The India Meteorological Department (IMD) said on Friday that monsoon is likely to hit Kerala on May 26 with a model error of ±4 days. The normal arrival date of the monsoon is June 1. Last year, monsoon rains reached Kerala on May 24.
The IMD extended range forecast shows heavy rainfall along southern parts of the West Coast from May 14 to 28.
The advance of the southwest monsoon over the Indian mainland is marked by the onset of the monsoon over Kerala, an important indicator that marks the transition from the hot and dry season to the rainy season.
As the monsoon advances north, relief from the scorching summer temperatures is felt in the regions. The southwest monsoon usually blows over Kerala on June 1 with a standard deviation of about 7 days.
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Monsoon history
The IMD has issued operational forecasts for the monsoon onset date over Kerala from 2005 onwards. A sophisticated statistical model developed locally with a model error of ± 4 days is used for this purpose.
The six predictors used in the models are; 1) minimum temperatures over northwest India, 2) peak pre-monsoon rainfall over the southern peninsula, 3) outgoing longwave radiation (OLR) over the South China Sea, (4) low-tropospheric winds over the southeastern Indian Ocean, (5) outgoing longwave radiation (OLR) over the southwest Pacific, and (6) low-tropospheric winds over the northeastern Indian Ocean. OLR is the total radiation emitted from the atmosphere into space, or the extent of the clouds.
Seasonal models predicted that an El Niño climate pattern would form between May and July of this year, and it could be the strongest ever.
In India, El Niño is associated with harsher summers and weaker monsoons. Monsoon rainfall over the country is likely to be below normal at 92% of the long period average (LPA) with a margin of error of +/- 5%, the IMD said in the first phase of its long-range forecast for the monsoon season.
The average seasonal rainfall over the country as a whole during the period 1971-2020 is 87 cm.
The spatial distribution indicates that below-normal monsoon rainfall is likely over many parts of the country except some areas in northeastern, northwestern and southern peninsular India, where normal to above-normal rainfall is likely.
