IMD declares Onset of Southwest Monsoon over Kerala

As per IMD… Southwest Monsoon has set in over Kerala today, the 3 rd June, 2021, against the normal date of 1st June. 

The Northern Limit of Monsoon (NLM) passes through lat. 10 0N/ Long. 600E, lat. 10 0N/ Long. 700E, Kochi, Palayamkottai, lat. 9 0N/ Long. 80 0E, 12°N/85°E, 14°N/90°E and 17°N/94°E. 

Southwest monsoon is likely to advance into remaining parts of south Arabian Sea, some parts of central Arabian Sea, remaining parts of Kerala & Lakshadweep, some more parts of Tamil Nadu & Puducherry, some parts of coastal & south interior Karnataka, Rayalaseema and some more parts of south and central Bay of Bengal during next 2 days.

Southwest Monsoon has advanced into some parts of south Arabian Sea, Lakshadweep area, south Kerala, south Tamil Nadu, remaining parts of Comorin – Maldives area and some more parts of southwest Bay of Bengal today, the 3rd June 2021.

The following criteria were fulfilled to declare the onset of monsoon over Kerala:

a) More than 60% of the 14 rainfall monitoring stations reported rainfall 2.5 mm or more on past 2 days consecutively. Also the spatial distribution of rainfall over Kerala remained to be fairly widespread during past 2 days.

b) Westerly winds have strengthened in the lower levels (wind speed upto 20 knots) and Satellite derived winds suggest that 15-20 knots westerly winds prevail upto 600 hPa as on today.

c) There is persistent convection (cloudiness indicated by Outgoing Longwave Radiation values <200 Wm-2 ) from satellite imagery and coastal Doppler Weather Radars over Lakshadweep and adjoining southeast Arabian Sea along & off Kerala coast and Maldives area.

Apart from the above, the following synoptic systems are prevailing over the region. a) An east west shear zone runs from south Arabian Sea to southeast Bay of Bengal across southern most parts of peninsular India in the mid-tropospheric levels. b) An off shore trough at mean sea level runs off Karnataka – Kerala coasts.