A low-pressure area currently forming over central Bay of Bengal is seen to be interfering with the forward advance of the monsoon, with the potential to neutralise the gains from its early arrival.

Weather scientists say this low-pressure area —expected to develop fully around May 23 — would initially help in bringing rain to north-eastern India and parts of West Bengal within days of the monsoon hitting Kerala. However, it would also suck in monsoon winds and prevent their smooth advance into the peninsula.

The monsoon has already arrived in some of the Andaman and Nicobar Islands, where it rained on Tuesday. The Indian Meteorological Department (IMD), which had correctly forecast the arrival of the rains in the islands, said on Thursday that conditions were now becoming favourable for the onset of the monsoon in Kerala over the next couple of days. It will probably start raining this Sunday, weather scientists said, at least a week ahead of June 1, the monsoon’s normal date of arrival.

The low-pressure area over the Bay of Bengal will, however, lead to the weakening of the monsoon system; as a result, Karnataka, Maharashtra and peninsular India are unlikely to get too much rain.

The silver lining in this scenario, however, is the Madden Julian Oscillation (MJO), a wind anomaly in the equatorial region, which helps in triggering the monsoon. The Climate Prediction Centre in the US has been forecasting a stagnation of MJO over the Indian sub-continent, a departure from the usual, for a prolonged period.

The MJO, which generally remains over the Indian region for only 4-5 days, is likely to hold on till the first week of June, which could help in the revival of the monsoon.

Scientists said if the monsoon did not revive by the first week of next month, it could cause serious concern. The monsoon generally spreads to most parts of peninsular India within 10-12 days of hitting Kerala. The sowing of paddy in these regions takes place around June 10. If the monsoon fails to revive in the first week of June, the sowing could be delayed.

The monsoon’s advance was disrupted last year by cyclone Golu in the Arabian Sea. Only after a revival happens in the first week of June will the country see sustained rainfall, scientists said.