Monsoon will hit Kerala on May 31, the India Meteorological Department (IMD) informed on Wednesday with a margin of error of four days both before or after May 31.
The advance of the southwest monsoon over the Indian mainland is marked by monsoon onset over Kerala and is an important indicator characterizing the transition from hot and dry season to a rainy season. As the monsoon progresses northward, relief from scorching summer temperatures is experienced over the areas. Southwest monsoon normally sets in over Kerala on 1st June with a standard deviation of about 7 days.
India Meteorological Department has been issuing operational forecasts for the date of monsoon onset over Kerala from 2005 onwards. An indigenously developed state-of-the-art statistical model with a model error of plus or minus 4 days is used for the purpose. The 6 predictors used in the models are
- Minimum Temperatures over North-west
- Pre-monsoon rainfall peak over south Peninsula
- Outgoing Long wave Radiation (OLR) over south China Sea
- Lower tropospheric zonal wind over equatorial southeast Indian Ocean
- Outgoing Long wave Radiation (OLR) over Southwest Pacific Ocean
- Upper tropospheric zonal wind over equatorial northeast Indian Ocean
IMD's operational forecasts of the date of monsoon onset over Kerala during the past 19 years (2005-2023) were proved to be correct except in 2015.
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