The Indian Dipole is another major influence on the outcome of the monsoon. A negative IOD is associated with the heating of the Indian Ocean waters and a positive IOD is linked to the cooling of Indian Ocean waters.
The Southwest monsoon, which brings nearly 75 per cent of rainfall to the country, is expected to be normal this year, the India Meteorological Department (IMD) said on Friday.
The Long Period Average (LPA) will be 98 per cent with an error margin of plus and minus 5 per cent, said M Rajeevan, secretary of the Ministry of Earth Sciences.
Rainfall in Odisha, Jharkhand, eastern Uttar Pradesh, Assam and Meghalaya is likely to be below normal, but normal or above normal in the rest of the country, he said while releasing the first Long Range Forecast for the four-month rainfall period from June to September.
“The monsoon will be 98 per cent of the LPA, which is normal rainfall. It is a really good news for the country and will help India have a good agriculture output,” Rajeevan said at a virtual press conference.
The LPA, the average of the season’s rainfall across the country from 1961-2010, is 88 centimetres.
According to the prediction of the Operational Statistical Ensemble Forecasting System (SEFS), there is a 40 per cent probability of a normal and 16 per cent probability of an above normal rainfall this season. There is a 25 per cent probability of a below normal rainfall, the IMD said.
The news augurs well for the economy, battered due to the coronavirus pandemic. The Southwest monsoon is one of the primary drivers of the country’s economy, which is largely based on agriculture and its allied activities. Large parts of the country rely on the four-month rainfall season for agriculture and also for filling reservoirs.
This is the first time the IMD has made a specific forecast on spatial distribution.
Rajeevan said the IMD will issue month-wise forecasts during the next four months and also for the homogenous regions of the country — the IMD’s four divisions — the Northwest India, East and Northeast India, Central India and South Peninsula.
The country has recorded above normal rainfall for the last two rainfall seasons.
The La Nina and El Nino factors are major influences on the Indian monsoon. The former is associated with the cooling of the Pacific waters and brings good rainfall while the latter is linked to the heating of Pacific waters and could lead to deficient precipitation.
“There are less chances of formation of an El Nino,” Rajeevan said.
He said in the recent years, the year after La Nina has usually seen a normal rainfall season.
The Indian Ocean Dipole (IOD) is another major influence on the outcome of the monsoon. A negative IOD is associated with the heating of the Indian Ocean waters and a positive IOD is linked to the cooling of Indian Ocean waters.
The latest global model forecast indicates that neutral ENSO (El Nino Southern Oscillation) conditions are likely to continue over the equatorial Pacific and negative IOD conditions are likely to develop over the Indian Ocean during the ensuing monsoon season, IMD Director General M Mohapatra said.
“La-Nina is favoured through March-May with 80 per cent chances of a transition to ENSO-neutral in April-June 2021 and continuing through the fall of 2021,” Rajeevan said, implying these conditions are favourable for a good rainfall season.
Earlier this week, Skymet Weather, a private weather forecasting agency, had also predicted a normal monsoon. However, it had pegged the precipitation during the four-month season at 103 per cent of the LPA, which is on the higher side.
Precipitation in the range of 96-104 per cent is considered to be in the ‘normal category’.
The Skymet had said the north India plains, along with a few parts of the northeast region, are likely to be at a risk of being rain deficient through the season. Also, interior parts of Karnataka face the scare of scanty rains in the core monsoon months of July and August.
On a monthly scale, June is likely to receive rainfall of 106 per cent of LPA, while July is expected to record 97 per cent of LPA. August and September are expected to receive 99 per cent and 116 per cent of the LPA, the Skymet said.