The India Meteorological Department (IMD) on March 1 announced this year’s summer season onset officially over India. The Met department released the ‘Seasonal Outlook for temperatures for March to May 2021’. The season ahead is expected to be warmer than usual over most regions of India except some southern states.
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Most meteorological sub-divisions and regions along the North, Northwest and Northeast India, in addition to a few areas in the East will experience above normal maximum temperatures (seasonal) during March, April and May. Above normal minimum temperatures (seasonal) are also predicted over regions lying along the foothills of the Himalayas, northeastern and southern states during the next three months.
But, most states in the South and Central India would experience normal minimum temperatures during the night, as they are expected to remain close to normal or below for this time of the year.
The IMD has issued this forecast on the basis of February’s initial weather conditions and using the reference of its previous summer forecasts issued annually between 2003-2018.
In April, the IMD will issue an updated seasonal outlook for April to June months.
The regions along the Indo Gangetic Plains — Punjab, Chandigarh, Haryana, Delhi, Uttar Pradesh and Bihar are likely to experience maximum temperatures that will be above normal during March, April and May. Here, the maximum temperatures can go up to 0.71 degree Celsius over the normal Long Period Average (LPA).
Odisha, Chhattisgarh and Konkan in Maharashtra have been categorically warned of a hotter summer season this year, where the day temperature anomaly can fluctuate between 0.25 and 0.86 degrees over the normal LPA.
The Met officials have stated that nights could be warmer than usual during this season mainly over the southern states.
“This could be due to the possibility of moisture conditions created locally or rainfall activity which leads to warm and hot nights,” said D Sivanand Pai, head, Climate Research and Services at IMD, Pune.
While both warm days and nights would dominate the weather over Punjab, Haryana, Chandigarh, Delhi and Uttar Pradesh, warm nights would dominate west Madhya Pradesh, Gujarat, Rajasthan, Kerala, Tamil Nadu, Assam, Meghalaya, Manipur, Mizoram, Nagaland and Arunachal Pradesh this summer.
India is prone to heat waves conditions, which is declared when the maximum temperatures rise over 4 degrees from normal recorded at a location.
It is not possible to predict the exact number of heatwave events, their geographical expanse or intensity in a Seasonal Outlook, which is given for a period of three months, in this case, and for the entire country.
But past records suggest that heatwaves are common along the Core Heatwave Zone (CHZ) areas every summer. The CHZ covers Rajasthan, Punjab, Haryana, Chandigarh, Delhi, West Madhya Pradesh, Uttar Pradesh, Chhattisgarh, Odisha, Vidarbha in Maharashtra, parts of Gangetic West Bengal, Coastal Andhra Pradesh and Telangana.
Hotter summers are likely along some of these states.
“Some of these regions fall under the Core Heatwave Zone. So, these states should expect normal or even more heatwave events this year. The heatwave predictions and their intensity can best be forecast as the season progresses using the IMD’s Extended Range Predictions issued for up to four weeks in advance,” Pai said.
La Nina is a Pacific Ocean phenomenon when the sea surface temperatures along its central and equatorial belt remain cooler than normal. Even though higher temperatures are associated with El Nino and the opposite scenario for La Nina, both these ocean conditions influence temperatures globally.
At present, a moderate-intensity La Nina prevails over the Pacific Ocean. Despite the current nearing the end of its cycle, the Met office has confirmed that it will prevail all through summer with its remnants lingering during June, as well.
Pai said, “La Nina favours cooler than normal temperatures and it is not the only dominating factor affecting the temperatures during summer months. There are other atmospheric and ocean parameters, local wind factors all of which together decide the temperatures during summer season over India.”
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