India Meteorological Department: End of Season Report for the 2018 Southwest Monsoon

Situation Report
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  • The season (June-September) rainfall over the country as a whole was 91% of its long period average (LPA).

  • Seasonal rainfalls over Northwest India, Central India, South Peninsula and Northeast (NE) India were 98%, 93%, 98% and 76% of respective LPA.

  • Out of the total 36 meteorological subdivisions, 23 subdivisions constituting 68% of the total area of the country received normal season rainfall, 1 subdivision received excess rainfall (1% of the total area), and 12 subdivisions (31% of the total area) received deficient season rainfall.

  • Monthly rainfall over the country as a whole was 95% of LPA in June, 94% of LPA in July, 92% of LPA in August, and 76% of LPA in September.

  • Southwest monsoon current reached south Andaman Sea and Nicobar Islands on 25th May (5 days later than its normal date), but further advance was relatively faster. It set in over Kerala on 29th May, 3 days ahead of its normal date, thereafter progressed rapidly and covered the entire country in one month (on 28th June) well ahead of its normal schedule. Monsoon withdrawal commenced from west Rajasthan on 29th September (with a long delay of almost one month). However further withdrawal was very rapid as the monsoon withdrew from most parts of northwest India and adjoining central India by 1st October and from major parts of the country outside southern parts of Peninsula by 6th October. Rainfall activity continued over south peninsula due to the presence of an active Inter Tropical Convergence Zone (ITCZ) with embedded easterly wave perturbations. Subsequent to the equator ward shifting of the ITCZ and reduction in rainfall, the southwest monsoon withdrew from the entire country, Bay of Bengal and the Arabian Sea on 21st October 2018, with a delay of 6 days.

  • During the season, 10 monsoon low pressure systems (1 cyclone, 1 Deep Depression, 4 Depressions, 2 well marked low pressure areas & 2 low pressure areas) formed against an average of 6 Depressions & 8 low pressure areas.

  • Forecast for monsoon onset over Kerala for this year was very accurate, as both the forecasted and realized date of onset of monsoon over Kerala was 29th May.

  • Forecasts for the seasonal rainfalls over three broad geographical regions (NW India,
    Central India and South Peninsula) and that for July and August rainfall over the country as a whole were correct. However, the forecasts for the rainfall over the country as a whole during the season and second half of the monsoon season and forecast for North-East India were overestimates to the actual rainfall.