The India Meteorological Department had listed 5 different weather systems that were active over mainland India on March 20; there was also an anticyclone system over the northwest Bay of Bengal
Gopalpur, a coastal town in Odisha. Photo for representation. Courtesy: iStock
On March 20, several places in Odisha recorded their lowest-ever maximum temperatures for the month. Bhubaneswar recorded a maximum temperature of 19.2 degrees Celsius (°C) — around 6°C lower than the previous record of 24.3°C set in 1970. Other cities such as Puri and Cuttack also recorded their lowest maximum temperatures for March on the day.
This happened because of extremely heavy early morning rainfall in these regions. The rainfall was caused by a cocktail of weather systems fuelled by a wobbly westerly jet stream. A jet stream is a band of winds circulating the Earth in the upper layers of the atmosphere that carries weather systems around the world.
All Odisha districts received large excess rainfall on March 20, with an incredible percentage excess of 10,000 per cent rainfall or more in seven of the districts. For instance, Bauda district received 47.8 millimetres (mm) of rainfall on the day, as against a normal rainfall of 0.1 mm. In absolute terms, Dhenkanal received the maximum rainfall of 49.4 mm which was 6,951 per cent more than the normal.
Rainfall also occurred in other states of eastern India such as Bihar, Jharkhand, West Bengal and Chhattisgarh on March 20.
The India Meteorological Department (IMD) had listed five different weather systems that were active over mainland India on March 20, while there was an anticyclone system over the northwest Bay of Bengal, off the Odisha coast.
Of the five land systems, four were in the lower layers of the troposphere — the lowest level of the atmosphere.
These were a cyclonic circulation over north Telangana, a trough/wind discontinuity from Kerala to north Telangana, a trough from northeast Madhya Pradesh to south Assam and a cyclonic circulation over Jharkhand and its neighbourhood. A trough from northeast Uttar Pradesh to east Vidarbha was present in the middle and upper layers of the troposphere.
Cyclonic circulations are swirls of winds that flow in the anti-clockwise direction in the Northern Hemisphere and induce low pressure systems and storms in the lower layers of the atmosphere.
A trough is an elongated low pressure system that can also induce storms and rainfall. An anticyclone is a high pressure area that is generally associated with disruptive weather in general by inducing cyclonic circulations.
“The storms this time of the year should still be dry. But the upper level westerly jet is very wobbly and almost split over the Indian region and is setting down a series of anticyclones over the Arabian Sea, Bay of Bengal and South China Sea,” Raghu Murtugudde, a climate scientist at the Indian Institute of Technology, Bombay and University of Maryland told Down To Earth.
“The two anticyclones (over the Arabian Sea and Bay of Bengal) appear to be meeting over central/eastern India to fire up some cyclonic circulations over central, eastern and north eastern India,” added Murtugudde.
There is still considerable warmth over the North Indian Ocean region towards the end of El Nino.
El Nino is the warmer-than-normal phase of the El Nino Southern Oscillation phenomenon in the equatorial Pacific Ocean and has caused global oceans to heat up in 2023-2024.
The current El Nino that began in July 2023, reached its peak around January and is now in its waning phase. The World Meteorological Organization and National Oceanic and Atmospheric Administration have said the El Nino may end by April-May 2024.
“The Indian Ocean generally warms towards the waning phase of the El Nino. So we are pumping in some extra moisture, which is acting like a steroid for weather. Unfortunately, we may soon have heatwaves to follow. So we have to be on guard,” says Murtugudde.
The thunderstorm activity and rainfall have since shifted to north eastern India on March 21 and March 22.
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