A Subsynoptic Study of Winter Cold Fronts in Florida

Abstract

Kinematic aspects of winter cold fronts in Florida are examined for a subsynoptic scale representing the frontal wind shift at the earth's surface. Fifteen selected cold fronts are studied by using time series of surface wind observations for Miami, Fla. With the aid of frontal movements estimated from six-hourly synoptic charts, the spatial wind distribution near the frontal wind shift is obtained by transforming time series observations into space series. The study of steady wind regimes ahead and behind the front indicates that the major wind change across the front occurs only in the v-component. As measured along a direction perpendicular to the front (136°T), this major change occurs over a distance of about 140 km, corresponding to a time scale of about 4.5 h. Divergence and vorticity estimates are based upon the subsynoptic wind distribution. These estimates are similar to those found previously for non-frontal subsynoptic studies on moist convection in Florida. It is found that our estimates can be roughly approximated by the spatial derivative of the v-component.