Thursday, April 14, 2016

South Westerly Monsoons 2016 : El Nino 2015 and IMetD Long Range Forecast (LRF) 2016

S W Monsoon 2016 (01Jun-30Sep2016)
Backdrop of the meteorological conditions
1. Though El Nino is still ‘strong’, it is declining and by mid-monsoons, it is expected to reach NUETRAL level. This weakening of the El Nino is expected to push up rainfall especially during the latter half of 2016 monsoons.
2. Some climate models indicate possibility of La Nina effect, which is opposite of the EL Nino during the last months of the monsoon.
3. IOD (Indian Ocean Dipole) though currently slightly negative, is expected to become positive during the monsoons and then become neutral as the monsoon ends. IOD becoming +ve and neutral is good for the monsoon season.
Highlights of the First Stage Long Range Forecast (LRF)
1. Rainfall for the country as a whole is likely to be above the normal (890mm) ie between 104-110% of the long period average rainfall. Quantitatively, rainfall for the country is likely to be 106% (ie 940mm) of the long period average with a possible error margin of +/- 5%.
2. There is 94% probability that monsoon season rains would be normal to excessive and only 1% probability that the monsoon would be deficient.
3. Though the Monsoons are expected to arrive by the due date, more exact forecast will only be possible 2 weeks ahead of the onset.
4. By and large the distribution of rain is expected to be good, however some parts of the NE region and SE parts (parts of Tamil Nadu and adjoining Rayalaseema districts) of the peninsular may have less than normal rain.
Quantitative, month-wise temporal distribution of rain during the monsoons is expected to be good and to accentuate from mid-monsoons onwards.
5. Due at least in part to a strong El Nino, last year we had 14% below average rain in the country but this year we expect 6% above normal rain (890mm).
6. Extremely heavy rainfall events may occur but that can only be predicted in the Medium Range Forecasts.

You can read the Press Brief of the LRF here

Praful Rao,
Dist Darjeeling

No comments: