Normal to slightly below normal N-E monsoon, say global models

Extended forecast put out by India Met Department (IMD) has said that overall rainfall activity is likely to be above normal over most parts of Peninsular India during the first week ending October 3.

The second week from October 4 to 10 is likely to see normal to above normal rain over Tamil Nadu, Kerala, Coastal Karnataka, and parts of Maharashtra as the countdown begins for the North-East monsoon.

Cyclogenesis chances

Importantly, the IMD did not see cyclogenesis (birth of low-pressure areas/depression) during the first week. But, deviating from the routine, it did not comment anything about the possibility during the second week.

A couple of global weather models have been hinting at such possibility exactly during the second week beginning October 4. In fact, the US National Weather Services put both the Arabian Sea and the Bay of Bengal under watch on Friday.

Meanwhile, global model forecasts indicated normal to just below normal rainfall during October-November-December after the South-West monsoon officially draws to a close by Sunday (September 30).

BusinessLine reviewed forecasts put out by the UK Met Office; Busan, South Korea-based Asia-Pacific Climate Centre; the Application Labaratory of Japanese forecaster Jamstec; and International Research Institute (IRI) at Columbia University.

Of these, the IRI saw southern parts of Tamil Nadu in rain deficit during October-November-December while it is shown as growing bigger in November-December-January.

‘optimistic’ outlook

The other surveyed were more optimistic about the scenario; in fact, none saw major deficits cropping anywhere in the three southern states except in December. The IMD’s official forecast for the season is awaited.

Meanwhile, Friday saw thunderstorms lash Madhya Maharashtra, Interior Karnataka, Rayalaseema, Tamil Nadu, Kerala, plains of Bengal, and Sikkim until afternoon as the unstable weather associated with monsoon transition became entrenched.

The 24 hours ending in the morning saw very heavy rain break out over Tamil Nadu while being heavy over South Interior Karnataka. Fairly widespread to widespread rain with heavy rain is forecast for Karnataka, Kerala and Tamil Nadu until Sunday.

In the North, conditions are favourable for commencement of withdrawal of the monsoon from parts of West Rajasthan during the next two days. The seasonal anticyclone that repels the monsoon winds is in the process of establishing over the region.

With two days to go, the South-West monsoon has run up a deficit of nine per cent with hardly any sign of major recovery. August recorded a deficit of eight per cent; July six per cent; and June, five per cent. September deficit could be much higher.

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