Synoptic environment of composite tropical cyclones in the south-west Indian ocean

Abstract

The composite structure of the tropical cyclone (TC) environment in the South-West Indian Ocean is analysed using European Community medium-range weather data. Conditions suitable for the development of tropical cyclones are present between 5 and 15°S and between 40 and 100°E. Groups of westward-moving and polewardrecurving TCs are used to construct system-following composites from three days before maximum intensity to
one day after. The synoptic fields surrounding the westward-moving composite TC remain steady, whereas the recurving composite environment supports rapid vortex growth. Interaction with a subtropical trough is prominent
in the recurving TC. The results offer useful insights to weather interactions in the South-West Indian Ocean.