Sunday, August 22, 2010

N-E monsoon also may benefit from La Nina

International Research Institute (IRI) at Columbia University sees 96 per cent chance of La Nina conditions persisting through August to October this year.
In updated seasonal forecasts on Friday, the IRI assessed almost similar probability (95 per cent) of these conditions extending into November and December.

The IRI found elevated probabilities of the La Nina favourably impacting not just the ongoing south-west monsoon but the subsequent north-east monsoon as well.
As for expected rainfall trends for September-October-November, the IRI assessed as high the probabilities for excess precipitation for the entire western half of the country except the south-west Coast and North India (Jammu and Kashmir, Punjab, Haryana, Himachal Pradesh and Uttar Pradesh) where it would be normal.

During October-November-December, the north-west is expected to see the advent of the seasonal winter with a largely normal rainfall pattern.
Going into the December and January, the IRI sees elevated chances of Central and East-central India going through a lean phase in terms of recorded rainfall.
Meanwhile, India Meteorological Department (IMD) has indicated on Friday that the rainy weather over north-west India could sustain with more helpful atmospheric dynamics being thrown in.
Active convection and surplus moisture available is now expected to spin up a land-based low-pressure area, rare but not improbable, over West Uttar Pradesh by Monday.
A western disturbance is also forecast to enter the region subsequently, which could intensify the rainfall over the Himalayan foothills in Uttar Pradesh.
A causative upper air cyclonic circulation has been hanging in over West Uttar Pradesh and neighbourhood over the past few days.

An IMD update said that the last 24 hours ending Friday afternoon saw widespread rainfall being reported from Himachal Pradesh, Haryana, East Rajasthan, North Madhya Pradesh, Sub-Himalayan West Bengal, Sikkim, the North-eastern States and the West Coast.
It was fairly widespread over Jammu and Kashmir, Uttarakhand, Uttar Pradesh, Jharkhand, Gangetic West Bengal, Orissa, Marathwada, Vidarbha, Telangana and Interior Karnataka.
A satellite cloud imagery showed the presence of convective (rain-bearing) clouds over many parts of the country (outside Jammu and Kashmir, Gujarat, Mizoram and Tripura), South Bay of Bengal, Andaman Sea and East Arabian Sea.

An upper air cyclonic circulation has been traced to over Rayalaseema and neighbourhood and which has been spearheading precipitation over the Southern Peninsula.
A rain alert valid for the next two days said that isolated heavy to very heavy rainfall would occur over Himachal Pradesh, Uttarakhand, the Jammu division of Jammu and Kashmir, Sub-Himalayan West Bengal, Sikkim, Uttar Pradesh, Bihar, East Rajasthan, the north-eastern States, Coastal and South Interior Karnataka and Kerala.
Forecast valid until Monday spoke about the possibility of widespread rain or thundershowers over Himachal Pradesh, Uttarkhand, Sub-Himalayan West Bengal, Sikkim, the north-eastern States and Coastal Karnataka.

Fairly widespread rain or thundershowers would occur over Jammu and Kashmir, Punjab, Haryana, Chandigarh, Delhi, East Rajasthan, Uttar Pradesh, Bihar, Jharkhand, Madhya Pradesh, Konkan, Goa, Kerala, Interior Maharashtra, Interior Karnataka, Lakshadweep and the Andaman and Nicobar Islands.
Extended forecast until Wednesday said that widespread rainfall would occur over Sub-Himalayan West Bengal, Sikkim, Bihar, Uttar Pradesh, Haryana, East Rajasthan, Uttarakhand, Himachal Pradesh, the north-eastern States, Coastal Karnataka and Kerala.

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