Heavy rain in Eastern India, March 20: Weather analysis.
On March 20, several places in Odisha experienced their lowest-ever maximum temperatures for the month. Bhubaneswar recorded a maximum temperature of 19.2°C, which is approximately 6°C lower than the previous record set in 1970. Other cities like Puri and Cuttack also reported their lowest maximum temperatures for March on that day.
This unusual weather phenomenon was caused by an intricate interplay of weather systems fueled by a wobbly westerly jet stream. Let’s break down the factors contributing to this event:
Weather Systems Involved:
► The India Meteorological Department (IMD)identified five different weather systemsactive over mainland India on March 20.
► Additionally, there was an anticyclone systemover the northwest Bay of Bengal, off the Odisha coast.
► Among these systems, four were in the lower layers of the troposphere, which is the lowest level of the atmosphere.
These systems included:
■ Cyclonic circulation over north Telangana
■ Trough/wind discontinuity from Kerala to north Telangana
■ Trough from northeast Madhya Pradesh to south Assam
■ Cyclonic circulation over Jharkhand and its vicinity
In the middle and upper layers of the troposphere, there was a trough extending from northeast Uttar Pradesh to east Vidarbha.
Impact on Odisha:
► All Odisha districts received large excess rainfall on March 20.
► Some districts experienced an incredible percentage excess of 10,000 per cent or more compared to normal rainfall.
For instance:
■ Bauda district received 47.8 mm of rainfall (compared to a normal of 0.1 mm).
■ Dhenkanal received the maximum rainfall of 49.4 mm, which was 6,951 per cent more than the normal.
■ Similar rainfall occurred in other states of eastern India, including Bihar, Jharkhand, West Bengal, and Chhattisgarh.
Wobbly Westerly Jet Stream:
► The upper-level westerly jet stream was unusually wobbly and almost split over the Indian region.
► This led to the formation of a series of anticyclones over the Arabian Sea, Bay of Bengal, and South China Sea.
► The convergence of these anticyclones over central/eastern India contributed to the development of cyclonic circulations.
El Nino Influence:
► Despite the waning phase of the El Nino(warmer-than-normal phase of the El Nino Southern Oscillation), there is still considerable warmth over the North Indian Ocean region.
► The Indian Ocean tends to warm during the waning phase of El Nino.
► This extra warmth is acting like a steroid for weather, potentially leading to more extreme events.
► Unfortunately, this could mean that heatwavesmay follow, so vigilance is necessary.
As of now, the thunderstorm activity and rainfallhave shifted to northeastern India on March 21 and March 22. Understanding these complex weather patterns is crucial for disaster preparedness and mitigation.
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