The Climate Prediction Centre of the US National Weather Services has put the Bay of Bengal under cyclone watch during October 7-12 due to what looks like an extension of linearly progressive turbulent weather from the South China Sea/West Pacific.
The peninsular seas are known to harbour cyclones during this phase in line with monsoon withdrawal and fading “wind shear” in the upper levels of the atmosphere. Wind shear caps cyclone development by lopping off its top. Some weather models had tossed up the possibility of a building system in the Arabian Sea as the prevailing well-marked low from the Bay of Bengal tracked to the west before sliding in there.
This is now being ruled out and models suggest that the low may be subsumed by an approaching westerly trough dipping into the Arabian Sea by Sunday.
Thereafter, the system would be heaved across to head north-northeast over central and northwest India to bring non-seasonal rains to these regions until October 9.
The India Met Department (IMD), too, has forecast scattered to fairly widespread rainfall over the Indo-Gangetic plains, central and adjoining peninsular India from Monday to Wednesday. Meanwhile, the west Pacific is hosting two Category-4 typhoons of destructive strength close on the heels of typhoon Ketsana making a landfall downstream over Vietnam two days ago.
Of the two, Parma is nearing a landfall over northern Luzon, where hundreds have already perished after Ketsana ploughed the archipelago as a tropical storm, several notches below typhoon status.
CATEGORY-5 STORM
The London-based Tropical Storm Risk Group indicated that Parma may emerge into South China Sea and could undergo another round of intensification. The other prevailing Category-4 storm is Melor, but the Philippines would be spared thanks to the intervention of a westerly trough (extension of the same trough approaching northwest India).
The prolonged stay over the warm Pacific waters would give the kick for Melor to ramp up into a category-topping rank 5 on the Saffir-Simpson scale for typhoon intensity.
The westerly trough is shown to appropriate Melor (nearly mimicking the activity over India) making it to re-curve to the north-northeast and head for the Japan coast early next week.
The turbulence in the massive trough extending from India right into the west Pacific is forecast to continue with models showing further development of weather systems in the west Pacific/South China Sea.
Meanwhile, the IMD said in an update on Friday that the previous day’s well marked low has at last started moving west, crossed into land. It has since lain over Telangana and neighbourhood. Fairly widespread rainfall with isolated heavy to very heavy falls has been forecast over Orissa and Andhra Pradesh during the next 24 hours.
Fairly widespread rainfall with isolated heavy to very heavy falls is also likely over Maharashtra, Goa, Karnataka, Kerala, Lakshadweep and Andaman and Nicobar Islands during the next three days.
Satellite pictures showed convective clouds over central and parts of southwest Bay of Bengal, Andaman Sea, Andhra Pradesh, coastal Orissa, south Maharashtra, Karnataka and east-central and southeast Arabian Sea.
The Regional Met Centre, Chennai, said in its update that the monsoon has been vigorous over Kerala, Rayalaseema, Telangana and north interior Karnataka and active over coastal Andhra Pradesh and coastal Karnataka during the 24 hours ending Friday morning.
Rainfall occurred at most places over Kerala, Telangana, Lakshadweep, coastal and north interior Karnataka; and at many places over coastal Andhra Pradesh, Rayalaseema and south interior Karnataka.
Forecast for the next two days said that rain or thundershowers are likely at most places over Karnataka, Rayalaseema, south coastal Andhra Pradesh; at many places over Telangana, Kerala, Lakshadweep and north coastal Andhra Pradesh and at a few places over Tamil Nadu and Puducherry.
A warning valid for the next two days said that scattered heavy to isolated very heavy rain is likely over south coastal Andhra Pradesh, Rayalaseema, Kerala and Karnataka during the next two days.
Isolated heavy rain is also likely to occur over north coastal Andhra Pradesh, Telangana and Lakshadweep during the same period.
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