Revising its earlier prediction, private weather agency Skymet has lowered its monsoon forecast from 102 per cent to 98 per cent even as it maintained that the country will receive “normal” rainfall during the year.
It has also revised its prediction for July to 84 per cent as against the earlier forecast of 104 per cent.
Anything less than 90 per cent of the Long-Period Average (LPA) is termed “deficient” rainfall while 90-96 per cent of LPA is considered “below normal”. Again, rainfall at 96-104 per cent of the LPA is “normal” with 104 to 110 per cent taken to be above normal. Anything over that is “excess”.
Ninety-eight per cent is, however, on the “negative” side of normal monsoon.
“Taking cognisance of July rain, and the updated August and September forecast, we are revising the monsoon forecast to 98 per cent (normal) of the LPA from 102 per cent issued in April (error margin of plus/ minus 4 per cent).
“After an above normal June (plus 16 per cent), July is going to end with (minus 15 per cent). This is near normal, but less than our initial forecast (plus 4 per cent).
“There is 63 per cent chance of normal, 35 per cent chance of below normal and 2 per cent chance of drought. Cumulative rainfall for August and September is forecast at 92 per cent and 112 per cent (error margin of plus/ minus 9 per cent) of their monthly LPAs, respectively,” said Skymet CEO Jatin Singh.
Earlier, Skymet had predicted “above normal” rainfall (104 per cent) for July and “normal” rainfall in August (99 per cent) and September (96 per cent).
The India Meteorological Department has predicted 88 per cent rainfall, which would mean a “deficient” monsoon. Its July and August forecast stands at minus 8 (92 per cent of the LPA) and minus 10 per cent (90 per cent of the LPA), respectively.
The MeT department is yet to calculate the overall figure for July, but until early this week, it stood at around minus 17 per cent.
The IMD chief had said that the figure was expected to improve as a depression over Rajasthan and Gujarat and cyclone ‘Komen’ were set to trigger rainfall.
The Skymet CEO said that the Madden-Julian Oscillation (MJO) helped rainfall in June. But after June 28, it went to a record negative phase, inducing multiple typhoons in the West Pacific and stealing moisture away from the Indian Ocean.
“MJO is currently erratic. We may conclude two things — MJO might not affect August rainfall adversely and might be favourable in September,” Singh said.
MJO is an oceanic-atmospheric phenomenon which affects weather activities across the globe. It brings major fluctuation in tropical weather on weekly to monthly timescales.
“El Niu00f1o is strong and we have factored this into our forecast. An El Niu00f1o episode correlates well with deficient rainfall in north and north-west India and normal/above normal rainfall in peninsular India. 2015 is peculiar, as the situation is reversed.
“The Indian Ocean Dipole (IOD) is presently neutral and is on track to becoming positive in August. This is favourable for the monsoon,” added Singh.
IOD is defined by the difference in the sea surface temperature between the two equatorial areas of the Indian Ocean -u2013 a western pole near the Arabian Sea (in western Indian Ocean) and an eastern pole closer to the Bay of Bengal (in eastern Indian Ocean). It affects the climate of Southeast Asia, Australia and other countries that surround the Indian Ocean Basin.
The Indian monsoon is invariably influenced by the IOD.