Convection Initiation Associated with a Sea-Breeze Front, a Gust Front, and Their Collision

The initiation of convection associated with a sea-breeze front, a gust front, and their collision is analyzed using data collected in east-central Florida during the Convection and Precipitation/Electrification project. In conjunction with satellite, surface, and rawinsonde information, dual-Doppler radar-derived winds are used to determine the three-dimensional kinematic factors critical to storm development. The gust front, which emanated from storms on the western half of the peninsula, propagated more rapidly and was deeper than the sea-breeze front, which originated from the east coast and was characterized by a distinctly scalloped appearance. Convection associated with the sea-breeze front appeared to develop preferentially at the vertices of this scalloped pattern where there were enhanced regions of convergence and upward motion. On the gust front, a Helmholtz shearing instability produced an organized configuration of convergence and updraft maxima along its length. However, these were not favored areas for convection initiation as storms originated ahead of the gust front in the form of low intensity reflectivity maxima (believed to be clouds forming on horizontal convective rolls), which rapidly grew in size and intensity once intercepted by the boundary. Contrary to past studies, convective activity and frontal updrafts were not enhanced after the collision of the gust front and sea-breeze front. While the magnitude of convergence at low levels increased, its depth decreased, which led to updraft intensifies similar to those before the collision. The implications of this study to the nowcasting of convection and possible areas of future research are discussed.