M. Krause, 2005: The Joint Polarization Experiment: Polarimetric radar in forecasting and warning decision-making. Weather and Forecasting, 20, 775-788.

To test the utility and added value of polarimetric radar products in an operational environment, data from the Norman, Oklahoma (KOUN), polarimetric Weather Surveillance Radar-1988 Doppler (WSR-88D) were delivered to the National Weather Service Weather Forecast Office (WFO) in Norman as part of the Joint Polarization Experiment (JPOLE). KOUN polarimetric base data and algorithms were used at the WFO during the decision-making and forecasting processes for severe convection, flash floods, and winter storms. The delivery included conventional WSR-88D radar products, base polarimetric radar variables, a polarimetric hydrometeor classification algorithm, and experimental polarimetric quantitative precipitation estimation algorithms. The JPOLE data collection, delivery, and operational demonstration are described, with examples of several forecast and warning decision-making successes. Polarimetric data aided WFO forecasters during several periods of heavy rain, numerous large-hail-producing thunderstorms, tornadic and nontornadic supercell thunderstorms, and a major winter storm. Upcoming opportunities and challenges associated with the emergence of polarimetric radar data in the operational community are also described.

Scharfenberg, K. A., K. L. Elmore, E. Forren, V. Melnikov, D. S. Zrnic, 2005: Estimating the impact of a 3-dB sensitivity loss on WSR-88D data. Preprints, 32nd Conf. on Radar Meteorology, Albuquerque, NM, USA, Amer. Meteor. Soc., CD-ROM, P12R.9.

The planned upgrade of the WSR-88D network to include dual-polarimetric capabilities is expected to result in a loss of about 3 dB in sensitivity per channel. In order to better estimate the impact of this sensitivity loss, case study and real-time simulations were performed.

Algorithm products and base data from six archive WSR-88D cases were examined. The proportion of reflectivity samples lost upon desensitization was calculated, and the visibility of important meteorological features and velocity dealiasing errors before and after the desensitization were noted. Changes in the outputs of the echo top, hail detection, and legacy mesocyclone algorithms were observed. Changes to the output of the VAD wind profile (VWP) algorithm were measured. These results are presented.

In addition, a 3 dB higher threshold then usual was applied to KTLX WSR-88D data to simulate the signal loss. This data was then made available to National Weather Service forecasters for a side-by-side evaluation during the spring 2005 convective season. Forecaster feedback was compiled to estimate the impact of the sensitivity loss on situation awareness and decision-making, and these results are discussed.

An overview of proposed mitigation techniques to recover some of the lost velocity information is presented.

Available online at ://http://ams.confex.com/ams/pdfpapers/96931.pdf.

Smith, T. M., V. Lakshmanan, 2008: Real-time and recent historical weather data in Google Earth. Extended Abstracts, 23rd Conference on Interactive Information Processing Systems, New Orleans, LA, USA, AMS, 9B.6.

The National Severe Storms Laboratory (NSSL) utilizes Google Earth as one of several ways to share experimental severe weather products with other researchers and operational meteorologists for evaluation and feedback. A variety of multi-sensor severe weather products are generated by NSSL and shared to Google Earth users via the internet at http://wdssii.nssl.noaa.gov. These products include spatially gridded fields of Vertically Integrated Liquid, Maximum Expected Hail Size, tracks of circulations derived from Doppler velocity data, composite reflectivity, and 30-to-60 minute forecast reflectivity fields, among others. These products, which have a spatial resolution of approximately 1 km by 1 km, are generated every one to five minutes within the Warning Decision Support System – Integrated Information (WDSS-II). The WDSS-II system provides the images in GeoTIFF format which may be imported into most Geographic Information Systems software including virtual globes such as Google Earth.

During the first two years these data have been provided on the internet, they have been used to improve the verification of severe weather events as well as in disaster response and post-event damage assessments. This presentation focuses on the scientific and educational uses of virtual globes to interrogate real-time and archived severe weather products.

Available online at ://http://http://ams.confex.com/ams/88Annual/techprogram/paper_134923.htm.

Smith, T. M., P. L. Heinselman, D. Priegnitz, 2007: Characteristics of microburst events observed with the National Weather Radar Testbed phased array radar. Preprints, 23rd Conference on Interactive Information Processing Systems, San Antonio, TX, USA, AMS, CD-ROM, 7.8.

Microbursts are small-scale (< 4 km diameter) outflows induced by strong downdrafts in thunderstorms that frequently cause damage to property and are a hazard to aviators. Many severe microbursts originate from storm cells that form in regions of moderate-to-high Convective Available Potential Energy (CAPE), weak environmental shear, and environments that are highly unstable to downdraft formation. These storm cells typically have a life cycle of 20-40 minutes, which makes them very difficult to predict.

Automated algorithms that analyze radar data and make short-term predictions for microburst events, as well as detecting low-altitude divergence signatures associated with their outflows, have been implemented for WSR-88D and TDWR systems. These applications rely on microburst “precursors” that may be observed at the higher altitudes of a storm shortly preceding the outflow at the surface to make short-lead-time forecasts of a microburst event. However, microburst events evolve rapidly, and because these radars typically only sample the upper portions of a storm once every 4 to 6 minutes (depending on scanning strategy), they may not sample key precursor features aloft or the near-surface outflow.

This presentation examines damage-producing severe microburst events that occurred in Central Oklahoma during July 2006 that were observed with the National Weather Radar Testbed (NWRT) Phased Array Radar (PAR). These storms formed within 50 km of the PAR site and were sampled with a temporal resolution of 15 to 30 seconds. We will compare the PAR observations of the storms with the KTLX WSR-88D, OKC TDWR, and multi-radar, multi-sensor information from the Warning Decision Support System – Integrated Information.

Available online at ://http://ams.confex.com/ams/pdfpapers/120074.pdf.

Smith, T. M., K. L. Ortega, A. G. Kolodziej, 2007: Enhanced, high-density severe storm verification. Preprints, 23rd Conference on Interactive Information Processing Systems, San Antonio, TX, USA, AMS, CD-ROM, 4B.3.

The Severe Hail Verification Experiment (SHAVE) was conducted during May through August of 2006. Researchers in SHAVE combined radar and environmental information available from the National Severe Storms Laboratory's Warning Decision Support System – Integrated Information (WDSS-II) with geographic information available in Google Earth and other sources. This information was used to identify locations to make targeted telephone calls to the public in regions where storms occurred within minutes of an event in order to collect information about the occurrence, size, and duration of hail. During the experiment, hail swaths from severe thunderstorms were documented at a much higher spatial and temporal resolution than is available in the National Climate Data Center's Storm Data publication and in National Weather Service (NWS) local storm report products.

The presentation shows results from SHAVE and compares the independently collected, high-resolution data with traditional NWS verification data for hail, and discusses the uncertainties associated with both data sets. We discuss the benefits of the improved verification data and their implications for warning verification and future changes in the NWS warning paradigm, such as “warning polygons” and probabilistic threat area warnings. We also consider improvements to the data collection methodologies and the expansion of the experiment in 2007 to include the analysis of severe wind events and other threats.

Available online at ://http://ams.confex.com/ams/pdfpapers/120091.pdf.

Smith, T. M., V. Lakshmanan, 2006: Utilizing Google Earth as a GIS platform for weather applications. Preprints, 22nd Conference on Interactive Information Processing Systems, Atlanta, GA, USA, AMS, CD-ROM, 8.2.

Available online at ://http://ams.confex.com/ams/Annual2006/techprogram/paper_104847.htm.

Smith, T. M., K. L. Ortega, K. A. Scharfenberg, K. M. Manross, A. Witt, 2006: The Severe Hail Verfication Experiment. Preprints, 23rd Conference on Severe Local Storms, St. Louis, MO, USA, AMS, CD-ROM, 5.3.

Available online at ://http://ams.confex.com/ams/23SLS/techprogram/paper_115436.htm.

Smith, T. M., G. J. Stumpf, 2005: Multi-sensor storm cell identification and analysis. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, P1.10.

Vasiloff, S. V., D. J. Seo, K. H. Howard, J. Zhang, D. H. Kitzmiller, C. Coauthors, 2007: Improving QPE and Very Short Term QPF. Bulletin of the American Meteorological Society, 88, 1899-1911.

Vasiloff, S. V., K. H. Howard, 2007: Investigation of a severe microburst near Phoenix, Arizona as seen by a mobile Doppler radar and the KIWA WSR-88D. Extended Abstracts, 13th Conference on Aviation, Range and Aerospace Meteorology, New Orleans, LA, USA, AMS, p4.7.

Vasiloff, S. V., B. Kaney, C. Langston, W. Xia, 2007: The National Severe Storms Laboratory QPE verification system. Extended Abstracts, 24th Conference on IIPS, New Orleans, LA, USA, AMS, 6B.12.

Vasiloff, S. V., D. J. Seo, K. W. Howard, J. Zhang, D. H. Kitzmiller, M. G. Mullusky, W. F. Krajewski, E. A. Brandes, R. M. Rabin, D. S. Berkowitz, H. E. Brooks, J. A. McGinley, R. J. Kuligowski, B. G. Brown, 2007: Improving QPE and Very Short Term QPF: An Initiative for a Community-Wide Integrated Approach. Bulletin of the American Meteorological Society, 88, 1899-1911.

Accurate quantitative precipitation estimates (QPE) and very short term quantitative precipitation forecasts (VSTQPF) are critical to accurate monitoring and prediction of water-related hazards and water resources. While tremendous progress has been made in the last quarter-century in many areas of QPE and VSTQPF, significant gaps continue to exist in both knowledge and capabilities that are necessary to produce accurate high-resolution precipitation estimates at the national scale for a wide spectrum of users. Toward this goal, a national next-generation QPE and VSTQPF (Q2) workshop was held in Norman, Oklahoma, on 28–30 June 2005. Scientists, operational forecasters, water managers, and stakeholders from public and private sectors, including academia, presented and discussed a broad range of precipitation and forecasting topics and issues, and developed a list of science focus areas. To meet the nation's needs for the precipitation information effectively, the authors herein propose a community-wide integrated approach for precipitation information that fully capitalizes on recent advances in science and technology, and leverages the wide range of expertise and experience that exists in the research and operational communities. The concepts and recommendations from the workshop form the Q2 science plan and a suggested path to operations. Implementation of these concepts is expected to improve river forecasts and flood and flash flood watches and warnings, and to enhance various hydrologic and hydrometeorological services for a wide range of users and customers. In support of this initiative, the National Mosaic and Q2 (NMQ) system is being developed at the National Severe Storms Laboratory to serve as a community test bed for QPE and VSTQPF research and to facilitate the transition to operations of research applications. The NMQ system provides a real-time, around-the-clock data infusion and applications development and evaluation environment, and thus offers a community-wide platform for development and testing of advances in the focus areas.

Vasiloff, S. V., 2006: Comparison of 2 hour forecasts based on persistence and a cross-correlation technique.. Preprints, 12th Conference on Aviation, Range, and Aerospace Meteorology, Atlanta, GA, USA, AMS, CD-ROM, 3.10. [Available from steven.vasiloff@noaa.gov, National Weather Center, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

The NCAR Weather Support to Deicing Decision Making System (WSDDM) uses a cross-correlation technique to produce radar echo motion vectors. These vectors are then used to forecast snow water equivalent precipitation based on future echo positions with the focus on airports. It has been shown that WSDDM 30 min forecasts have large skill compared to persistence forecasts (a persistence forecast assumes that the current state will continue). This paper carries this type of comparative analysis out to two hours. Data from winter storms in the upper Midwest are evaluated and point forecasts near Chicago and Minneapolis are determined for both methods. Various echo configurations are used for the tests and include rain/snow bands, echoes from different sectors of synoptic cyclones and echoes with various reflectivity intensities.

Ware, E. C., D. M. Schultz, H. E. Brooks, P. J. Roebber, S. L. Bruening, 2006: Improving snowfall forecasting by accounting for the climatological variability of snow density.. Weather and Forecasting, 21, 94-103.

Accurately forecasting snowfall is a challenge. In particular, one poorly understood component of snowfall forecasting is determining the snow ratio. The snow ratio is the ratio of snowfall to liquid equivalent and is inversely proportional to the snow density. In a previous paper, an artificial neural network was developed to predict snow ratios probabilistically in three classes: heavy (1:1 < ratio < 9:1), average (9:1 <= ratio <= 15:1), and light (ratio > 15:1). A Web-based application for the probabilistic prediction of snow ratio in these three classes based on operational forecast model soundings and the neural network is now available. The goal of this paper is to explore the statistical characteristics of the snow ratio to determine how temperature, liquid equivalent, and wind speed can be used to provide additional guidance (quantitative, wherever possible) for forecasting snowfall, especially for extreme values of snow ratio. Snow ratio tends to increase as the low-level (surface to roughly 850 mb) temperature decreases. For example, mean low-level temperatures greater than −2.7°C rarely (less than 5% of the time) produce snow ratios greater than 25:1, whereas mean low-level temperatures less than −10.1°C rarely produce snow ratios less than 10:1. Snow ratio tends to increase strongly as the liquid equivalent decreases, leading to a nomogram for probabilistic forecasting snowfall, given a forecasted value of liquid equivalent. For example, liquid equivalent amounts 2.8–4.1 mm (0.11–0.16 in.) rarely produce snow ratios less than 14:1, and liquid equivalent amounts greater than 11.2 mm (0.44 in.) rarely produce snow ratios greater than 26:1. The surface wind speed plays a minor role by decreasing snow ratio with increasing wind speed. Although previous research has shown simple relationships to determine the snow ratio are difficult to obtain, this note helps to clarify some situations where such relationships are possible.

Available online at ://http://www.cimms.ou.edu/~schultz/pubs/wareetal06.pdf.

Witt, A., 2007: Performance of two velocity dealiasing algorithms on Terminal Doppler Weather Radar data. Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, American Meteorological Society, CD-ROM, P13A.14.

Witt, A., R. A. Brown, V. Lakshmanan, 2005: Real-time calculation of horizontal winds using multiple Doppler radars: A new WDSS-II module. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, Amer. Meteor. Soc., CD-ROM, P8R.7.

Wood, V. T., 2008: Improvement of WSR-88D VAD Winds: Cyclonic Wind Fields. Preprints, 28th Conference on Hurricanes and Tropical Meteorology, Orlando, FL, USA, AMS, P2B.3. [Available from Vincent T. Wood, 120 David L. Boren Blvd., National Severe Storms Laboratory, Norman, OK, USA, 73072.]

Hurricanes pose a serious threat to life and property along the Gulf and Atlantic coastal regions of the United States. The WSR-88D network provides the potential to improve hurricane forecasts and warnings by monitoring changes in a hurricane’s track, eye diameter, radar eyewall and rainband reflectivities. The WSR-88D Velocity-Azimuth Display (VAD) Wind Profile (VWP) display is a useful tool for diagnosis of wind fields at different altitudes as a hurricane is approaching a coastal WSR-88D.

The causes of missing winds on the VWP display were related to cyclonic flow from the approaching hurricane. The missing data arose because the extreme positive and negative Doppler velocity values around the VAD circle were inherently not 180 degrees apart and, therefore, the first-harmonic Fourier sine curve used in the operational WSR-88D VAD algorithm was a poor fit to the data. This resulted in root-mean-square (RMS) differences that exceeded the threshold value. In this situation, most of the winds on the VWP display were set equal to missing in spite of the fact that there were strong radar returns.

A new solution to recover or improve VAD winds has been developed. A higher-order polynomial regression technique employs least-squares fit of the Doppler velocity data distributed on the VAD circle. Wind speed is computed from the average of the magnitudes of the positive and negative peaks of the quasi-sine curve. Wind direction is determined from the average of the magnitudes of maximum and minimum azimuths (at which positive and negative Doppler velocity peaks occur, respectively) minus ninety degrees. After applying the experimental technique to a couple of hurricane cases such as Hurricane Katrina (29 August 2005) and Hurricane Rita (20 September 2005), the technique examines a standard deviation about a regression line which agrees well with the RMS value. The higher-order polynomial regression VAD curve fits the measurements with low RMS difference values. It is indicated that the technique does a good job of fitting the curve to the data points with low RMS difference between the curve and data points.

Wood, V. T., 2007: OK-WARN: Oklahoma Weather Alert Remote Notification. Preprints, 16th Symposium on Education, San Antonio, TX, USA, Amer. Meteor. Soc., CD-ROM P1.25.

Oklahoma Weather Alert Remote Notification (OK-WARN) is a new service that provides timely notification of weather hazards and emergencies to people with hearing loss via pager, e-mail or cell phone. This program was developed as a partnership between Oklahoma Department of Emergency Management, NOAA National Weather Service, NOAA National Severe Storms Laboratory, Oklahoma Department of Rehabilitation Services, Communication Services for the Deaf of Oklahoma, and Weather Affirmation, LLC. OK-WARN was made possible by a federal grant from the Federal Emergency Management Agency, now a division of the Department of Homeland Security. Since the inception of OK-WARN in 2001, the program has been expanded statewide to serve the deaf and hard-of-hearing community. Information about how OK-WARN operates will be presented.

Wood, V. T., 2007: Impact of Severe Weather on People with Hearing Loss. Weather and Society Watch Vol. 1, No. 4, July 20, 2007, 3 pp.

Wood, V. T., L. W. White, C. R. Alexander, R. L. Tanamachi, 2006: An analytical model of one- and two-celled vortices: Preliminary testing. Preprints, 23rd Conference on Severe Local Storms, St. Louis, MO, USA, American Meteorological Society, CD-ROM, P10.1.

Wood, V. T., R. A. Brown, D. C. Dowell, 2005: Simulated WSR-88D measurements of low-reflectivity eyes associated with tornadoes. 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, P15R.6.

Zhang, J., S. Wang, 2006: An Automated 2D Multipass Doppler Radar Volocity Dealiasing Scheme. Journal of Atmospheric and Oceanic Technology, 23, 1239-1248.

Zhang, J., K. Howard, J. J. Gourley, 2005: Constructing three-dimensional multiple radar reflectivity mosaics: examples of convective storms and stratiform rain echoes. Journal of Atmospheric and Oceanic Technology, 22, 30-42.