Hottest to coldest: March logs drastic shift in weather pattern
The first two weeks of the month were among the hottest, the second half, among the coldest which could put it in the top 10 coldest March in the past 73 years.
March 2023 has seen a radical change in temperatures compared to historical averages. The first two weeks of the month were among the hottest and the second half, among the coldest which could put the whole month in the top ten coldest March in the past 73 years.
The average maximum for India up to March 29 is 30.35 degrees Celsius, according to India Meteorological Department’s (IMD) gridded dataset. This is 0.96 degrees below the 1981-2010 average for this interval, considered to be normal by the IMD, and the 12th coolest since 1951, the first year for which IMD has gridded data. This is the polar opposite of the maximum readings in February, which was the 13th warmest since 1951.
To be sure, the beginning of the month did not suggest a cool March. IMD’s forecast for March-May period on February 28 said that March was expected to be warmer than normal in most parts of the country. The first two weeks of March followed this early forecast. They were 1.1 and 1 degree warmer than normal, and both were the 22nd warmest since 1951. This was not on account of a few extreme days. All days except March 7 were warmer than normal from March 1 to March 15.
Also Read: Soon, weather agency IMD forecasts to include ‘real feel’ factor: What it means
After the first two weeks, however, temperatures climbed down in most parts of India. From March 16 onward, every day has been at least 1.3 degrees cooler than normal. On average, the weeks ending March 21 and March 28 were 3.5 and 2.3 degrees cooler than normal. This made the former the coolest week ending March 21 since 1951 and the latter the fourth coolest. The average temperature during the week ending March 21 (28.44 degrees) was slightly lower than even the average for February (28.46 degrees).
The record-breaking cold in the third week of March was caused by several factors that worked in tandem. According to an IMD press release, these were two active western disturbances, cyclonic circulations over Rajasthan, a trough or region of low pressure in southern parts of peninsular India and east central India, westerly winds of speed 120-200 kilometres per hour sometimes in the upper troposphere, and moisture from Bay of Bengal and Arabian Sea due to anti-cyclonic circulation there. As HT reported earlier (https://bit.ly/3zewca5), these factors led to sustained rainfall and thunderstorm, often accompanied with hailstorm.
Also Read: Rainfall in March not due to climate change: IMD
The factors listed above affected most parts of the country. Therefore, only 10 of 30 states and union territories for which this calculation is possible using IMD’s gridded dataset have turned out warmer than normal in March so far. Even among these 10, only six are warmer by more than 0.5 degrees. These states are Assam, Punjab, Tripura, Kerala, Manipur, and Mizoram, and only the latter four are warmer by more than a degree. The maximum fell the most below normal in Sikkim (4.99 degrees), Jammu and Kashmir (2.61 degrees), Meghalaya (1.65 degrees), Telangana (1.61 degrees), and Maharashtra (1.47 degrees).
Delhi is another example of how the cooling differed in magnitude across different parts of the country. The average maximum in Delhi so far is 0.31 degrees below normal, making this March only the 34th coolest for the national capital. Although Delhi also followed the trend of a warm first half followed by a cool second half, it has ranked higher in degree of warming than the national average. The first two weeks of March in Delhi were 2.1 and 1.9 degrees warmer than normal; and ranked 19th and 18th warmest. The next two weeks were 2.8 and 2.5 degrees cooler than normal, making them the ninth and tenth coolest.
Will this period of widespread cooling end with March? Not likely, if IMD’s forecast for the next two weeks is correct which says that most of the country is going to be cooler than normal up to mid-April, with little warming even in the period after.
