Effects of Surface Baroclinicity on Frontal Overrunning along the Central Gulf Coast

Abstract

Along the United States Gulf coast and over the northern Gulf of Mexico, frontal overrunning occurs frequently. Cyclogenesis over the Gulf is often associated with this type of weather system. Effects of baroclinic fields on frontal overrunning are investigated from synoptic and climatological points of view. It is found that, from October through April, the orientation of the shelf break is a very important baroclinic characteristic because fronts tend to stall there rather than at the physical coastline. To further substantiate this deduction dynamically, the local geostrophic vorticity field over the western Louisiana-upper Texas shelf region is estimated monthly. The correlation coefficient between the vorticity field and the frequency of frontal overrunning along the central Gulf coast was .86. For forecasting applications, a simple formula is provided to estimate this local vorticity from the temperature difference between Lake Charles, Louisiana, and buoy station 42002 in the deep Gulf.