GUWAHATI, April 25 – Quantitatively, the monsoon seasonal rainfall in India during 2015 is likely to be 93 per cent of the Long Period Average (LPA) with a model error of plus-minus five per cent, the India Meteorological Department (IMD) stated in a statement.
The LPA of the seasonal rainfall over the country as a whole for the period 1951-2000 is 89 cm, it said.
The five category probability forecast for the seasonal rainfall during June to September over the country for the current year has also been made by the IMD. It said that less than 90 per cent rainfall range of the LPA has a forecast probability of 33 per cent and a climatological probability of 16 per cent, whereas, below normal rainfall range of the LPA between 90 per cent and 96 per cent has the forecast probability of 35 per cent and a climatological probability of 17 per cent.
The normal rainfall range of 96 to 104 per cent of the LPA has a forecast probability of 28 per cent and a climatological probability of 33 per cent, while the above normal rainfall range of 104 to 110 per cent of the LPA has a forecast probability of 3 per cent and a climatological probability of 16 per cent and the excess rainfall range of above 110 per cent of the LPA has a forecast probability of one per cent and a climatological probability of 17 per cent, said the IMD in its press release.
As the extreme sea surface temperature conditions over the Pacific and Indian Oceans, particularly the El Nino Southern Oscillation (ENSO) conditions over Pacific (El Nino or La Nina) are known to have strong influence on the Indian summer monsoon, IMD is carefully monitoring the sea surface conditions over the Pacific and Indian oceans, it said.
Giving the present picture of the sea surface temperature (SST) for the last about six months, it said 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 and the Pune-based Indian Institute of Tropical Meteorology (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 the Indian Ocean. The latest forecast from the IMD-IITM coupled model indicates negative IOD conditions are likely to persist during the monsoon season.
It may be pertinent to add here that a negative IOD period is characterised by warmer than normal water in the tropical eastern Indian Ocean and cooler than normal water in the tropical western Indian Ocean. A negative IOD SST pattern is believed to be associated with an increase in rainfall over parts of southern Australia.