Development of a Sounding-Based Prediction Model for Phoenix, Arizona

The summer season across the lower deserts of south-central Arizona is notorious for extreme weather. Excessive heat, severe thunderstorms, and flash flooding are all common occurrences. Emphasis on excessive heat awareness has increased over the past several years, which increases the importance of reliable maximum temperature forecasts. Thunderstorms associated with the North American Monsoon are often extremely difficult to predict, with subtle changes in atmospheric conditions resulting in dramatic day-to-day variability in storm intensity and areal coverage of measurable precipitation.

Two primary goals of this study are: 1) provide additional guidance to forecasters in the form of a sounding-based prediction model, and 2) determine the meteorological variables derived from a single sounding that are significant predictors of maximum temperature, minimum dew point, probability of precipitation, and quantitative precipitation amounts at Phoenix, Arizona. Data input sources for the period 2001-2007 included SRP experimental upper air soundings, ASOS observations, and the Flood Control District of Maricopa County ALERT rain gauge network. Stepwise regression methods, based off historical observations, were employed to determine statistically significant predictors for each forecast variable. Analysis of prediction model performance during summer 2008 will be presented, and planned improvements to the prediction model will be discussed.