Battered by one of the worst floods in decades, Northwest India recorded its wettest July in 23 years with average monthly rainfall of 258.6 mm, said the India Meteorological Department (IMD). However, the rainfall is now likely to be below-normal in August, as monsoon braces to enter a subdued phase.
The southwest monsoon arrived late but covered the country earlier than usual and gained tremendous momentum in July. Record-breaking rains lashed several regions with extremely heavy rains exceeding 205.mm in as many as 205 meteorological stations – maximum in the last five years.
However, the rainfall over Northwest India was the highest since 2001. Chandigarh and Ambala (Haryana) saw all-time high rains on July 9, with 302mm in Chandigarh and 224.1mm in Ambala, leading to massive deluge. An extremely heavy spell of rain impacted Gujarat, Maharashtra, Goa and Karnataka from July 18 to 28.
WHAT LED TO THE HEAVY RAINS
“If you view it in the backdrop of climate change, then definitely there has been an overall increase in the frequency of very heavy rainfall events. There was intense western disturbance activity, and as many as four low pressure systems in Bay of Bengal in July against the normal of three,” said India Meteorological Department (IMD) chief M Mohapatra.
Meteorologists say it was the confluence of active monsoon conditions, four western disturbances and four low pressure systems that led to torrential rains throughout the month. However, the most intense western disturbance impacted the northern region from July 5 to 11 that triggered one of the worst floods in Northwest India when it interacted with a vigorous monsoon.
The convection was further bolstered by monsoon trough which remained south of its normal position on many days favouring rainfall over central and peninsular India. Another system – the Madden Julian Oscillation (MJO) — was also in a favourable phase on many days.
SUBDUED RAINS IN AUGUST
However, after intense activity, the weather department has predicted a normal monsoon for the last two months of the season, with rains likely to be below normal in August and picking up in September. The opposing impact of El Nino, which was not visible during July, is also expected to influence the monsoon circulation in August with rains at 94% of LPA.
“Though El Nino is associated with subpar rains, this time it was not able to influence the monsoon circulation that much. The atmosphere did not respond to the warm ocean temperatures which basically signal formation of El Nino. However, there is a 90% probability that the ocean phenomenon will now get stronger,” added Mohapatra.
According to the forecast, rainfall along the foothills of the Himalayas, including northern parts of Uttar Pradesh and Bihar, are likely to be normal to above normal rains, the activity would be subdued over western parts of northwest India, peninsular states and central India.
NIGHT TEMPERATURE SECOND WARMEST SINCE 1901
While the global temperature rise breached all records this month, IMD highlighted that it was not the warmest July for India. However, the night time temperatures were the warmest-ever for east and northeast India in almost 100 years. The region also recorded a staggering rainfall deficit with a subpar monsoon.
For the country as a whole, the minimum temperatures were the second warmest-ever since 1901.
As of August 1, the monsoon rains are now in excess of 5% across the country, improving largely from the nearly 10% rainfall deficit in June. While Northwest India has witnessed 31% excess rains during the monsoon season, it stands at 12% for Central India and 5% for peninsular states. However, north-eastern India still faces a deficit of about 25%, with the third lowest July rainfall since 1901.
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