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Private forecaster Skymet sees ‘healthy normal’ monsoon this year

Vinson Kurian Thiruvananthapuram | Updated on April 13, 2021

Assessed at 103% of long-period average; drought ruled out

Private forecaster Skymet Weather expects the upcoming monsoon to be ‘healthy normal’ assessed at 103 per cent (with an error margin of +/- 5 per cent) of the long-period average (LPA) of 880.6 mm for the June-September period. If Skymet is proved right, it will be the third normal South-West monsoon on a trot the country will have.

 

The national forecaster, India Meteorological Department (IMD), is expected to come up with its own long-range forecast for the four-month season soon.

Monsoon probabilities

According to Skymet, the monsoon probability for June-July-August-September are: 10 per cent chance of excess (seasonal rainfall that is more than 110 per cent of LPA); 15 per cent chance of above normal (between 105 per cent and  110 per cent); 60 per cent chance of normal (96-104 per cent); 15 per cent chance of below normal (90-95 per cent); and practically zero per cent chance of drought (seasonal rainfall that is less than 90 per cent of LPA).

 

On a monthly scale, the precipitation foreshadow is as follows:

  June: 106 per cent of LPA (LPA for June - 166.9 mm); 70 per cent chance of normal; 20 per cent chance of above normal; and 10 per cent chance of below normal.

 July: 97 per cent of LPA (LPA for July - 285.3 mm); 75 per cent chance of normal; 10 per cent chance of above normal; 15 per cent chance of below normal.

 August: 99 per cent of LPA (LPA for August - 258.2 mm); 80 per cent chance of normal; 10 per cent chance of above normal; 10 per cent chance of below normal.

 September: 116 per cent of LPA (LPA for September - 170.2 mm); 30 per cent chance of normal; 60 per cent chance of above normal; 10 per cent chance of below normal.

Earlier preliminary forecast released by Skymet on January 31 had assessed the monsoon 2021 to be ‘normal’ with seasonal rainfall ending in the upper half of the normal range, with the spread of normal rainfall being 96-104 per cent of LPA.

In terms of geographical risk, Skymet expects that the plains of North India along with some parts of North-East India to be at risk of being rain deficient through the season. Also, interior parts of Karnataka face scare or scanty rains in the core monsoon months of July and August.

Good June, Sept months

The onset month of June and the withdrawal phase of September promise good countrywide rainfall distribution. Yogesh Patil, CEO, Skymet, said that La Nina conditions prevailing in the Pacific Ocean since last year presage some softening and may remain neutral through the monsoon season.

The tropical Pacific conditions continue to wield a spike mid-way through the season suggesting fresh phase of cooling, albeit marginal, over the Central Pacific Ocean.

El Nino ruled out

The Indian Ocean Dipole (IOD) is neutral and is oscillating lightly on either side of the zero line. This parameter seems to incline with a negative shift but remaining within the threshold limits. In this case, it may not heave the monsoon spurts but will refrain from harming the season.

The Madden Julian Oscillation (MJO) wave, the equatorial wave that passes over the Indian Ocean periodically, is currently sailing far away from the Indian Ocean. It barely makes three or four visits during the entire season. It is too early to comment on its impact on the monsoon just yet.

Published on April 13, 2021

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