‘Normal’ monsoon in Aug, Sept, says IMD
NEW DELHI: India is likely to receive “normal monsoon rain” in August and September, the second half of the four-month rainfall season, the India Meteorological Department (IMD) said on Monday.
“As per most parameters, we expect monsoon rains to be normal in August and September this year,” Mrutyunjay Mohapatra, director general of the IMD, told reporters on Monday.
Rainfall between 96% -104% of LPA is considered “normal”; between 90% and 96% is considered “below normal” and between 104% and 110% is considered “above normal” by IMD.
“Rainfall averaged over the country as a whole is most likely to be normal (94 to 106 per cent of LPA) in August,” Mohapatra added. The LPA for August from 1961 to 2010 is 258.1mm.
During August and September, “below normal” to “normal” rainfall is likely over many areas of the northwest, east and northeast India while “normal” to “above normal” rainfall is most likely over peninsular India and adjacent central India, IMD said in its monsoon forecast for the second half of the season released on Monday.
In August, “below normal” to “normal” rain is likely over many areas of central India and parts of northwest India while “normal” to “above normal” rain is likely over most parts of peninsular India and northeast India, the IMD added.
July recorded a 7% deficiency in rain, with 26% deficiency over east and northeast India; 27% excess over south peninsula; 7% deficiency over northwest India and 7% deficiency over central India. June ended with 10% excess rain but a monsoon break of around 12 days from June 19 to July 11 led to a long dry spell in many parts of the country. After monsoon revived, extreme rainfall events, floods and landslides in Konkan and Madhya Maharashtra and in Himachal Pradesh and Uttarakhand marked the July monsoon.
There were 567 stations this July which reported “very heavy” rain in July of about 11.56 cm to 20.45 cm; 112 stations reported “extremely heavy” rain of over 20.45cm. In the past 5 years, 2019 saw the highest number of stations reporting extreme rain including 753 stations reporting “very heavy” rain and 161 stations reporting “extremely heavy” rain.
La Niña approaching
IMD flagged that La Niña conditions are gradually likely to set in around September and October and could continue till next
spring (2022). The transition to La Niña conditions has started, which is favourable for monsoon. “We cannot say immediately if it will be a prolonged monsoon, but La Niña conditions support good rains. La Niña years are also linked to higher chances of cyclogenesis over Bay of Bengal in the postmonsoon season in October, November and December,” said Mohapatra.
Sea surface temperatures over central and east equatorial Pacific Ocean is showing a cooling tendency and there is an increased possibility of re-emergence of La Niña conditions in the end of the monsoon season or thereafter, IMD said on Monday. Negative Indian Ocean Dipole (IOD) conditions over Indian Ocean are likely to continue during the monsoon season. “As the changes in the sea surface temperature (SST) conditions over the Pacific and the Indian Oceans are known to influence the Indian monsoon, IMD is carefully monitoring the evolution of sea surface conditions over these ocean basins,” IMD said in a statement.
La Niña, a global meteorological phenomenon, is linked to very cold and harsh winters in India and “above normal” monsoon rains. La Niña is also linked to increased frequency of cyclones over Bay of Bengal. A paper published in International Journal of Meteorology in 2019 on impact of ENSO on the Bay of Bengal tropical cyclone (TC) activity during post-monsoon (October–December) season for a period of 44 years (1972–2015) found that La Niña years are characterized by more frequent and intense cyclonic events compared with El Niño years.
This winter is also likely to be colder than normal this year. “This winter may be colder than normal but its too early to say. We will issue a forecast before the season. Normally, cyclone frequency is also higher in La Niña years,” said OP Sreejith, head, climate monitoring and prediction group, IMD Pune.
A well-marked low pressure area over southeastern parts of West Uttar Pradesh and neighbourhood now lies over southwest Uttar Pradesh and adjoining northwest Madhya Pradesh. It is likely to move westwards gradually during next 3 days. The monsoon trough has shifted slightly north of its normal position. Under the influence of these systems, fairly widespread rainfall with isolated “heavy” to “very heavy” rain is very likely over Madhya Pradesh during August 2 and 6. Isolated “extremely heavy rain” (over 20cm) is also very likely over West Madhya Pradesh on August 2 and 3 with reduction from August 4. Widespread, “heavy” to “very heavy” rainfall is very likely to continue over east Rajasthan till August 6. Current spell of widespread rainfall activity is very likely to continue over rest of north India with isolated “heavy” rain over Uttarakhand and West Uttar Pradesh during the next five days. Isolated “heavy” rain is likely over Haryana during the next three days and Himachal Pradesh on August 4 and 5.