 "Rain, Rainfall, monsoon")
The monsoon set in over Kerala on Thursday, two days ahead of its normal date, and has advanced into most parts of Northeast India, according to the India Meteorological Department (IMD).
Weather scientists said cyclone Remal, which swept through West Bengal and Bangladesh on Sunday, redirected the monsoonal flow towards the Bay of Bengal, potentially contributing to the early onset of the monsoon over the northeast.
In a bulletin, the IMD stated, "Southwest monsoon has set in over Kerala and advanced into most parts of Northeast India today, May 30, 2024."
Kerala has been receiving heavy rains for the past few days, resulting in a surplus May rainfall, according to weather office data.
On May 15, the weather department announced the onset of the monsoon over Kerala by May 31. The normal monsoon onset date for Kerala is June 1; for Arunachal Pradesh, Tripura, Nagaland, Meghalaya, Mizoram, Manipur, and Assam, it is June 5.
What does the 'onset of monsoon' mean?
The onset of the monsoon in Kerala signals the start of India's southwest monsoon season, spanning from June to September, responsible for over 70 per cent of the nation's annual rainfall. This event is of significant importance to India's economic schedule.
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According to the IMD, the onset of the monsoon signifies a significant shift in the extensive atmospheric and oceanic patterns across the Indo-Pacific region.
The department releases this announcement only upon meeting specific, well-defined criteria established in 2016. Primarily, the IMD assesses the uniformity of rainfall across designated areas, its strength, and prevailing wind velocities.
How does the IMD announce the onset of monsoon?
The onset of the monsoon in Kerala is officially announced on the second day if at least 60 per cent of the 14 designated stations—including Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu, and Mangalore—record rainfall of 2.5 mm or more for two consecutive days following May 10.
Monsoon in India
The IMD said on Monday that the central monsoon region of India is expected to experience above-average rainfall this season. "Quite confident that rainfall will be above average," the IMD said.
The weather department stated that above-normal rainfall would occur across the nation from June to September during the monsoon season.
In terms of quantity, the southwest monsoon's seasonal rainfall over India is projected to reach 106 per cent of the long-period average, with a model error margin of plus or minus four per cent, according to the IMD.
Mrutyunjaya Mohapatra, director-general of IMD, said the country is likely to experience normal rainfall (92-108 per cent of the long-period average of 166.9 mm) in June.
The IMD stated that "La Nina weather conditions are seen developing during July-September," indicating that India is "likely to experience normal rainfall (92-108 per cent of the long-period average of 166.9 mm) in June."
How do La Nina weather conditions impact the monsoon in India?
La Nina weather conditions can significantly impact the Indian monsoon, often leading to above-normal rainfall and increased flooding risk.
During a La Nina event, the sea surface temperatures in the equatorial Pacific Ocean become cooler than normal. This cooling strengthens the trade winds and enhances rainfall over the western Pacific and parts of Southeast Asia, including India.
The Asia-Pacific Economic Cooperation (APEC) Climate Centre also predicted that India is likely to experience above-normal rainfall during its peak monsoon season from July to September 2024, attributing this forecast to the anticipated transition from El Nino to La Nina conditions.
The IMD's Monsoon Mission Coupled Forecasting System has also indicated the potential development of La Nina conditions during the monsoon season in India.
Heatwave in India
The current heatwave condition in India is severe, with temperatures soaring between 44 and 53 degrees Celsius in several regions, including Northwest and Central India.
The India Meteorological Department (IMD) has issued warnings for severe heatwave conditions in various states, including Rajasthan, Punjab, Haryana, Chandigarh, Delhi, and Gujarat. The heatwave is expected to persist in some areas until the onset of the monsoon season.
Temperatures in Delhi on Wednesday rose to its highest-ever level at 52.3 degrees Celsius, according to data from the India Meteorological Department (IMD). However, a sudden light drizzle brought some relief to Delhiites on Wednesday evening.
The surge in temperature was recorded a day after Delhi nearly reached 50 degrees Celsius at three of its weather stations in the outer areas. Mungeshpur, Narela, and Najafgarh weather offices have been reporting extreme temperatures this week.
On Sunday, Rajasthan's Phalodi registered the highest temperature in India at 49.8 degrees Celsius, with Delhi's Mungeshpur following at 48.3 degrees Celsius. Jhansi recorded 47.7 degrees Celsius, while Punjab's Faridkot experienced 47.4 degrees Celsius.
When is a heatwave declared?
A heatwave is declared over a region "when the actual maximum temperature remains 45 degrees Celsius or more irrespective of the normal maximum temperature," the Centre states.
According to the IMD, a heatwave is declared "if the maximum temperature of a station reaches at least 40 degrees Celsius or more for plains, 37 degrees Celsius or more for coastal stations, and at least 30 degrees Celsius or more for hilly regions" for two or more days.
(With agency inputs)
