Fairly widespread rainfall with isolated heavy rainfall over Nicobar Islands on Monday morning, set to continue into Tuesday, may set up favourable conditions for advance of south-west monsoon into parts of Andaman Sea, south Bay of Bengal and Andaman and Nicobar Islands, India Meteorological Department (IMD) has said.

It expects rains over Nicobar Islands to become widespread with isolated heavy to very heavy falls into Tuesday. Wind speeds projected in numerical model predications indicate monsoon may hit south-east Arabian Sea and Kerala anytime after May 20. 

Making rapid strides

The IMD expects to see the monsoon making rapid strides to advance in near synchronic fashion to enter south Arabian Sea, Maldives and Comorin; more parts of south Bay; entire Andaman and Nicobar Islands and Andaman Sea; and central Bay. 

It is not usual for a mention about Arabian Sea side (south Arabian Sea, Maldives and Comorin area) to come so early into the season when monsoon has not even checked into the Bay. But robust build-up, as the winds turn across the equator from east of African coast to become south-westerly across Indian Ocean, appear to have emboldened IMD to to take the call. 

Pre-monsoon sizzles

This also coincides with an expansive phase of pre-monsoon weather at many places over land, alternated by severe heat during day followed in evening by fierce thunderstorms, isolated heavy rainfall, lightning, hailstorms and dust storms. Even more rough weather is forecast this week, especially for South Peninsula and East and Central India. 

Myanmar onset reset

Monsoon may hit Myanmar anytime after its national forecaster advanced onset window for southern parts of the country between May 12 and 14, after reassessing the vigour with which the seasonal weather system is advancing into South Asia. 

Earlier, Myanmar had said it expected monsoon to hit its south between May 16 and 20 against the normal date of May 18. This is now being advanced by almost a week in line with normal pattern that envisions an onset ahead of south-east Bay. 

Hints ‘low’ may form

Myanmar has also said a low-pressure area may form over the Andaman Sea and south Bay, which may further intensify into a depression during next 10 days. This fails to find consensus with global models, though it is likely an elongated trough or a helpful circulation may form, likely propagating towards West Bengal/Bangladesh coasts. 

Sri Lanka rains

After Myanmar and south-east Bay/south Andaman Sea, monsoon arrives over Sri Lanka, before unfolding along Kerala coast. Sri Lankan Meteorological Department website is currently facing technical issues, but said in a forecast its north-western and southern provinces may witness ‘showery conditions’ backed by ‘fairly strong’ winds at 30-40 km/hr in speed. 

Winds over Maldives

While this is adequate to precipitate monsoon, Sri Lankan Met has warned winds they can escalate to 50-55 km/hr at times over sea off the coast extending from Chilaw to Kankasanthurai via Mannar and from Galle to Pottuvil via Hambantota. Maldives, which lies to its south-west, was reporting wind speeds of 20 to 37 km/hr with gusts of 64 km/hr. 

Published on May 12, 2025