NSSL Hot Item

Operational users evaluate new NSSL radar products

An upgrade to the national network of WSR-88D (NEXRAD) weather radars will be completed by 2010. The improvements will include a dual-polarization capability, allowing the radar can transmit pulses in both horizontal and vertical orientations (the WSR-88D currently only transmits horizontal pulses). Dual-polarization will provide significant improvements in rainfall estimation, precipitation classification (rain, hail, snow, sleet), and weather hazard detection.

NSSL is working to extend the effectiveness of this upgrade by developing products to assist users in operational decision-making during severe local storms, including flooding and winter storms. The products were evaluated by operational users, and results were published in a paper for the 33rd Conference on Radar Meteorology this fall.

Field evaluators consisted of a variety of users ranging from experienced users of dual-pol products to forecasters who frequently use WSR-88D data during the daily weather-related operations.

Seven dual-pol WSR-88D datasets were chosen to cover a variety of high-impact weather events including significant winter storms, severe thunderstorms, mixed precipitation phases and heavy rainfall. Evaluators were asked to provide feedback on the candidate dual-pol base products and associated algorithms to estimate how they might benefit operational meteorologists.

Positive results included:

- The “Rain/hail” category was useful to operations as a “flag” of locations where the meteorologist should further scrutinize base products

- Precipitation classification and melting layer capabilities may be very helpful in forecast operations, particularly in winter storms

- Major improvements to remote quantitative precipitation estimation are likely, particularly in flash flood warning decision making and forecasting

- Instantaneous rainfall rate information was found to be potentially useful in flash flood warning operations

Background: NSSL has been a leader and major contributor to the scientific and engineering development of polarimetric weather radar for the past 20 years.

Significance: The additional information from vertical pulses provided by dual-polarized Doppler radar will greatly improve the quality and accuracy of many different types of forecasts and warnings for hazardous weather.