VAS Retrievals as a Source of Information for Convective Weather Forecasts: An Objective Assessment and Comparison with Other Sources of Upper-Air Observations

Abstract

Abstract Objective experiments have been carried out to determine which moisture and stability indices as derived from the VISSR Atmospheric Sounder (VAS) contain the greatest amount of predictive information with respect to thunderstorm and severe local storm events. In these experiments, stability and moisture parameters derived from 1700 UTC VAS retrievals were compared and correlated to storm observations made during the subsequent 2000–0000 UTC period. The amount of predictive information in these indices was also compared to that possessed by indices derived from VAS first-guess profiles, concurrently available rawinsonde measurements, and numerical model forecasts. The correlation in the form of the computed information ratio (Ic) was used as a measure of predictive power in these experiments. It was found that precipitable water and modified versions of the classic K index which included recent surface data had the highest values of Ic for general thunderstorm occurrence. The 50-kPa gradient wind ...