Friday, October 30, 2009

North-East monsoon sets in over coastal TN (Issued on 29-Oct-09)

The north-east monsoon has set in over coastal Tamil Nadu and the larger peninsular India at least a week late than normal, India Meteorological Department (IMD) announced on Thursday.

The north-east monsoon has been active over coastal Tamil Nadu during the 24 hours ending Thursday morning, according to an update from the Chennai Met Centre.

Strong northeasterly to easterlies currently prevail over peninsular India. An almost contiguous pair of troughs of lower pressure (not amounting to a `lowpressure' area) over southwest Bay of Bengal off south Tamil Nadu and Sri Lanka coasts and southeast Bay of Bengal and neighbourhood is driving the winds.

TO FURTHER STRENGHEN

Guidance from the numerical weather products indicated further strengthening of easterly and northeasterly winds.

Satellite imagery on Thursday showed convective clouds over parts of south Andaman Sea, southwest Bay of Bengal and southeast Arabian Sea. An IMD outlook valid until October 31 indicated the possibility of scattered to fairly widespread rainfall over south peninsular India during the next three days.

Meanwhile, true to forecasts, a new typhoon, named Mirinae, is currently stalking the west Pacific waters. Classified as Category-2 on the Saffir-Simpson scale of storm intensity (154 to 177 km/hr), Mirinae is approaching the storm-battered Philippines for a landfall by late night on Friday.

The London-based Tropical Storm Risk Group, as do most storm tracking models, indicate that Mirinae would slid into the South China Sea, retain typhoon status, and head straight west for a second landfall over Vietnam/ Thailand around November 2/3.

Here, the system is likely to face a barrage of opposing westerlies associated with a westerly trough dipping low over mainland India and heading further eastward.

Mirinae is seen not making much headway either with its onward push across Indo-China into the adjoining Bay of Bengal. Instead, the European Centre for Medium-Range Weather Forecasts (ECMWF) predicts a `ripple effect' being generated over downstream southwest Arabian Sea in the form of a low-pressure area.

STRONG MONSOON

Predictions for the week from October 29 (Thursday) to November 5 by the US National Centres for Environmental Prediction (NCEP) favoured the possibility of strong northeast monsoon activity along the Tamil Nadu coast, the southern peninsular tip, parts of the Kerala coast and Sri Lanka.

The following week (November 6 to 14) is likely to witness a blow-up in accumulated rainfall over the southeast Tamil Nadu coast, west and northwest Sri Lanka, the Palk Straits and the peninsular tip.

Meanwhile, cyclone phase evaluation modelling by three major players - the NGP model of the US Navy, Global Forecasting System by the NCEP and the Canadian Meteorological Centre - indicated the formation of a weather system to the southeast of Sri Lanka around Friday.

It is forecast to track west or west-northwest into equatorial Indian Ocean and adjoining southwest Arabian Sea. This could ultimately set up the `low' over southwest Arabian Sea as has been forecast by the ECMWF.

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