Kristin Kuhlman
School of Meteorology
The University of Oklahoma, Norman, OK
NOAA/National Severe Storms Laboratory
17 April 2009, 2:00 PM
National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK
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A high-precipitation tornadic supercell storm was observed by multiple platforms on 29 May 2004 during the Thunderstorm Electrification and Lightning Experiment (TELEX). Observational systems included the Oklahoma Lightning Mapping Array (LMA), mobile balloon-borne soundings, and two mobile SMART-R (SR) C-Band radars. This seminar will utilize data from these platforms to relate the spatial distribution and evolution of lightning to storm kinematics and microphysics, especially to regions of microphysical charging and the location and geometry of those charge regions. One example is the relationship of the observed transient lightning hole and of large lightning densities to kinematic properties inferred from dual-Doppler analyses of the SR data.
The lightning flashes near the core of this storm, although extraordinarily frequent, tended to have shorter duration and smaller horizontal extent than typical flashes in other storms having less frequent lightning. We suggest that this is due, at least in part, to many small pockets of charge lying in close proximity to small pockets of the opposite polarity of charge. Thus, each polarity of lightning leader propagates only a relatively short distance before reaching regions of unfavorable electrical potential. In the anvil, however, lightning extended tens of kilometers from the reflectivity cores in roughly horizontal layers, consistent with the charge spreading through the anvil in broad sheets.
Previous studies of lightning in anvil clouds have reported that flashes began in or near the storm core and propagated downwind into the anvil, and many flashes followed that pattern in this storm. However, here we report the first observations of flashes that began in the anvil 30-100 km from the cores of the storms and propagated upwind back toward the cores. It had been thought that flashes could not be initiated far downwind in the anvil, because anvil charge was thought to be produced mainly in the storm’s deep updraft and to decrease with distance into the anvil. Interaction between charge regions in the two converging anvils of adjoining storms appeared to cause some of the distant flash initiations, but a local charging mechanism in the anvil likely also contributed to the flash initiations.
The above observations are compared with results from simulations using the COMMAS model with parameterizations for electrification and lightning and data assimilation of mobile radar data from SR2 using an
ensemble Kalman Filter.
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