The normal onset date of monsoon over Kerala is June 1st. We have already crossed the onset date. Pre-monsoon rains have already started over Kerala, interior Tamil Nadu, and South Karnataka. Rain activities over Kerala may intensify further marking the onset of monsoon in the next 2 to 3 days.
Monsoon onset will not have a thumping start over Kerala. The reason being a low-pressure area is likely to form over Southeast Arabian Sea around June 6 or 7. This low-pressure area will move in North Northwest direction and will gradually intensify into a depression. The weather system over the Arabian Sea will restrict the flow of south-westerly winds over the Indian mainland. These south-westerly winds are responsible for the further progress of monsoon over the interior Peninsula.
Light to moderate rain with one or two intense spells may occur over Kerala during the next 4 to 5 days. However, heavy to very heavy downpours will remain absent. Moisture will be pulled away by the depression therefore, despite the onset of monsoon rain activities will be scanty over the interior Peninsula such as Karnataka, Tamil Nadu, and Rayalaseema.
On the other hand, the eastern arm of the monsoon will progress over Northeast India in the wake of a low-pressure area over the Southeast Bay of Bengal near the Myanmar coast. This low-pressure area will move in a Northerly direction and will intensify rainfall over the northeastern parts of the country.