Mesoscale surface analysis of the ERICA IOP-5 cyclone.

Abstract

The mesoscale surface structure of an explosively deepening storm that developed during Intensive Observation Period (IOP) 5 (18-20 January 1989) of the Experiment on Rapidly Deepening Cyclones over the Atlantic (ERICA) was examined to determine the influence of surface forcing on explosive cyclogenesis. Aircraft, buoy and ship observations were converted to a 20 km gridded data set in order to generate objective analyses of the surface pressure and temperature fields comparable to the best hand analyses. The Brown-Liu boundary layer model was then used to calculate surface sensible heat fluxes from the gridded data sets. These analyses showed that the most significant feature that distinguished the IOP-5 storm from a typical nonexplosive storm was the region of sustained positive heat fluxes that occurred east of the low center. This feature, combined with substantial warm advection and conditions of moist symmetric neutrality in the baroclinic zone of the warm front, supports destabilization of the boundary layer and enhanced low-level baroclinicity. Thus, the positive heat fluxes fuel the convective transport of heat and moisture to the upper atmosphere and enhance the sensible and condensation heating that contribute to explosive cyclogenesis