NEW DELHI: The India Meteorological Department (IMD) on Wednesday said the monsoon was not likely to set in over Kerala before May 27, contrary to its earlier forecast that it could set in on May 24, with a model error of plus or minus three days.

Kerala is the first point of entry of monsoon into the country.

Explaining why the forecast went wrong, the agency said the onset was not likely for the next three or four days as the monsoon flow was yet to get re-organised fully after having been disrupted by the cyclonic storm, which crossed the Bangladesh coast on May 15.

Equatorial flow

"The monsoon is slowly organising itself back after the disruption. During the last few days, a weak cross equatorial flow has established over the Arabian Sea, with associated thin clouds. However, it is strengthening and progress towards the west coast has been inhibited due to development of an anomalous low-level circulation over west-central Arabian Sea and persistence of a mid-latitude westerly trough over the Indian region."

The agency also emphasised that monsoon was a planetary scale system and exhibited sporadic variations. The department was monitoring its progress and updates would be issued regularly.

Sets in over Andaman Sea

The monsoon had set in over the Andaman Sea and south-east Bay of Bengal on May 10, about a week earlier than normal for that region, and the earlier forecast (made on May 14) was based on a statistical model and its predictors favoured an early onset over Kerala, it said.

The IMD had been issuing forecast for the monsoon onset over Kerala for the past three years.

In 2005, the onset was well within the model error of plus or minus three days — the forecast was for the onset on June 7, whereas the system actually set in on June 5. Last year, the forecast was for May 30 and the actual onset occurred on May 26, four days earlier.

During the last 50 years, the earliest onset over Kerala was in 1960, when the system set in on May 14, and the most delayed onset was in 1972 when the monsoon arrived on June 18.

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