Wednesday, June 02, 2010

Cyclone Phet seen soaking arid north-west by weekend

The deep depression over west-central and adjoining east-central Arabian Sea remained practically stationary overnight on Tuesday but intensified faster than anticipated into a cyclonic storm, named ‘Phet.'
Tropical Cyclone Phet lay centred about 1,100 km west-southwest of Mumbai, 1,030 km southwest of Naliya (Kutch) and 1,100 km south-southwest of Karachi.


An India Meteorological Department (IMD) update said that ‘Phet' would intensify further into a severe cyclonic storm and move slowly in a north-northwesterly to northerly direction for the next 24 hours.
It is forecast to re-curve under the influence of opposing flows from an approaching westerly trough (associated with western disturbances over northwest India) and guided northeast to cross Gujarat and adjoining Pakistan coast.
According to the US Navy's Joint Typhoon Warning Centre, ‘Phet' has been able to ramp up faster than anticipated thanks to further maturing of the enabling environment overnight on Tuesday.
The ‘window effect' on top got further fine-tuned allowing the system even more free, and the vertical wind shear (sudden change in wind speed and direction with height) values also tumbled a couple of notches.
Wind shear of up to 25 knots is considered moderate, but anything above that could cap the height — and therefore strength — of a storm and even kill it.


The London-based Tropical Storm Risk Group said that Karachi and Shahbandar in Pakistan; and Jakhar, Mandvi, Sonmiani, Morbi and Jamnagar in Gujarat could be brought under the fury of the storm of category-2 strength on the Saffir-Simpson scale of intensity.
The European Centre for Medium-Range Weather Forecasts (ECMWF) shows ‘Phet' settling into a perch over north Gujarat and adjoining south-west Rajasthan 24 hours into landfall on Friday/Saturday but without losing much intensity.
But Dr Akhilesh Gupta, leading operational forecaster and Adviser to the Department of Science and Technology, says that it may not be the case for a variety of reasons.
For one, after landfall, the westerly trough may lop off the ‘head' of the towering cyclone as wind shear values rise. For another, the arid surface of Gujarat and Rajasthan affords little by way of moisture feed, the life-blood of a cyclonic storm, undermining the base of the system as well.
But the ‘lopped head' of the storm is tipped to roll over northwest India, unleashing heavy to very heavy rains but tapering off in strength as it turns over and over further inland.


The rains would thus extend from Gujarat, into southwest and southeast Rajasthan, adjoining Haryana, Delhi and even Punjab.
From here, the westerlies might take the remnant ‘Phet' circulation to over Uttar Pradesh and Bihar.
According to Dr Gupta, it is possible that the wet session triggered by ‘Phet' might last for two days from the day of landfall.
The rains would be a boon for the non-irrigated farm lands that ‘Phet' chooses to rain it down on, though sowing operations for the kharif crop are at least 15 days away.
The welcome precipitation would help boost the soil moisture appreciably, Dr Gupta told Business Line.
It may not, however, make for much difference to farmers in Punjab and Haryana who carry out transplanting operations under controlled conditions (on irrigated land).
The most redeeming aspect about cyclone ‘Phet' is that associated cloudiness and rains would bring some badly needed relief to the scorching heat in the northwest.
The IMD has said that fairly widespread rainfall with isolated heavy to very heavy falls would commence over coastal areas of Gujarat from Thursday and increase thereafter.
Squally winds with speed reaching 55 to 65 km/hr gusting to 75 km/hr would commence along and off Gujarat coast from Wednesday and increase gradually.
Sea condition will be very rough along and off Gujarat coast and fishermen are advised not venture into the sea.

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