Monsoon onset over Kerala may be delayed by 3-6 days
The onset of monsoon over Kerala will be delayed by three days and is expected to happen on June 4, IMD said in its forecast on Tuesday.
The onset of monsoon over Kerala will be delayed by three days and is expected to happen on June 4, the India Meteorological Department (IMD) said in its forecast on Tuesday, adding that its error margin was +/- 4 days. The normal date for monsoon onset over Kerala is June 1.
Private forecaster Skymet Weather has forecast the date as June 7, with an error margin of +/- 3 days.
While IMD did not say anythingabout the progression of the monsoon across India, Skymet said it will advance sluggishly over peninsular India.
A bountiful monsoon is critical for the kharif (or monsoon) crop, to keep inflation under control, and to boost the rural economy. According to India’s agriculture ministry, 51% of India’s farmed area, accounting for 40% of production, is rain-fed, making the monsoon critical. With 47% of the country’s population dependent on agriculture for their livelihood (according to this year’s Economic Survey), a bountiful monsoon has a direct correlation with a healthy rural economy. For instance, Skymet said in a statement the expected sluggish advancement of the monsoon “may not augur well for kharif sowing.”
Also Read: IMD forecast show a warmer start to June in Delhi
This year’s monsoon will also be closely watched because of the presence of an El Nino effect, a weather phenomenon that has a correlation with poor monsoons. While neither IMD nor Skymet
IMD has also predicted a “normal” monsoon at 96% (with an error margin of +/-5%) of the long period average or LPA. The LPA for monsoon season between June to September is 87cm, which is calculated for the period of 1971 to 2020. Skymet Weather, however, has forecast “below normal” rainfall during the monsoon season.
There is a 35% forecast probability of a “normal” monsoon this year followed by a 29% probability of a “below normal” monsoon; a 22% probability of a “deficient” monsoon and only 11% probability of an “above normal” monsoon and only 3% of an “excess” monsoon year, IMD said last month.
IMD’s operational forecasts of the monsoon onset over Kerala in the past 18 years (2005-2022) have proven correct, with 2015 being the only exception, the weather office said in a statement. In 2015,the forecast was for May 30 and the actual onset was on June 5.
The six predictors of monsoon onset used in the models by IMD are: minimum temperatures over northwest India; pre-monsoon rainfall peak over south Peninsula; outgoing long wave radiation (OLR) over south China Sea (OLR represents the total radiation going to space emitted by the atmosphere or extent of cloudiness); lower tropospheric zonal wind over Southeast Indian Ocean; mean sea-level pressure over Subtropical NW Pacific Ocean; and upper tropospheric zonal wind over North East Indian Ocean.
“It is not a major delay. From the normal date of onset, we are only suggesting a three-day delay with model error of 4 days. So, there is nothing to be worried about,” said M Mohapatra, director general, IMD.
Last year, IMD forecast monsoon onset on May 27 and the actual onset was on May 29. In 2021, the actual monsoon onset on June 3 was only three days behind IMD forecast of May 31. In 2020, IMD forecast onset to be on June 5 while actual onset was on June 1. In 2019, IMD’s onset forecast was June 6 and actual onset was on June 8 while in 2018, IMD forecast and actual onset took place on May 29.
The National Oceanic and Atmospheric Administration of US on May 11 forecast that there is an 80% chance of El Nino establishing in May, June and July and 90% chance in June, July and August. El Nino is characterised by an unusual warming of waters in the eastern equatorial Pacific, which has a high correlation with warmer summers and weaker monsoon rains in India.
“There is no one-to-one relationship of delayed monsoon onset or slow progression with El Nino,” said Mohapatra.
M Rajeevan, former secretary, ministry of earth sciences, said: “Though El Nino is not considered by the models used to predict monsoon onset, we know that monsoon onset is often delayed in El Nino years. The heating over northwest India during pre-monsoon months which is a feature considered by models for monsoon onset was not very good this year. Plus, the Madden Julian Oscillation or the northward propagation of a band of clouds happened late this year during the pre-monsoon season around April 30.”
Monsoon onset normally happens between 30 to 40 days after that, so there can be a number of factors that can delay it, Rajeevan explained.
“El Nino threshold has already been crossed but it is declared by authorities three months after it is established. But monsoon doesn’t understand declaration of El Nino. The El Nino features must be already impacting monsoon,” he said. “It’s too early for us to say how monsoon will behave after onset takes place. It’s important to note that El Nino threshold was crossed much before the date global models predicted.”
HT reported on May 1 that an uncharacteristically cooler start to the summer, which is likely to persist for a few more weeks in several parts of the country, may hurt the arrival of the crucial monsoon season, weather scientists have said, at a time when the rainy season is expected to anyway be sapped by the Pacific warming phenomenon El Nino.
Skymet also offered another explanation for the delayed onset of the monsoon. A powerful cyclone “Fabien” is moving over the South Indian Ocean, it said in its statement. “The hurricane-strength weather system will take nearly one week to clear the area. This monster storm is restricting the cross-equatorial flow and the build-up of the monsoon stream. Also, the Arabian Sea continues to host an anticyclone over the central parts in the lower levels of the atmosphere. This acts as a deterrent for the smooth streaming of Monsoon flow from the Arabian Sea to the West Coast. ”
