Forecast for the 2020 Southwest Monsoon Onset over Kerala
The National Weather Forecasting Centre of the India Meteorological Department,has come out with the forecast of Monsoon onset over Kerala. The silent features are given below:
This year, the onset of southwest monsoon over Kerala is likely to be slightly delayed as compared to normal date of onset of 1st June. The monsoon onset over Kerala this year is likely to be on 5th June with a model error of ± 4 days.
1. Background
Advance of the southwest monsoon over Indian main land is marked by monsoon onset overKerala and is an important indicator characterizing the transition from hot and dry season to a rainyseason. As the monsoon progresses northward, relief from scorching summer temperatures isexperienced over the areas. Southwest monsoon sets over Kerala on 1st June with a standarddeviation of about 7 days. India Meteorological Department (IMD) has been issuing operationalforecasts for the date of monsoon onset over Kerala from 2005 onwards. An indigenouslydeveloped state of the art statistical model with a model error of ± 4 days is used for the purpose.
The 6 Predictors used in the models are; i) Minimum Temperatures over North-west India, ii) Premonsoonrainfall peak over south Peninsula, iii) Outgoing Long wave Radiation (OLR) over southChina Sea, (iv) Lower tropospheric zonal wind over southeast Indian Ocean, (v) upper troposphericzonal wind over the east equatorial Indian Ocean, and (vi) Outgoing Long wave Radiation (OLR)over the south-west Pacific region.
IMD’s operational forecasts of the date of monsoon onset over Kerala during the past 15 years (2005-2019) were proved to be correct except in 2015. Forecast verification for the recent 5years (2015-2019) is given in the table below.:
Year Actual Onset Date Forecast Onset Date
2015 5th June 30th May
2016 8th June 7th June
2017 30th May 30th May
2018 29th May 29th May
2019 8th June 6th June
