Wake Low Severe Wind Events in the Mississippi River Valley: A Case Study of Two Contrasting Events

Abstract

Severe winds, in excess of 50 kt (25 m s?1), brought widespread damage across the mid?Mississippi Valley on the mornings of 11 April 1995 and 28 April 1996. These severe winds were unusual and unexpected as they trailed behind stratiform precipitation areas where severe weather is not normally expected. The wake low on 11 April 1995 appeared to be the result of strong adiabatic warming due to dry air subsidence while the wake low on 28 April 1996 appeared to be associated with a gravity wave. Because wake lows are short-lived mesoscale phenomena, they are generally not well understood by the operational forecasting community and have been nearly impossible for forecasters to predict. With the modernization of the National Weather Service, it may become feasible to anticipate and track these mesoscale phenomena with Doppler radar, surface observations, and finer-resolution models. With an evaluation of some of the differences and similarities in the generation and maintenance of severe wake lows, operational forecasters can better understand these potentially severe phenomena and provide the public with useful information on these unusual events.