Forecasting summertime convection in western North Dakota using RAOB

The North Dakota Atmospheric Resource Board (NDARB) operates a summer cloud seeding project in western North Dakota every year. Accurate forecasting is very important in making sure project personnel are prepared for any possible weather scenarios that would require action.

An attempt was made using upper air sounding and model sounding data to develop a reliable system of forecasting convection during the summer of 2007. The rawinsonde observation program RAOB was used to analyze soundings throughout the summer and a total of 77 days were evaluated. Each of the 42 indices contained in RAOB's severe weather table, with the addition of convective inhibition (CIN) were evaluated for each available sounding. The attempt was made to find a threshold for each of the indices, above or below which thunderstorms would or would not occur.

Verification of each day's forecast was accomplished using radar data from the NDARB's C-band radars in Stanley, ND and Bowman, ND and displaying the data using the Thunderstorm Identification, Tracking, Analysis, and Nowcasting (TITAN) software. Analysis of the 42 severe weather indices showed that when model soundings from 00Z were used in conjunction with certain indices very good accuracy could be obtained.