Evaluation and Comparison of Nowcasting Techniques/System for Convective Storms

Jim Wilson

The emphasis of this talk is the nowcasting of convective storms. Extrapolation of observations particularly radar has been the primary method for nowcasting (≤
6 h) convective storms. Extrapolation of radar echoes has been around for over 50 years and has become quite mature. As many as 30 years ago the UK Met Office was operationally blending numerical and extrapolation forecasts to make forecasts for 0-6 hr period. During the past 20 years highly observation dominated nowcasting systems have emerged which use conceptual models of storm evolution, heuristic forecasting rules, and the use of fuzzy logic techniques to combine predictors. These techniques will be briefly discussed.

There have been two international nowcasting demonstrations, both associated with the summer Olympics and a number of research demonstrations and operational tests using a variety of these techniques. The skill of these different techniques is discussed. The major limiting factor to improving skill in the 2-6 hr period is the need for greater skill in numerical weather prediction. From the authors perspective comments will be made on where improvements are needed in numerical weather prediction to improve forecasts on the nowcasting time and space scale.