Pre-monsoon thundershowers will spread out even more over Kerala and parts of Tamil Nadu and Karnataka from next week, model forecasts indicate.
A helpful trough (a line of lower pressure) extended from Telangana to South Tamil Nadu across Rayalaseema on Monday, an India Met Department update said. The trough will stay for the most part going forward, though varying in its alignment on a day-to-day basis.
Winds blowing in
The trough is created by warm air over the surface rising into the higher levels of the atmosphere, creating lower pressure. Winds from the Arabian Sea and the Bay of Bengal blow into this space, rise in turn and cool to drop down as thundershowers.
Moderate to heavy thundershowers are being reported from many parts of Kerala, Tamil Nadu and Karnataka. This is forecast to gain further intensity later during this week and into the next.
During the 24 hours ended Monday morning, Kannur in Kerala reported rainfall of 9 cm.
Cloud cover up
Earlier, expert forecaster and monsoon researcher PV Joseph had told BusinessLine that from around May 10, a band of rain clouds would form over the South Arabian Sea and progressively increase its area over coverage.
Satellite maps on Monday showed a huge bank of clouds extending from below the equator into the Maldives and reaching up into the South Arabian Sea.
This process of cloud-building will continue, likely leading to the onset of the South-West monsoon over Kerala in the last week of May, ahead of the normal June 1 timeline.
The US National Centres for Environmental Prediction has largely endorsed this outlook, signalling a steady increase in rainfall over coastal Kerala, adjoining Karnataka and Tamil Nadu during the week starting May 16.