The Hindu Business Line : Brewing `low' in Bay bears watching

Predictions favoured the formation of the next `low' in the Bay of Bengal within the next 24 hours, but stopped short of committing anything on its potency.

While some forecasters expect it not to intensify beyond a point, there are others who say that late-September and early-October systems in the Bay bear watching.

The `low' is an offshoot of a depression (numbered 17W) drifting in from the South China Sea. Perched over Indo-China and Myanmar on Tuesday, it was merely bidding time to emerge over the Bay.

Dr Akhilesh Gupta of the Department of Science and Technology said that there have been occasions when migrant systems have proceeded to become intense storms during this time of the year. "It all boils down to the exact place of genesis and a set of other atmospheric features turning favourable."

Wind shear (inhibiting cyclone genesis) tends to climb down in late September in anticipation of the onset of the northeast monsoon (winter monsoon). This, along with suitable co-ordinates (Head Bay, for one) and readjusting moisture feed, is enough to fire up even innocuous systems to being rampaging storms.

Sea surface temperature (SST) is another major contributor to the building of storms. Bay waters continue to be warm enough to sustain depressions and storms. Across the peninsula, even the Arabian Sea has been known to lob in the occasional cyclone in October, Dr Gupta said.

FRESH STORM

What is interesting to watch is the likely course of a new western Pacific storm, named Xangsane, which is nearing the Philippines. Roaring along a west-northwest trajectory, Xangsane is expected to slide into the South China Sea.

Meanwhile, the resident `low' in east India has shifted to Jharkhand and adjoining north Orissa and Gangetic West Bengal on Tuesday.

It will bring fairly widespread rainfall with isolated heavy falls likely over these regions during the next 24 hours.

The other `low' over northeast and adjoining east central Arabian Sea, remnant of Cyclone Mukda, is likely to weaken further and become unimportant, says a forecast by the National Centre for Medium Range Weather Forecasting (NCMRWF).

RAINS FOR TN

The existing north-south trough over east central Bay is bracing to host the brewing `low'. Under its influence, fairly widespread rainfall is likely over Tamil Nadu and Rayalaseema during the next two days. Rainfall activity may extend later to Karnataka and Kerala as well.

According to Mr Jim Andrews of AccuWeather.com, the trend of the next seven days will be for the Arabian Sea to quiet down. Rains of the southwest monsoon will continue to be a factor, but mostly in Kerala and Karnataka. Excessive but highly localised rains from the Deccan to the far northeast is likely from Wednesday, thanks to the Bay system.

The NCMRWF quoted model predictions to suggest that the southwest monsoon may be readying to withdraw from some more parts of Northwest India.

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