In the run-up to the keenly awaited North-East monsoon (NEM), India Meteorological Department (IMD) is closely monitoring a cyclonic circulation lying over North Andaman Sea. The system is expected to move nearly westwards (towards the Tamil Nadu-Andhra Pradesh coast) during the next 3-4 days.

The IMD has not indicated either the expected level of intensification or a likely point of landfall. Sea-surface temperatures in South Bay of Bengal are just above the threshold to support system growth but warmer towards Central Bay and further northward, which is ideal for intensification. These, along with any incoming western disturbance over North-West India moving eastward, could potentially determine the system movement.

IMD outlook awaited

The IMD is expected to come out with its outlook for NEM soon. Currently, it is watching the withdrawal line of the preceding South-West monsoon, which has stalled over the past week. On Wednesday, M Rajeevan (@rajeevan61), acclaimed monsoon expert and former Secretary of the Ministry of Earth Sciences, tweeted: ‘Monsoon Update: South-West monsoon will now quickly withdraw from the country in next 7-10 days. Then focus should be on the North-East monsoon and cyclones. Early indications suggest conditions are becoming favourable for onset of NEM by October 20.’ Rajeevan has tagged both the IMD (@Indiametdept) and the ministry (@moesgoi) in the tweet.

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The skies over north-west India cleared by Tuesday evening though heavy thunderstorms were parked over west Maharashtra (including Mumbai), east India and parts of north interior Karnataka. The south-west monsoon is expected to resume withdrawal from the North-West in next 4-5 days.

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Reference to cyclones

The reference in Rajeevan’s to “cyclones” may not be entirely out of context given that both the monsoon transition period from South-West to North-East and the North-East monsoon itself is known to host strong weather systems in the Bay. Some weather models have hinted at the possibility of Wednesday’s cyclonic circulation over the North Andaman Sea progressively gaining traction and growing in strength into the next week. Meanwhile, the IMD has predicted fairly widespread to widespread light to moderate rainfall with isolated heavy falls, thunderstorms and lightning over Tamil Nadu, Puducherry, and Rayalaseema for the next four days; over South Interior Karnataka on Wednesday, Saturday and Sunday; Coastal Andhra Pradesh, on Thursday and Friday; and Kerala and Mahe Saturday and Sunday.

Weather trackers on cue

Weather aficionado @Selwyyyn tweeted that the circulation over the North Andaman Sea likely to get embedded inside an East-West trough (over the Bay) and move westward towards North Tamil Nadu-South Andhra Pradesh coasts. It is likely to cause widespread rains from Friday to Monday next. Separately, two other Twitter handles were cautiously optimistic over the fluctuating fortunes over the Bay.

@jhrishi2 said ‘as we gradually enter the NEM season, lots of noise from model outputs already signalling a potential system around October third week. As always, n number of factors will play a significant role for such systems which is definitely way too early to talk about.’ @caregroupjoseph said lots of twists and turns to come to a conclusion on possible onset date. Possible onset windows are October 19-22 and October 29-November 2 (more likelier of the two). @chennai13621472 too expected the onset in two different windows of October 21-28 and October 28-November 4.