An Objective Method for Forecasting Thunderstorms at Truax Field, Madison, Wisconsin 1

Abstract

Thunderstorm activity at Madison is frontal or found in association with fronts. The objective method derived to forecast thunderstorms determines first the air mass favorable for the occurrence of thunderstorms and secondly if there is a front within 24 hr of Madison to release the latent instability needed to produce the thunderstorm. The air-mass predictors used are (1) the Showalter Stability Index, (2) the freezing level and (3) the surface dew-point temperature at Madison. The synoptic (frontal) predictors used are (1) the difference in surface temperatures and surface dew-point temperatures, Madison minus LaCrosse, (2) the surface wind direction at Madison and (3) the three-hour pressure tendency at Madison. The method derived is for each of the summer months June, July and August. Five years of data were used for the development of each month, and two years of data were set aside for its test. Four scatter diagrams were developed for each month from which, within minutes each morning, a forecaster can obtain a dependable “YES” or “NO” forecast of thunderstorm activity at Madison without reference to his normal techniques and procedures used to forecast thunderstorms. The results for June, July and August based on two years data each are the following per cent correct/skill scores: 87/0.59, 91/0.62, 91/0.76, respectively.