The severe thunderstorm forecasting component of the 2010 NOAA Hazardous Weather Testbed spring experiment

The NOAA Hazardous Weather Testbed, organized by the Storm Prediction Center (SPC) and National Severe Storms Laboratory (NSSL) to test and evaluate emerging scientific concepts and technologies for improved analysis and prediction of hazardous mesoscale weather, conducted the 2010 Spring Forecasting Experiment from May 17 through June 18. The experiment focused on application of cutting edge numerical weather prediction systems from a number of modeling centers (NSSL, CAPS, EMC, NCAR, GSD) run at 1-4 km grid length over CONUS domains to address high impact convective weather forecasting challenges, including severe thunderstorms producing tornadoes, large hail, and damaging winds, along with QPF/heavy rain and aviation impacts. This paper provides details of experimental forecasting and evaluation activities within the severe convective storm component of the HWT; companion papers submitted to the conference provide an overview of the HWT, details of the QPF/heavy rain and aviation impacts components, aspects of experimental models including the CAPS 26 member Storm Scale Ensemble Forecast System (SSEF), and objective verification methods developed for the HWT.

Experimental activities were designed to test the utility of unique convective storm output fields (such as simulated reflectivity, updraft helicity and speed, vertically integrated graupel, and surface wind speed) from various deterministic models and the SSEF in a simulated operational forecasting environment. This was accomplished through the issuance of daily real time probabilistic severe weather forecasts valid for late afternoon and evening time periods, and next day subjective evaluations. “Preliminary” forecasts were issued in the morning utilizing guidance from 00 UTC experimental models including probabilistic guidance from the SSEF, supplemented by operational model guidance and observational data. A “final” updated forecast was issued by mid-afternoon incorporating later model runs (especially the hourly High Resolution Rapid Refresh – HRRR) and observational data.

A number of focused evaluation tasks were designed to help identify specific sensitivities of model performance, such as the impact of radar and other data assimilation on convective forecasts, and model storm sensitivity to horizontal resolution and microphysics parameterizations, and to assess the utility of various statistical processing approaches and creation of probabilistic storm guidance from the SSEF. Descriptions of the daily severe storm experimental forecasting and evaluation activities are presented, including findings on model performance and potential value of experimental guidance products to operational severe storm forecasting.