A cyclonic circulation over the South-East Arabian Sea and its projected northward movement have prompted India Meteorological Department (IMD) to defer a call on prospects of the monsoon onset over Kerala a day after the original window of June 4 (with a margin of plus or minus four days) for the event opened, on Monday.
Westerly winds flag
The IMD said on Monday the column of westerly winds over the South Arabian Sea on the monsoon highway to Kerala has risen only to 2.1 km into the atmosphere, which is about a third of the required height.
The location of the cyclonic circulation is too at a disadvantage, which has caused the clouds to concentrate quite some distance away from the Kerala coast.
This circulation may deepen into a low-pressure area, further marshalling the monsoon flows around, and may grow into strength as a depression by Friday over the South-East and adjoining East-Central Arabian Sea, away from the Kerala and Karnataka coasts.
Associated clouds may linger around the system, likely ruling out an onset over the coast for at least until Friday.
Being closely monitored
In view of “the formation and intensification of this system and its near northward movement which may critically influence the advance of the monsoon, the IMD is closely monitoring the situation…and will issue daily updates,” a statement from the national forecaster said on Monday.
A look at the latest satellite pictures also clearly how the monsoon onset is being delayed over Kerala.
Delayed along the way
The monsoon called in along the way at major pit-stops including Myanmar, the Andaman & Nicobar Islands, and Sri Lanka by an order of up to 10 days.
Weather watchers had expressed fears this delay could get carried into the onset dynamics over Kerala, which seem to be proving now. The unpredictable cyclonic circulation/depression has added to the overall uncertainty.
At noon on Monday, prevailing winds were weak north-westerlies along the coast. They need to be westerly to south-westerly and fill the column up to the required height for the onset.
This may not happen until June 9-10 (Friday/Saturday), as per IMD’s numerical model projections based on the expected lateral movement of the depression. Most global models agree on this.