The Mesoscale Interaction of a Lake Breeze and Low Level Outflow from a Thunderstorm

Abstract

In the summer of 1964 a program was initiated to observe physical and dynamical characteristics of the lake breeze at a site on the eastern side of Lake Michigan. Lake breeze development and progress inland was observed by periodic pilot balloon measurements in a vertical plane perpendicular to the lakeshore. During the afternoon of 22 July, while the lake breeze was still intensifying, a thunderstorm crossed the line of observing stations. Low level outflow from the thunderstorm displaced the lake breeze and dominated the local flow regime for more than two hours after outflow was first observed. The development and interaction of the lake breeze and thunderstorm flow patterns are shown through an analysis of the wind component normal to the shoreline. A significant feature of this lake breeze system, as of others to be reported on more fully later, is the occurrence of a pronounced return current aloft. Such strong return current are not often found above sea breezes.