Structure of an immature cyclonic storm in the Bay of Bengal as revealed by radar

Abstract

Poorly developed or immature cyclonic storms are common in the Bay of Bengal particularly when their residence time over the sea is short. These often do not exhibit on the radar or satellite pictures all the features normally associated with tropical storms. Spiral rainbands are not stable, a complete eyewall is not formed: false eye circulations develop and probably inhibit intensification. The rainshield area consists of shallow echoes with bright bands while the spiral band and eyewall areas have tall convective clouds probably consisting of supercooled water. Observed features on radar do not give any indication of future motion.

The intensity of such immature systems is difficult to assess from observed winds owing perhaps to asymmetry of structure. They are also difficult to locate and track with the available meager synoptic data coastal radar pictures and twice-a-day satellite pictures. A specific case of radar observation of a storm of this type is examined to see how best such storms can be located, tracked and classified.