Thursday, March 25, 2010

Monsoon may lack usual June fizz over west coast

The onset phase of the southwest monsoon later this year might throw up normal to just-less-than-normal rainfall along the west coast due to a combination of adverse factors.

According to Dr Jing-Jia Luo, Senior Scientist with the Tokyo-based Research Institute for Global Change (RIGC), monsoonal rains over India would be driven mostly by moisture transport from the Bay of Bengal this year.


The moisture-laden easterlies would be steered in this manner by an anti-cyclone sitting in the higher levels of the atmosphere.

The winds are shown to curve to the northwest from the plains of Tamil Nadu bringing excess rain to this region.

In comparison, the Arabian Sea arm that sets up the onset along the southwest coast, is shown to be weak and less productive.

This trend may last for the entire June, Dr Jing-Jia said in a communication to Business Line.

But he maintained the overall ‘normal' outlook for monsoon, largely underwritten by a brewing La Nina, the monsoon-friendly alter ego of El Nino, towards August.

Forecasts for July-August-September made by the International Research Institute (IRI) for Climate and Society corroborate this outlook.

IRI sees excess rains over the west coast, peninsular India and parts of north and northwest India during this phase.


Updated seasonal forecasts from the European Centre for Medium-Range Weather Forecasting (ECMWF) join the RIGC in predicting the possibility of Bay of Bengal getting into hyper activity, especially in June.

Significantly, Dr Jing-Jia also said RIGC has withdrawn the outlook for a positive Indian Ocean Dipole (IOD), another monsoon-enabler, from September onwards.

The warming anomaly in the Indian Ocean is instead shown to shift to the east, which takes away an additional prop for the monsoon.

Meanwhile on Wednesday, a warning issued by India Meteorological Department (IMD) and valid for the next 24 hours said heat wave conditions would prevail over parts of Madhya Pradesh, Vidarbha, Chhattisgarh, Telangana and interior Orissa.

Isolated thundersquall is likely to occur over Arunachal Pradesh, Assam and Meghalaya during next two days in what is a prelude to the unfolding of the seasonal convective activity and thundershowers (Nor'westers or Kal Baisakhi) by Sunday.

This would happen as an incoming western disturbance on Thursday wades its way into east and northeast India. A preceding westerly system passing through the region has already thrown open a north-south trough from sub-Himalayan West Bengal to north Bay of Bengal. It persisted on Wednesday, facilitating moisture incursion.

Heat wave to severe heat wave conditions have been prevailing over many parts of Rajasthan, south Uttar Pradesh, Chhattisgarh, Jharkhand, some parts of Madhya Pradesh and isolated pockets of Haryana, Bihar and Himachal Pradesh. Heat wave conditions prevailed also over some parts of Vidarbha, interior Orissa and isolated pockets of Telangana and West Bengal.

The highest maximum temperature of 43.9 deg Celsius was recorded at Chandrapur in Maharashtra during the 24 hours ending Wednesday morning.

Satellite imagery showed convective (rain-generating) clouds over Arunachal Pradesh and low to medium clouds (partly clouded conditions) over Jammu and Kashmir, Himachal Pradesh, Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura and south Andaman Sea.

Forecast until Saturday spoke about the possibility of scattered to fairly widespread rain or thundershowers accompanied with isolated thundersquall over the Northeastern States during the next three days.

Forecast until Monday said fairly widespread rain to thundershowers accompanied with isolated thundersquall are likely over the North-Eastern States. Scattered rain or snow may occur over Jammu and Kashmir while it would be isolated over Himachal Pradesh.

No comments:

Post a Comment