First 10 days of October deliver 13 per cent excess rain over country

As moderate to heavy rain continues to lash parts of Peninsular India and the South Peninsula, a heightened state of activity in the upstream West Pacific/South China Sea promises to keep the Bay of Bengal active and, by extension, prospects of the North-East monsoon.

The first 10 days of October have already brought excess rainfall of 13 per cent to the country as a whole with States such as Kerala — which had to contend with a deficit during the preceding South-West monsoon — making smart gains (excess of 71 per cent) so far, even before the North-East monsoon has formally set in.

Excess rain until Oct 10

In the core North-East monsoon command area, only Coastal Andhra Pradesh (-53 per cent) Telangana (-35 per cent) are in deficit. In Central India, only Vidarbha (-22 per cent) and East Gujarat (-29 per cent) are in some deficit and in North-West India, Himachal Pradesh (-25 per cent) and West Uttar Pradesh (-33 per cent). In the East and North-East, a bulk of the deficit is in the plains of West Bengal (-46 per cent) and Arunachal Pradesh (-6 per cent).

Two more rain systems brewing in the Bay

For the present, a remnant tropical depression from erstwhile tropical storm ‘Lionrock’ in the South China Sea is in the process of navigating Indochina before it can drop anchor into the Bay and set up a low-pressure area. The India Meteorological Department (IMD) has been on the lookout for the ‘low’ over the past few days, which has evaded it pending the arrival of the remnant depression.

Circulation over North Andaman Sea

The IMD has continued to monitor a potent cyclonic circulation over the North Andaman Sea, which will be the foundation over which the impending ‘low’ will be built by Tuesday evening, it said in its updated outlook on Monday. It is likely to become ‘more marked’ (intensify) and move towards the South Odisha-North Andhra Pradesh coasts during subsequent 4-5 days.

Isolated thunderstorms (wind speed of 40-50 km/hr gusting to 60 km/hr) and heavy to very heavy falls have been forecast over the Andaman & Nicobar Islands during the next five days.

Arabian Sea circulation

To the other side of the peninsula, a cyclonic circulation has persisted over the East-Central Arabian Sea for the past few days as if lying in wait for the Bay to signal the arrival of the ‘low’ likely followed by that of the North-East monsoon. The Arabian Sea system has already thrown down a trough linking it with the circulation over the North Andaman Sea, and is expected to hang in there for another three to four days.

Rains to scale up over Kerala, Tamil Nadu as MJO wave arrives

The IMD has forecast fairly widespread to widespread light to moderate rain with isolated heavy falls over the South Peninsula for five more days and over Maharashtra for two days. Isolated very heavy rainfall is likely over Kerala and Mahe from tomorrow (Tuesday) to Thursday.

An extended outlook valid for October 16 to 18 said that scattered to fairly widespread rainfall with isolated heavy falls is likely over the Islands, Karnataka, Kerala and Tamil Nadu. Scattered to fairly widespread light/moderate rainfall is likely over North-East, East and Central India and East Uttar Pradesh and isolated over West Uttar Pradesh and Uttarakhand.

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