The much-awaited South-West Monsoon has reached the Indian territorial waters. It set in over parts of south Bay of Bengal, Andaman and Nicobar Islands and most parts of the Andaman Sea on Monday.

Announcing this, the India Meteorological Department (IMD) said the conditions were favourable for the further advance of the system over more parts of Bay of Bengal and the remaining parts of the Andaman Sea during the next two days.

The system normally sets in over southeast Bay of Bengal and the south Andaman Sea around May 15 and covers the entire Andaman Sea and the Bay islands around May 20. In other words, the development so far almost follows the textbook style.

However, as for the future, experts are keeping their fingers crossed as a depression has formed over south-east Bay of Bengal and it is expected to intensify further into a cyclonic storm.

The depression lay centred about 920 km east-south east of Chennai on Monday evening. The forecast is that it is likely to intensify gradually into a cyclonic storm and initially move in the north-westerly direction towards Andhra Pradesh coast and subsequently swerve towards Bangladesh or Myanmar.

The experts fear that this could lead to a situation like last year, when severe cyclonic storm “Aila” formed over the Bay of Bengal soon after the monsoon set in over Kerala. While the storm helped in advancing the system over West Bengal and the north-eastern States earlier than normal dates, it subsequently led to a weakening of the cross equatorial flow and thereby the monsoon system.

It took a week for the monsoon to revive, but the revival was not too strong. It petered off in a few days and the system once again went into a break phase and remained in that state for 12 full days.

Consequently, the country-wide rainfall recorded in June last one of the lowest, at a mere 53 per cent of the long period average (LPA) for the month. Though subsequently things improved, the deficit could never be bridged, resulting in the season ending with an overall deficit of 22 per cent.

IMD Director-General Ajit Tyagi, however, expressed the hope that things would be different this year. Pointing out that no two situations need be similar, he expressed optimism that the cyclonic storm that was in the making may help in the strengthening of the Arabian Sea arm of the monsoon system instead of being a dampener.

In its long range forecast issued last month for the season as a whole, the IMD predicted that the season-wide rainfall this year for the country in its entirety was likely to be normal at 98 per cent of the LPA, with a model error of plus or minus 5 per cent. The IMD has recently forecast that the monsoon was likely to set in over Kerala on May 30 with a model error of plus or minus four days.

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