On 15 April 2019, IMD released its Long Range Forecast of the Southwest Monsoon Season. Quantitatively the seasonal rainfall was predicted at 96% of the Long Period Average (LPA) with a model error of +/- 5%. The LPA for the country as a whole is 887mm for the four months-long monsoon season from June to September. On 31 May 2019, in its Long Range Forecast update for the season, IMD retained its earlier forecast of 96% and now with a model error of +/- 4%.
Also in this update, July and August rainfall was predicted to be 95% and 99% of LPA respectively. The latest Long Range Forecast for the second half of the season, implying August and September has been estimated at 100% of LPA. Rainfall during August as such is forecast at 99%. Also, it is stated that the accrued rain deficit of 9% so far will also get recovered.
Monsoon rains this season had started on a sluggish note and the month of June ended with a large deficit of 33%. Thereafter active monsoon conditions prevailed for over two weeks in July. Accordingly, the shortfall got reduced to 9 %, amounting to 42mm of rainfall.
Reading in between the lines of the second stage monsoon forecast implies the following:
* The forecast 100% rainfall during the second half along with conditional 99% in August implies that rainfall during September needs to be 102% of LPA.
* Merely 100% of rainfall in the second half will not be able to recover the deficiency of 9%. Even in this best possible scenario, the seasonal deficiency will stand at 5% which could possibly lead to a Below Normal Monsoon.
* To recover the complete deficiency of 9%, the second half of season needs to perform at 110% of LPA.
As per Skymet the second half of August is likely to see a slowdown in the monsoon current and thereby find it difficult to score over 100% of LPA. The month of August holds the key for the overall fate of monsoon this season.
Image Credit: NDTV
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