Weak El Nino conditions but timely monsoon still expected

El Nino conditions can suppress the Indian southwest monsoon. Weak El Nino conditions exist for the second year running but the IMD’s forecast is for the monsoon to hit the mainland at Kerala on 30th May ± 4 days.

Whenever an El Nino is about, the doomsayers compete with catastrophe scenarios, but the possibility of a “bad” monsoon in 2015 is diminishing.The economic and industrial recovery should not be adversely affected to any great extent.

Forecasts for the last nine years (2005 to 2014) were as in the table below.

Monsoon onset dates.emf

A timely monsoon (onset during May) does not necessarily mean a “good” monsoon during the official 4 months (June to September) of the season, but does decrease the probability of a “bad” monsoon. The pre-monsoon rains during May have been somewhat higher than normal but not uniformly across the country. Rainfall at the wrong time is not that useful of course but early rainfall in May and late rainfall in October does still have value.

IMD ForecastFor the last about six months, positive SST anomalies have been prevailing over the western and the central Pacific Ocean. However, the SSTs over eastern Pacific after remaining near to below normal between late December 2014 and mid-March 2015 have now become above normal. Thus currently, weak El Nino conditions are prevailing over the Pacific.

The latest forecast from the IMD-IITM coupled model forecast indicates El Nino conditions are likely to persist during the southwest monsoon season.

At present, slight negative Indian Ocean Dipole (IOD) conditions are prevailing over Indian Ocean. The latest forecast from the coupled model indicates negative IOD conditions are likely to persist during the monsoon season. ……. the extreme sea surface temperature conditions over Pacific and Indian Oceans particularly ENSO conditions over Pacific (El Nino or La Nina) are known to have strong influence on the Indian summer monsoon.

 Quantitatively, the monsoon seasonal rainfall is likely to be 93% of the Long Period Average (LPA) with a model error of ± 5%. The LPA of the season rainfall over the country as a whole for the period 1951-2000 is 89 cm.

It is early days yet, but currently the advancing monsoon front is past the Andamans and slightly ahead of the long term average.

Monsoon front May 2015 IMD

Monsoon front May 2015 IMD


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