A low-pressure is now expected to pop up over the Bay of Bengal by Sunday as a persisting upper air circulation descends to lower levels and matures.
In the run-up to this likely denouement, the Andaman and Nicobar Islands are expected get buffeted by rains or thundershowers over the weekend, India Meteorological Department (IMD) said on Friday.
WARMER SEAS
The seas have warmed up to well above 30 deg Celsius, which is more than enough to sustain the brewing ‘low.’
This would also help steer the flows in the Bay to being more easterly to southeasterly, after having seen the back of a harmful ‘ridge’ or high-pressure region that has been pushed away.
The ‘low’ has been delayed this year from mid-April, which is normally the time around which the Bay gets its act together.
Meanwhile, peninsular India and adjoining east India, constituting two-thirds of the landmass in south, central and east-central regions, has witnessed surplus summer rains for almost two months between March 1 and April 27.
SURPLUS RAINS
Rainfall deficiencies have been confined to extreme west and northwest, according to an update provided by the IMD.
The Gujarat and Sourashtra region, Madhya Pradesh, Rajasthan, Punjab, Haryana and Delhi, Himachal Pradesh and Uttar Pradesh totted up varying deficiencies.
Jammu and Kashmir was the only Met subdivision to record a normal (+5 per cent) rainfall in the northwest while only Gujarat was totally devoid of any rainfall.
Among the Met subdivisions which surprised on the upside with surplus rainfall thus far during the season are Telengana (+43 per cent); Rayalaseema (+28 per cent); Vidarbha (+75 per cent); Chhattisgarh (+117 per cent); Bihar (+36 per cent); Gangetic West Bengal (+101 per cent); north interior Karnataka (+67 per cent); and south interior Karnataka (+103 per cent).
COOLING TREND
The larger Maharashtra, Andhra Pradesh, Orissa and Jharkhand states also found themselves falling in the ‘normal’ category.
One significant fall-out of the rainfall pattern has been the less than normal cooling of these regions and total absence of heat waves that normally take a toll on human and animal lives.
Some weather watchers have also tended to view with this caution in terms of the likely impact on the impending of the monsoon that drives essentially on land-sea surface temperature contrasts.
Global weather models are, however, of the view that sustained heating of the land surface has already started from northwest India and would filter into central, east-central and parts of peninsular India from the coming week onwards.
THUNDERSHOWERS
Meanwhile, fairly widespread overnight rain or thundershowers has been reported from Andaman and Nicobar Islands overnight on Friday.
It was scattered over sub-Himalayan West Bengal, Sikkim, Meghalaya and Tripura and isolated over Jammu and Kashmir, east Uttar Pradesh, Orissa, south interior Karnataka and Tamil Nadu.
On Thursday, maximum temperatures were above normal by 2 to 4 deg Celsius over some parts of Punjab, east Rajasthan, northwest Madhya Pradesh.
But they continued to be below normal by 2 to 4 deg Celsius over Chhattisgarh, Jharkhand, Tripura and Orissa.
HIGHEST MAXIMUM
The highest maximum temperature of 44.0 deg Celsius was recorded at Churu (Rajasthan), Jalgaon (Maharashtra) and Khargone (Madhya Pradesh) on Thursday.
Satellite pictures early on Friday morning showed the presence of convective (rain-bearing) clouds over parts of Jammu and Kashmir, Bihar, sub-Himalayan West Bengal, Sikkim, Assam, Kerala, Tamil Nadu, south and east-central Bay of Bengal and the Andaman Sea.
The western disturbance over north Pakistan and adjoining Jammu and Kashmir now lies over Jammu and Kashmir. It would affect western Himalayan region and adjoining plains of northwest India until Monday.
