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Monsoon likely to arrive in Kerala on May 31, says IMD
The southwest monsoon, which delivers nearly 70% of the country’s rain between June and September and is crucial for its economy, is likely to be “above normal” at 106% of LPA
The monsoon is likely to arrive on the mainland a day ahead of schedule on May 31, the India Meteorological Department (IMD) said in a forecast on Wednesday, in an announcement that has a bearing on the livelihoods of many Indian farmers, food inflation, and the rural economy.
IMD added that its error margin was +/- 4 days. The normal date for monsoon onset over Kerala is June 1.
IMD’s operational forecasts of the date of the onset of monsoon during the past 19 years (2005-2023) were correct except in 2015, the agency said in a statement. To be sure, this is likely on account of the error margin which, this year for instance, gives the weather office a nine-day window to be right.
Last year’s monsoon arrived a week later than usual on June 8 – IMD predicted it would arrive on June 4 with +/- 4-day error margin.
The southwest monsoon, which delivers nearly 70% of the country’s rain between June and September and is crucial for its economy, is likely to be “above normal” at 106% of long-period average (LPA) with a model error of 5%, IMD said in its long-range forecast on April 15.
Last week, the National Oceanic and Atmospheric Administration (Noaa) of the US said this year could see the onset of the La Nina phenomenon, which could result in above normal monsoon rains in India.
The term El Nino refers to the large-scale ocean-atmosphere climate phenomenon linked to a periodic warming in sea-surface temperatures across the central and east-central equatorial Pacific. El Nino represents the warm phase of the El Nino/Southern Oscillation (ENSO) cycle while La Nina is just the opposite.
La Nina is the periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific that occurs every three to five years. These phenomenon are a part of natural climate variability. But, on top of these, the ongoing climate crisis also has an impact on rainfall and temperatures globally. In India, La Nina is associated with a strong monsoon, above average rains and colder winters.
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 dependant on agriculture for their livelihood (according to this year’s Economic Survey), a bountiful monsoon has a direct correlation with a healthy rural economy.
On Monday, IMD predicted that monsoon is likely to advance into the south Andaman Sea, some parts of the southeast Bay of Bengal and the Nicobar Islands around May 19, two days ahead of its normal onset date.
The advance of the southwest monsoon over Indian mainland is marked by monsoon onset over Kerala and is an important indicator characterising the transition from hot and dry season to a rainy season nearly across the country.
Relief from scorching summer temperatures is experienced as the monsoon progresses northward, usually in surges until finally covering the entire country around July 15.
IMD has been issuing operational forecasts for the date of monsoon onset over Kerala from 2005 onwards. An indigenously developed statistical model with a model error of ± 4 days is used for the purpose. It uses six predictors in the model — minimum temperatures over north-west India; pre-monsoon rainfall peak over south peninsula; outgoing long-wave radiation (OLR) over south China Sea which indicates cloud cover; lower tropospheric zonal wind over equatorial southeast Indian Ocean; OLR over Southwest Pacific Ocean; and upper tropospheric zonal wind over equatorial northeast Indian Ocean.
If after May 10, at least 60% of 14 stations — Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu and Mangalore — report rainfall of 2.5mm or more for two consecutive days, the onset of the monsoon over Kerala will be declared on the second day, provided the wind pattern is south-westerly and OLR is low. OLR represents the total radiation going to space emitted by the atmosphere or extent of cloudiness.
“We expect these conditions to be met around the normal time of monsoon onset over Kerala. The chances of cyclogenesis is very low over Bay of Bengal but we have to monitor how conditions evolve this week and next. Once monsoon advances to Andaman Sea around May 19 we will have a better idea of its progression,” said M Mohapatra, director general, IMD.
IMD’s Regional Specialised Centre for Tropical Cyclones over North Indian Ocean in its extended range forecast suggests a low probability of cyclone development over Bay of Bengal between May 17 and 23.
An updated forecast will be provided by IMD again during last week of May which is also expected to provide the probabilistic forecasts for the seasonal rainfall over the four homogenous regions of India (northwest India, central India, south Peninsula and northeast India) and monsoon core zone (MCZ).
