The Hindu Business Line : Rogue whirl seen rearing head in Arabian Sea

Thiruvananthapuram, May 18 The European Centre for Medium-Range Weather Forecasts (ECMWF) sees a rogue circulation spin up in the west-central Arabian Sea about the same time as the westerly winds are predicted to accelerate in the run up to monsoon.

The circulation is shown to move in a west-northwest direction, away from the Indian coast, during the two days from May 27 for which forecasts are available. This is more or less the track pursued by super cyclone Gonu during last year, disrupting monsoon flows in the onset phase.

DIFFERING VIEW

But the US National Centres for Environmental Prediction (NCEP) begs to differ, and goes on to posit a cyclonic whirl in the Lakshadweep region around May 24. This would act as the final check post for incoming monsoon flows as they brace to hit the Kerala coast.

NCEP sees the westerlies blowing into Sri Lankan coast two days from now, leading up to the onset of the seasonal rains in due course. The onset over Kerala should normally follow within a week’s time.

The Fleet Numerical Meteorology and Oceanography Centre (FNMOC) of US Navy is more or less in agreement with this outlook, and predicts a wave of rains reaching the Sri Lanka and Kerala coasts within the next few days. But the Bay of Bengal is shown to be in a dormant state right through this period.

The first hint of activity in the Bay that the ECMWF is able to perceive is around May 28, coinciding with the strengthening of the westerly flows. But this ‘low’ would not be able to penetrate the southeast coast since the seasonal trough (monsoon trough over land) would not be in place by that time.

‘HEAT LOW’

On Sunday, the ‘heat low’ that anchors the monsoon trough in the northwest was well-organised over west Rajasthan. But the thunderstorms and squalls have cooled down the atmosphere and prevented the foot print of this ‘heat trough’ from being expanded to the east-southeast.

An India Meteorological Department (IMD) update said on Sunday that scattered rain or thundershowers accompanied with isolated thunder squalls are likely over the Indo-Gangetic plains for three days from Monday. The maximum temperatures are likely to drop during the same period.

A north-south trough is likely to cause fairly widespread rainfall with isolated heavy falls over the Northeastern States during the next four days. Scattered rain or thundershowers with isolated thunder squalls are also likely over West Bengal and Sikkim.

The prevailing heat wave conditions over some parts of coastal Andhra Pradesh are likely to abate during the next two days. On Sunday, the highest maximum temperature of 45.9{ring}C was recorded at Kakinada.

PHILIPPNES TYPHOON

Meanwhile, Philippines saw Tropical Storm Halong take birth in the South China Sea and cross the archipelago only to race up to typhoon strength in the West Pacific. It has since weakened, and according to ECMWF, would be the last in the series to be yanked off to the north-northeast by a passing westerly system.

In fact, the West Pacific is forecast to throw up another ‘low’ around May 27 and this would head west-northwest in the opposite direction, which is a helpful for the Indian monsoon. The system is seen crossing Philippines and getting strengthened in the South China Sea by May 28.

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