The India Met Department said that seasonal rains would reach Nicobar Islands, South Andaman Sea and parts of South Bay of Bengal during this phase.
From here, it will normally take another 10 to 12 days for the rain system to reach Kerala and announce arrival over mainland India. The Met is expected to announce the date of onset over Kerala shortly.
It has maintained a watch for a rain-driving low-pressure area (‘low’) to form off Sri Lanka coast by Saturday. It expects the system to intensify twice over into a monsoon depression by Monday.
The arrival of a storm-building Madden-Julian Oscillation (MJO) wave has made all the difference to the weather conditions evolving over the South Arabian Sea and adjoining South-West Bay of Bengal.
The MJO wave transits the Indian Ocean high in the atmosphere periodically from West to East and is known to set up storms (‘low,’ depression and even cyclones) apart from triggering monsoon onsets.
Rain for TN, Kerala
The US National Centre for Environmental Prediction has forecast heavy rainfall over Kerala and Tamil Nadu from for week ending May 21.
The European Centre for Medium-Range Weather Forecasts says that the brewing ‘low’ envelop Sri Lanka in a torrent of rainfall before entering Tamil Nadu and later Kerala by May 19.
The sheer strength of the flows it manages to pull in will fuel its growth into a depression and probably a minimal cyclone even as it brings flooding rain into Kerala and Tamil Nadu. Later, the system is forecast to travel North-Northeast across South Interior Karnataka, Rayalaseema, Telangana and Coastal Andhra Pradesh before it re-enters the Bay of Bengal off Odisha by May 22.
But the European Centre also points to a progressive weakening of the monsoon flows heading towards the Kerala coast up till May 22 when forecasts are available.
It remains to be seen if the flows will revive thereafter to precipitate the crucial onset over Kerala around the normal date of June 1. Meanwhile, the Met has said that heavy to very heavy rain isolated places of Kerala on Sunday (May 15), a day after the ‘low’ will have taken shape.
By the next day it would become a depression and bring heavy to very heavy rain over Kerala, Coastal Tamil Nadu and South Interior Karnataka.
Heavy to very rain would lash isolated places over Kerala and Tamil Nadu and heavy over isolated places over South Interior Karnataka for a third day on Tuesday.
Parts of North-East India are also expected to slip under a blanket of rainfall during these days, the Met said.
Credits The Hindu Business Line