MONSOON TAIL

A super-drencher upper air cyclonic circulation persisting over North-East Rajasthan still has what it takes to coerce seasonal westerlies scoop up moisture from far-off Bay of Bengal and dump it over North-West India.

An itinerant western disturbance has been interacting with monsoon easterlies spawned by a low-pressure area and originating from the Bay over the past few days.

HEAVY RAIN ALERT

The India Meteorological Department (IMD) has warned of the possibility of isolated heavy rainfall over Himachal Pradesh, Uttarkhand, Punjab, Haryana, Chandigarh, Delhi, North Rajasthan and West Uttar Pradesh for at least two more days.

The last 24 hours ending on Wednesday afternoon reported widespread rainfall over Himachal Pradesh, Haryana, North-East Rajasthan, Sub-Himalayan West Bengal, Sikkim, Coastal Karnataka and Lakshadweep.

It was fairly widespread over Uttarakhand, Punjab, Uttar Pradesh, the North-Eastern States, Gangetic West Bengal, Interior Karnataka and Tamil Nadu, Hardoi, Azamgarh, Gaya, Bankura and Sagar Islands.

MONSOON TAIL

International weather forecasters see the possibility of year 2010 monsoon, now on its final leg, lashing its tail over the south peninsula from this weekend.

As on Wednesday, the season has delivered 104 per cent rainfall, only two percentage points away from hitting the ‘upper circuit' as estimated in IMD's long-range forecast.

Most weather models see a phase of negative outgoing long wave radiation (OLR) enveloping Eastern and South-East Arabian Sea and contiguous Central Equatorial Indian Ocean and South-West Bay of Bengal from this weekend.

Negative OLR means less terrestrial radiation escaping into the atmosphere thanks to the presence of cloudiness over the region.

CYCLONIC WHIRL

The setting resembles monsoon onset conditions except that a cyclonic circulation sitting over the Bay and entering the Tamil Nadu coast would drive in easterlies over the peninsula to trigger the rains.

The Climate Prediction Centre (CPC) of the US National Weather Services is of the view that Peninsular India would slip under end-of-season monsoon rains during the week ending September 29.

Extended forecasts indicate that these rains could continue into the next week (September 30 to October 6) as well.

International Research Institute (IRI) for Climate and Society sees above normal rainfall for an area surrounding South Interior Karnataka until Saturday.

Contiguous regions of Tamil Nadu and Rayalaseema are also expected to witness fairly widespread to scattered rains, the IRI said.

In the North, heavy to very rains have been forecast over Nepal, East Uttar Pradesh, Bihar, Gangetic West Bengal and North-East India.

An IMD update on Wednesday showed the presence of convective clouds over parts of Himachal Pradesh, Punjab, Haryana, North-East Rajasthan, East Uttar Pradesh, North Bihar, South Chhattisgarh, South-East Arabian Sea, South-East Bay of Bengal and Andaman sea.

The IMD has also located an upper air cyclonic circulation over South Coastal Tamil Nadu and neighbourhood.

Its forecast valid until Saturday said that fairly widespread rain or thundershowers are likely over Jammu and Kashmir, Himachal Pradesh, Uttarkhand, West Uttar Pradesh, Punjab, Haryana, Chandigarh, Delhi and North Rajasthan during the next two days before gradually lifting.

Fairly widespread rainfall would also occur over the North-Eastern States, Bihar, West Bengal, Sikkim, South Peninsular India, Lakshadweep and Andaman and Nicobar Islands during this period.

Extended forecast until Monday indicated that the fairly widespread rainfall would continue over the Northeastern States and South Peninsular India.