The southwest monsoon is set to climb to a vigorous phase over Kerala during the next three to four days under the combined influence of a low pressure system that has taken shape over the northwest Bay of Bengal and an ideal offshore trough along the west coast.

Heavy-to-very heavy rainfall in some places is the forecast for the State for the next couple of days, with no significant change during the subsequent two days.

The India Meteorological Department (IMD), in its bulletin on Wednesday, predicted very severe weather for the State till Friday, but its numerical weather prediction models, which show the weather possibilities for a seven-day period, showed that the unfolding vigorous spell of downpour could last till June 19.

If the models were to come true, it would mean that the week ahead would require some watching.

Low-lying regions such as Kuttanad may experience flooding, and there are also midland hill tracts vulnerable to landslips.

The Irrigation Department has already started work on cutting open the sandbar separating the sea and the backwaters at Thottappally in Alappuzha district to check flooding in Kuttanad.

This is a precaution taken every year as the monsoon intensifies.

The models on Wednesday showed the low pressure system that had taken shape over the northwest Bay of Bengal taking a track westward across the subcontinent to merge, over the next four days, with the head end of the offshore trough now lying from the Gujarat coast to the Kerala coast.

The monsoon is chugging on a twin engine now, with the low pressure system functioning as one unit spinning the rainclouds over the northwest Bay of Bengal and the offshore trough acting as the other unit causing downpour along the entire stretch of the west coast.

Very intense rainfall is forecast in the areas lying at the head of the offshore trough (Gujarat) by the time the Bay system merges with the weather system on the west coast, while Kerala, which lies at the tail end of the trough, would receive ‘heavy to very heavy rainfall.’

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