According to the India Meteorological Department (IMD) the southwest monsoon is expected to be delayed by two days and the rains are now likely to hit the Kerala coast on June 3 instead of June 1. In complete divergence, private weather forecasting agency, Skymet said that the southwest monsoon has in fact already arrived over Kerala.
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Skymet, a private weather forecast agency, however, said the monsoon had arrived. This was because two of the three criteria — as defined by the IMD — had been met.
The criteria are- rain-bearing westerlies being at a minimum depth and speed; at least 60% of the available 14 stations in Kerala and coastal Karnataka reporting rainfall of 2.5 mm or more for two consecutive days after May 10; and a certain degree of clouding, indicated by a parameter called ‘outgoing longwave radiation’ (OLR), being below 200 W/square metre.
IMD’s own data indicated that except for the OLR, the other criteria were met. The IMD and Skymet have forecast normal monsoon from June-September this year.
To herald the onset, initial rains first occur over south Andaman Sea and the monsoon winds then advance across the Bay of Bengal. Since 2005, the monsoon has arrived within the error margin of the IMD’s weather models, except in 2015.
