The India Meteorological Department in its ‘Long Range Forecast for the Rainfall during Second Half (August –September) of the Southwest Monsoon 2018’ has said:
(a) The rainfall during August 2018 is likely to be 96 ± 9% of LPA and expected to be higher than was predicted in June.
(b) Quantitatively, the rainfall for the country as a whole during the second half of the season (August and September) is likely to be 95% of LPA with a model error of ±8%.
(c) The tercile probability forecasts for the rainfall over the country as a whole during the 2018 second half of the monsoon season are: 47% forecast probability that it will be less than 94% of the LPA (below normal), 41% forecast probability that it will be between 94% and 106% of the LPA (normal), and only 12% forecast probability that it will be over 106% of the LPA (above normal).
The Department said that “distribution of rainfall is very good over all parts of the country except Bihar, Jharkhand and NE States. Such a scenario of favourable distribution of rainfall is expected to continue during rest of monsoon season of 2018 so as to remain favourable for agricultural operations”.
The IMD in its latest weekly ‘performance sheet’ on rainfall has calculated the cumulative rainfall up to 1 August 2018 on an ‘area weighted’ basis as being 431 mm as compared with a normal of 462 mm. But this is a measure that doesn’t tell us anything local and we have advised the IMD to abandon it. What is more useful is the enumerating of subdivisions according to cumulatie rainfall: by 1 August, there were 28 which had normal rainfall, 7 which had deficient, and one which had excess. For this period – monsoon rainfall until 1 August – this year has had the most number of subdivisions with normal rainfall in the last five years.
However it is a concern that five of the seven subdivisions which up to 1 August 2018 have had deficient rainfall are in the East and North-East India region and they are: Arunachal Pradesh (-36%), Assam and Meghalaya (-33%), NMMT which is Nagaland Manipur Mizoram Tripura (-25%), Jharkhand (-24%) and Bihar (-22%). The other two subdivisions with deficits are Rayalaseema (-41%) and Lakshadweep (-43%).
In states, Uttar Pradesh has the largest number of districts (26) registering deficient rainfall up to 1 August 2018, even though 25 of the state’s districts have had normal rainfall for the period and 18 have had excess or large excess. Bihar has 24 districts which have registered deficient rainfall for this period, followed by Jharkhand (15), Assam (14), and Gujarat, Tamil Nadu and Karnataka each with 13.
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