The Hindu Business Line : Mercury rises in northern plains

Passing easterly waves in combination with a periodically accentuating Inter Tropical Convergence Zone (ITCZ) may be spearheading rainfall in the South, but are, by default, pushing up mercury levels in North and Central India.

The anomalous positioning of the seasonal anti-cyclone is allowing the westerlies and southwesterlies to blow into the northern plains, in place of the westerly-to-northwesterly winds, said Mr J.V. Singh of the National Centre for Medium Range Weather Forecasting (NCMRWF).

This would be set right with the expected arrival of a western disturbance from the northwest, which will bring the mercury back to the normal. Currently, they rule above normal by a margin of three to five deg Celsius in North and Central India.

The NCMRWF has forecast the possibility of a formation of an embedded `low' in the easterly waves, which maintain their relentless march over the Bay of Bengal. The T-80 weather model of NCMRWF had picked scent of this event as early as on Monday, Mr Singh said.

The European Centre for Medium-Range Weather Forecasting (ECMWF) also seems to concur with this. The likely date for the event is November 13 (Monday next).

SSTs STILL LOW

Though the ruling sea-surface temperatures in the Bay are less than optimum for sustaining `in situ' (locally borne) systems, the strength and frequency of easterly waves would adequately make up for this shortfall. Embedded troughs in these systems can spin into `low's/depressions, even cyclones.

Mr Jim Andrews of AccuWeather.com says things are still quite unsettled over South India and Sri Lanka. "It strikes me more as an accentuated ITCZ and less of northeast monsoon.

"The big cloud mass over the southeast Arabian Sea looks interesting, although I have seen no numerical forecast model showing any growth of depression or cyclone here," he said.

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