Monsoon expected to arrive over Kerala on 31 May: Weather Department

The four-month south-west monsoon season has officially begun. The system is expected to arrive over Kerala on May 31, according to the India Meteorological Department (IMD), with a model error of four days.

In India's mainland, Kerala is the system's first point of entry. The arrival of the monsoon in Kerala is typically on June 1st. In the meantime, the IMD predicted that monsoon flow would appear over the Andaman Sea in a few days and would cover the area close to its usual date of May 20.

Weather Forecast

Over the last six years, IMD has been releasing onset forecasts, and the projections have mostly come true. Last year, the Department predicted that the event will begin on May 30 and end on May 31.

Rainfall during the season was expected to be “most likely” regular this year, at about 98 percent of the long-term average (LPA), with a model error of plus or minus 5%, according to the Department.

As per the IMD, in a note issued along with the forecast made on April 19, the models showed there was a 53 per cent probability that the rainfall will be between 96 per cent and 104 per cent of LPA (normal), a 10 per cent probability that it will be between 104 per cent and 110 per cent of LPA (above normal), and one per cent probability that it will be above 110 per cent of LPA (excess).

On the negative side, there was a 30% chance it was between 90% and 96 percent LPA [below normal] and a 6% chance it was below 90% LPA [deficient].

Next Month Update

However, the forecast is not final.

In June, IMD will update it, taking into account parameters for which data will only be available by then. This is a yearly ritual. The majority of international models tracking El Nino-La Nina have indicated that sea surface temperatures over the equatorial Pacific are warming, among other things.

As a result, La Nina conditions, which could have been beneficial to the monsoon, are weakening, and ENSO conditions are expected by June. Long-term El Nino-La Nina forecasts, on the other hand, are fraught with large uncertainties. The El Nino-La Nina phenomenon could take a different path than predicted.

Ajit Tyagi, director general of the IMD, said the department would keep a close eye on the situation to ensure the country was well prepared in the event of any major changes.

Dipole in the Indian Ocean   

He also stated that the IMD would keep a close eye on developments relating to the Indian Ocean Dipole, which is defined as differences in sea surface temperatures between the eastern and western parts of the Indian Ocean.

International models currently predict that a negative IOD will develop in the monsoon's final stages. As a result, there does not appear to be any chance of a significant impact at this time.

It remains to be seen, however, how it progresses. It is possible that if it develops sooner, it will have a negative impact on the amount of rainfall.