Wednesday, May 27, 2009

Severe cyclone ‘Aila’ crosses West Bengal coast - IMD

Sunday's deep depression in the Bay of Bengal basin intensified two rounds to become severe cyclone Aila which crossed the West Bengal coast on Monday afternoon.

The system was later traced to Gangetic West Bengal close to Diamond Harbour, and is expected to keep moving north weakening gradually in the process.

'Aila' set off gale-force winds and triggered torrential rainfall while hitting the home stretch causing loss of life and severe damage to property.

The landfall also heralded the onset of southwest monsoon over north-east India. The northern limit of monsoon was heaved as a whole to the north in the process.

The northward movement of monsoon had been tied with the fortunes of 'Aila' that posed a while before making the last-mile run towards Kolkata.

'Aila's picking up system strength and speed in lateral movement meant that the northern limit of monsoon would also get yanked to the north.

HEAVY FALLS

India Meteorological Department (IMD) said the northern limit aligned itself along Mangalore, Dharmapuri, Chennai, Paradip, Balasore, Bankura and Gangtok on Monday after the cross-over.

The monsoon has thus advanced further into north Kerala, parts of coastal Karnataka and south interior Karnataka and parts of Tamil Nadu. The IMD has warned of heavy to very heavy falls at a few places and isolated extremely heavy falls (above 25 cm) over Gangetic West Bengal and north coastal Orissa over the next two days.

Isolated heavy to very heavy rainfall is likely over the north-eastern States, Bihar, Jharkhand, Kerala, Andaman and Nicobar Islands and Lakshadweep.

Forecast said that rain or thundershowers are likely at most places over Kerala and Lakshadweep, many places over coastal and south interior Karnataka and at a few places over coastal Andhra Pradesh and north interior Karnataka.

RENEWED MJO

International weather models continued to suggest renewed but a comparably weaker but rain-friendly Madden-Julian Oscillation wave activity over south Arabian Sea and adjoining equatorial Indian Ocean around June 5.

This would have a rub-off effect on the circulatory pattern in the peninsular seas also as evidenced in multiple model forecast for re-convergence of the flows and revival of rains over the southwest coast.

In the first instance, residual convection available in the southwest and adjoining southeast Bay of Bengal is shown to accentuate and burst out in rains south of Myanmar. The European Centre for Medium-Range Weather Forecasts tends to posit the activity over central Bay and later along the Andhra Pradesh coast.

As for the Arabian Sea, the Climate Prediction Centre (CPC) of the US National Weather Services sees cross-equatorial flows strengthening off the Horn of Africa and throwing up a 'low' over extreme west Arabian Sea.

It is later predicted to move east-northeast towards India's west coast but weakening in the process. It is ultimately shown to drift into the Mumbai-south Gujarat coast around June 8 even as rains build along the coast from south.

This could possibly herald the arrival of monsoon into the Konkan-Mumbai belt slightly ahead of schedule. The Roundy-Albany model for 'cyclogenesis' (birth of cyclone systems) also has pointed towards a flare-up along the Mumbai-south Gujarat region around this time.

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