Drier August, September likely as El Nino intensifies: IMD

The currently weak El Nino condition prevailing currently is expected to intensify further and become moderate during the next two months.

The feared El Nino could put a damper on what has been a surplus (if patchy) monsoon season this far.

August and September together usually account for 46% of monsoon rain) (Vijay Bate/HT Photo)

Monsoon rain over the country during the second half of monsoon season is expected to be on the lower side of the “normal” category, ranging between 94% and 99% of the long period average or the average of the rainfall between 1971 and 2020. Rainfall during August itself is likely to be “below normal” ranging between 90% and 94% of LPA, the India Meteorological Department (IMD) said on Monday. August and September together usually account for 46% of monsoon rain.

The weak El Nino condition prevailing currently is expected to intensify further and become moderate during the next two months, affecting monsoon rainfall in the remainder of a season, meteorologists said.

During August and September, normal to above normal rainfall is likely over most parts India adjacent to/along the Himalayas, east central India, and some parts of east and northeast India. But below normal rainfall is likely over most parts of peninsular India, and parts of northwest and central India. LPA of the rainfall over the country as a whole for August and September based on the data of 1971-2020 is 42.8 cm and for August alone it is 25.5 cm.

“We are saying that rainfall during next couple of months is expected to be normal but on the lower side of normal and rain is expected to below normal during August. This means that there may be more rain in September. But the picture for September will be clearer next month. We are expecting El Nino conditions to intensify and at the same time there is likely to be positive Indian Ocean Dipole conditions. The atmosphere did not respond to warm ocean temperatures or El Nino conditions so far. But we may see its impact going forward,” said M Mohapatra, director general, IMD.

During August, above normal maximum temperatures are likely over most parts of south Peninsula, east and northeast India, and many areas of northwest and central India. Normal to below normal maximum temperatures are most likely over some areas of north peninsular India, east central India and along the plains of Himalayas. Minimum temperatures are also likely to be above normal over most parts of India except some parts of northwest India which will see below normal minimum temperatures. .

“The rainfall averaged over the country as a whole during second half of the monsoon season (August – September) is most likely to be normal (94-106% of LPA), with a tendency to be on negative side of the normal,” IMD said in a statement adding that rainfall over the country as a whole during August 2023 is very likely to be below normal (<94% of LPA).”

“The latest extended range forecast from a couple of leading climate prediction centres suggest monsoon is entering into weak phase during first week of August and then classic break condition during the second week. There is a suggestion that it may extend into the third week also but there could be uncertainties,” M Rajeevan, former secretary, ministry of earth sciences said on July 26.

“This break is inevitable after a long active monsoon spell. We need not still panic but closely monitor the situation,” added Rajeevan.

El Nino has a strong influence on the southwest monsoon in India. El Nino is characterised by an unusual warming of waters in the eastern equatorial Pacific, which has a high correlation with warmer summers and weaker monsoon rains in India. Positive IOD on the other hand is good for southwest monsoon over India. IOD refers to the temperature differential between the western and eastern Indian Oceans. A positive IOD has a direct correlation with a good monsoon

An unusual July marked by extreme events

Thus far, since the start of the monsoon (June 1), there has been 5% excess rainfall over the country with 31% excess over northwest India; 12% excess over central India; 5% excess over peninsular India and 25% deficiency over east and northeast India. In July alone, there was 13% excess rain over the country; 25% excess over northwest India; 32% deficiency over east and northeast India; 22% excess over central India and 45% excess over the southern peninsula.

IMD’s data indicates that July was marked by extreme rainfall event in different parts of the country. Incidence of heavy rain (11.56 cm to 20.45 cm) and extremely heavy rainfall (more than 20 cm) were the highest this July since 2019. There were 205 events of extremely heavy rain and 1113 events of heavy rainfall last month. There were several events of exceptionally heavy rain (over 25 cm and nearing historical record) last month. For example, Chandigarh recorded 30 cm rain on July 9; Sutrapada in Saurashtra recorded 54 cm on July 18; Laxmidevipeta in Telangana recorded 65 cm on July 27; Raigad in Konkan recorded 40 cm on July 20 . Several stations including Chandigarh and Ambala saw records in July. Delhi’s Safdarjung also recorded the third highest rainfall for a 24 hour period on July 8 to 9, 15.3cm.

Average mean temperature during July was the eighth warmest and minimum temperature was the second warmest in July since 1901. “This can be attributed to clouding during July which leads to warmer nights as the heat cannot escape,” said Mohapatra. East and northeast India recorded the warmest minimum temperatures since 1901 and the region also recorded third lowest rainfall for July since 1901. Four low pressure areas formed which helped good rainfall, western disturbances also helped bring rain to north India.

During IMD’s presentation, Mohapatra added that there is a consistent rise in mean and minimum temperature over the country since 1990s. “This can be seen as an imprint of climate change,” he added.

HT reported on July 30 that there is major deficiency of rainfall over the paddy growing Indo-Gangetic plains area and parts of northeast India in July.