Rainfall during August and September likely to be on higher side of normal: IMD

PTI, Aug 2, 2021, 2:42 PM IST

New Delhi: Rainfall during August and September, the second half of the four-month rainfall season, is likely to be on the higher side of normal, the India Meteorological Department (IMD) said on Monday.

In another forecast for August, IMD Director General Mrutunjay Mohapatra said monsoon is also likely to be normal in the month.

“The 2021 August to September rainfall averaged over the country as a whole is most likely to be normal (95 to 105 per cent of Long Period Average) with a tendency to be on the positive side of the normal,” Mohapatra said at an online briefing.

The LPA of the August to September period rainfall over the country as a whole for the years 1961-2010 is 428.3 mm.

Every year, the IMD issues forecast for the second half of the Southwest Monsoon, for August and September, the last two months of the four-month rainfall season.

The spatial distribution suggests that below normal to normal rainfall is likely over many parts of the north, east and northeast parts of the country. Normal to above normal rainfall is most likely to be experienced over most parts of peninsular India and adjacent central India, the IMD said.

The IMD has also started issuing month-wise forecast for the four-month rainfall season from this year.

For August, it said, “Rainfall averaged over the country as a whole is most likely to be normal (94 to 106 per cent of LPA),” Mohapatra said.

The LPA of the August rainfall over the country as a whole for the period 1961-2010 is 258.1 mm

The spatial distribution suggests that below normal to normal rainfall is likely over many areas of central India and some areas over north India.

“Normal to above normal rainfall is most likely over most parts of peninsular India and northeast India” he added.

Mohapatra added that currently the Sea Surface Temperatures (SSTs) and the atmospheric conditions over the equatorial Pacific Ocean indicate neutral ENSO (El Nino) conditions.

The SSTs is one of the major factors that influence the Indian monsoon. The SSTs over central and east equatorial Pacific Ocean are showing cooling tendency.

The latest forecasts suggests that ENSO neutral conditions are likely to continue during the remaining part of the monsoon season and increased possibility of re-emergence of the La Nina conditions in the end of the monsoon season or thereafter.

La Nina is associated with the cooling of the Pacific Ocean waters, while El Nino is linked to its heating.

In addition to ENSO conditions over the Pacific, other factors such as the Indian Ocean SSTs also an influence on Indian monsoon. Currently, the negative Indian Ocean Dipole (IOD) conditions are prevailing over the equatorial Indian Ocean.

Forecasts indicate that negative IOD conditions are likely to continue during the remaining part of the monsoon season.

A negative IOD is associated with the heating of the Indian Ocean waters, while a positive IOD is linked to its cooling. Positive IOD conditions are conducive for a good rainfall season.