Monday, 12 January 2009
The utility of basic parameters in the evaluation of WRF forecasts of tornadic and nontornadic outbreaks when initialized with synoptic-scale input
Hall 5 (Phoenix Convention Center)
Forecasters frequently analyze predicted and observed severe weather parameters to assess severe weather environments and to determine the types of severe weather that will occur in specific regions. However, numerous studies have suggested that certain synoptic and subsynoptic environments may favor particular convective modes and/or outbreak types. Thus, an analysis of “basic” parameters, such as geopotential height, wind speed and direction, dew point temperature (or relative humidity), etc., at various levels of the atmosphere may be very useful in the prediction of severe weather.
The analysis of these basic parameters, both subjectively and objectively, using simulations of 50 tornado outbreaks and 50 primarily nontornadic outbreaks from the Weather Research and Forecasting mesoscale model (WRF), initialized with synoptic-scale data, will be presented. Results indicate that geopotential heights and wind speeds/directions, especially in the low levels of the atmosphere, can be used to distinguish outbreaks consistently. Compared to various severe weather parameters, the analysis of forecast wind and pressure/height fields may be as helpful, or more helpful, in the correct discrimination of outbreak type, given that an outbreak of severe weather occurs.