Tropical low formation and intensification over land as seen in ECMWF analyses

Abstract

Case studies of the formation and intensification over land of three tropical lows in northern Australia are described. The case studies are based on European Centre for Medium-Range Weather Forecasts (ECMWF) analyses. The aim is to investigate the generality of recent results concerning the dynamics and thermodynamics of tropical lows. Consistent with these results, it is found that the processes of low formation and intensification are the same over land as over the ocean. An important element of the intensification process is the need for bursts of deep convection to persist near the circulation centre, which, in turn, requires that convective instability be maintained by surface moisture fluxes. The moist monsoonal environment locally surrounding the storm provides a shield against the adverse effects of dry-air intrusion from the Australian continent.