Weather forecast. N-E monsoon on course to commence from Saturday

ThiruvananthapuramA series of existing and prospective cyclonic circulations over the Bay of Bengal close to Tamil Nadu and Sri Lanka is expected to herald the North-East monsoon over the South Peninsula. India Meteorological Department (IMD) expects the rains to commence from Saturday.

Three circulations in a row

An extended weather outlook from the IMD said an existing circulation over the South-West Bay off the Tamil Nadu coast is less likely to intensify further, but will move westward into Tamil Nadu and Kerala during the weekend and into the early next week. There is a likelihood of forming another cyclonic circulation over the South-West Bay by Sunday/Monday and tracking towards the Tamil Nadu coast. 

Friday noon satellite pictures show clouds (white and green) building over the South-East Bay of Bengal heralding the North-East monsoon as an entire dry land mass (in yellow and red) lies in wait.

This circulation will move across Tamil Nadu and Kerala and emerge later into the South-East and adjoining East-Central Arabian Sea off the Kerala-Karnataka coasts. These two will bring rainfall of varying amounts over Tamil Nadu, Kerala and parts of Karnataka during the ongoing week.

A third circulation may form over the Andaman Sea and adjoining South-East Bay during the subsequent week later part of the week November 3 to 9, though the IMD did not indicate where it is likely headed. 

Strong easterly flows

The enhanced buzz in the Bay is principally because of the strong easterly flows over the neighbouring South China Sea and the adjoining West Pacific. Its cause is further served by the changed track of tropical storm ‘Algae’ off the Philippines (West Pacific) inward to the South China Sea, from being away-going to the open waters of the West Pacific, as lately assessed by global models. 

The tropical storm (depression) is now forecast to track towards the South-East coast of China towards Hong Kong and Hainan Island over the next couple of days, triggering a bank of clouds riding the north-easterly to easterly winds to Indochina and further into the Bay of Bengal. This is seen as setting up cyclonic circulations one after the other over the Bay.  

Wet cover for South Peninsula

The IMD has predicted scattered to fairly widespread light to moderate rainfall with isolated heavy falls, thunderstorms and lightning for Tamil Nadu, Puducherry and Karaikal from Saturday to Tuesday; over Kerala and Mahe on Sunday and Monday; and over Coastal Andhra Pradesh and Yanam on Monday. It will be scattered to fairly widespread light to moderate over the Andaman and Nicobar Islands,  the first land feature the flows encounter as they blow into the Bay during the next seven days.

Rainfall for the subsequent week from Thursday next will likely see scattered to fairly widespread rainfall and isolated heavy falls likely over the Extreme South Peninsular (southern Tamil Nadu and Kerala) during most days of the week. Overall, rainfall activity during the week is likely to be normal to above normal over Extreme South Peninsula and below normal over North-East Tamil Nadu (including Chennai) and adjoining Andhra Pradesh, the extended outlook from the IMD said. 

Rain for North-West India

Of the two western disturbances affecting the hills of North-West India, the first one will hit the region during November 1 to 3 with low intensity. The second one, during November 3 to 5, will be the more productive. The IMD has predicted isolated light rain or snow over the higher ridges of the Himalayas during November 1-3 and scattered to fairly widespread light rain or snow over the mountains and isolated rainfall over the rest and adjoining plains of North-West India from November 3 to 6. IMD said that rains will be normal to above normal over parts of the mountains, near normal over parts of Central and North-West India, and below normal over East and North-East India. 

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