25th Conference on Severe Local Storms


A Sounding Analog System to Produce Probabilistic Forecasts of Maximum Hail Size

Ryan E. D. Jewell, NOAA/NWS/NCEP/SPC, Norman, OK

SARS (Sounding Analog Retrieval System) is used to produce maximum hail size forecasts and conditional probability forecasts of significant (>= 2.00” diameter) hail using a calibrated sounding analog matching routine. Incorporating a historical hail proximity sounding database of more than 1100 soundings from 1989-2006, the algorithm focuses on a short list of convective parameters that has been found to show skill in delineating between hail sizes across the reporting spectrum. To determine the appropriate range magnitudes, SARS independently tests each sounding against the rest of the database, resulting in tens of thousands of parameter range combinations. The list of analog matches for every proximity sounding (each with a known maximum hail size report) is analyzed. The particular parameter range combination that achieves the highest statistical correlation between forecast and observed hail size is used in the “SARS Hail Size” algorithm, while another calibration is done to produce the most skillful probabilistic forecast of significant hail (conditional on severe hail of any size occurring). The SARS method can be modified for use with other types of weather phenomena, such as supercells vs. non-supercells (or tornadic vs. non-tornadic), severe wind, heavy rain, etc, so long as a high quality historic dataset has been compiled.

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Session 4B, Forecasting Techniques and Warning Decision Making: Short-Range Forecasting I
Monday, 11 October 2010, 4:30 PM-6:00 PM, Grand Mesa Ballroom D

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