The estimated environment for each severe report is based on hourly 40km horizontal resolution RUC analysis data above the surface combined with objectively analyzed surface observations using RUC surface conditions as a first guess. These grid point data are analyzed for a variety of kinematic, thermodynamic, and severe weather focused diagnostic fields using the NSHARP sounding analysis program. Environmental conditions are assigned from the nearest analysis grid point at the closest hourly time prior to the observed severe weather. For the two year period, this database contains environmental estimates for over 50,000 reports. The data are then stratified and analyzed based on report intensity, location, and environmental characteristics.
Preliminary results for the 25,000 reports observed during 2005 illuminate the diverse nature of the severe storm environmental parameter space. Bi-monthly and annual average continental United States plots of mean environmental conditions associated with subclasses of severe weather reports are used to more completely document the seasonally varying regional severe weather environments such as the southeast U.S. cool season low-CAPE / high shear tornado events, low-CAPE / high-shear events associated with warm season tropical systems, and low shear / high-CAPE pulse-severe warm season events. While statistical plots and national maps of reports associated with specific environments reaffirm some previous relationships, they also reveal new complexities and limitations of this knowledge when applied to forecasting severe storms nationwide. For example, the results indicate a strong association between significant tornadoes and environments with 100 mb mixed-layer CAPE less than 1200 Jkg-1, 0-6 km shear greater than 18ms-1, 0-1 km shear greater than 10ms-1, and LCL's less than 1000m. However, this multi-variant relationship becomes more complex for significant tornadoes occurring in environments with CAPE greater than 1500 Jkg-1, which are characterized by a much wider range of shear and LCL values.