May 28 Weather conditions seem to have reverted to pre-monsoon coordinates with a signature north-south trough (or wind discontinuity) reappearing along 'the trunk' of mainland India.
The northern limit of monsoon as on Monday passed through Mangalore, Dharmapuri, Chennai, Paradip, Balasore, Bankura and Gangtok. No further progress has been made ever since.
UNSTABLE WEATHER
Opposing wind streams from the northwest and the southeast of the peninsula merge along the formation and cause instability. The IMD has forecast rain or thundershowers in the region over the next three days.
Residual moisture from erstwhile cyclone Aila is available over east and northeast of the country. Rain or thundershowers are possible at a few places over the Indo-Gangetic plains until Sunday. This would also bring down maximum temperatures by 2-4 deg Celsius over the region.
ANDAMAN RAINS
Meanwhile, isolated heavy rainfall has been warned of over Andaman and Nicobar Islands during the next two days. The Canadian Meteorological Centre saw a circulation spinning up here and heading north-northeast to drive rains into southern Myanmar by Sunday.
The Thailand Met Department observed that 'rather strong' monsoon prevailed over the Andaman Sea and the Thai Gulf on Thursday. Torrential rainfall has been warned of in the region with isolated heavy spells. Ships have been advised to proceed with cation until Sunday. A 24-hour forecast spoke of 'very cloudy' conditions with fairly widespread thundershowers and isolated heavy rain. Southwesterly winds may reach speeds of up to 35 km/hr. Fresh activity would be triggered in the Arabian Sea also during the next three days, an IMD outlook said.
PACIFIC CYCLONE
The Climate Prediction Centre (CPC) of the US National Weather Services said enhanced rainfall is likely over the Arabian Sea, southern India to Southeast Asia during the week ending June 1.
It attributed this to the prevailing Indian and Southeast Asian monsoon, above-normal sea-surface temperatures in some areas and interaction with an extra-tropical circulation (westerly system to the north of Himalayas but mainly impacting south-east Asia).
In what is being seen as prejudicial to monsoon over mainland India, the CPC sees the threat of tropical cyclone development for parts of South China Sea (just east of the Bay of Bengal) and adjoining west Pacific.
A tropical cyclone spinning up could do to the monsoon what Tropical Cyclone Aila has already managed to disrupt wind flows and appropriate incoming moisture to itself.
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