30-05-2024
IMD announced Monsoon onset over Kerala today.
I would say it’s bureaucracy. Actually, IMD missed a trick. There were ideal conditions to announce the monsoon over Kerala a few days ago, between the 20th and 25th of May, but IMD didn’t like it.
As per me, Actually Monsoon moved into South Kerala few days back around 20-23rd May.
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Let’s analyse this extensively.
IMD defined certain Criteria to announce monsoon onset over Kerala
1. Rainfall 
If after 10th May, 60% of the available 14 stations enlisted*, viz. Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu and Mangalore report rainfall of 2.5 mm or more for two consecutive days, the onset over Kerala be declared on the 2nd day, provided the following criteria are also in concurrence.
Rainfall Criteria is fulfilled
2. Wind Field 
Depth of westerlies should be maintained upto 600 hPa, in the box equator to Lat. 10ºN and Long. 55ºE to 80ºE. The zonal wind speed over the area bounded by Lat. 5-10ºN, Long. 70-80ºE should be of the order of 15 – 20 Kts. at 925 hPa. The source of data can be RSMC wind analysis/satellite derived winds.
Depth of Westerlies Criteria is not fulfilled
Instead, we can see Easterlies/North easterlies over Kerala and adjoining parts of SE Arabian Sea at 3.1 km and above.
The Zonal wind speed Criteria is fulfilled.
3. OLR
INSAT derived OLR value should be below 200 wm-2 in the box confined by Lat. 5-10ºN and Long. 70-75ºE.
OLD criteria is fulfilled
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So, we can say 2 out of 3 mandatory criteria have been met.
They may say it’s a feeble onset just to preserve the accuracy of their forecast.
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IMD ? ??? ??????? ???????? ??????? ???? ??.
????? ???? ?? ? ?????????? ??. IMD ?? ???? ??. ?? 20 ?? 25 ?? ??????? ??????? ?????? ????? ???? ???? ?????????? ???? ????? ???. ?? IMD ?? ? ???? ?? ??????? ??? ???? ????
???? ?? ???? ?????? 20 ?? 23 ?? ??????? ?????? ???? ???????? ??????? ??????? ??.
IMD ? ??????? ?????? ????? ???? ???? ?????? ??????? ????? ???? ??.
1. Rainfall
2. Wind Field
3. OLR
??? ??? ????? ?? ? 3 ???? ?????? 2 ??????? ???????? ???? ??.
1. Rainfall
2. OLR
??????,
Wind Field ?? ?????? ???????? ???? ???….
??? ???? ???? ?????? ??????-????? ??? ???? ?? ?????? ?????? 3.1 km ????? ?? ?????, ?????????? ??? ????? ?????? ???? ?????????? ??, ?? ???????? ???? ???? ?????? ?????? ?????? ??….
IMD ???? ????????? ???? ???? ?? ????? Onset ??? ??? ??.
??????? ????? ????