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Capital just 30mm rainfall away from eclipsing all-time record

Since January 1, the Safdarjung weather station – representative of weather records for the city – has recorded 1,502.8mm of rain. In a typical year, Delhi gets 779mm, which means 2021 has brought the city close to twice the amount of rain as a normal year
A large chunk of the rainfall seen this year has come in the monsoon period. Between June 1 and September 30 (the period officially classified as monsoon), the city got 1,169.7mm of rainfall -- an excess of 80% over the long-period average of 648.9mm. (PTI File)
Updated on Oct 26, 2021 04:30 AM IST
ByJasjeev Gandhiok

Sunday’s sudden downpour dumped 27.5mm of rain in Delhi, taking the volume of rain recorded in the Capital this year to beyond 1,500mm for the first time since 1933 — and only a little over 30mm shy of the all-time record.

Since January 1, the Safdarjung weather station – representative of weather records for the city – has recorded 1,502.8mm of rain. In a typical year, Delhi gets 779mm, which means 2021 has brought the city close to twice the amount of rain as a normal year. The year 1933 is when the city received the most rain over a year at 1,534.3mm.

Experts say one or two spells of ‘moderate’ rainfall due to La Nina conditions in the next two months could not only see this record tumble, but bring a harsher, colder winter as well.

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A large chunk of the rainfall seen this year has come in the monsoon period. Between June 1 and September 30 (the period officially classified as monsoon), the city got 1,169.7mm of rainfall -- an excess of 80% over the long-period average of 648.9mm.

R.K Jenamani, scientist at the India Meteorological Department (IMD) said a combination of factors, such as the impact of cyclones, unusually high number of western disturbances and active weather systems from both the Bay of Bengal and the Arabian Sea played a part. “The onset of the monsoon was delayed, but it soon made up the lost deficit. Active weather systems across northern India largely brought excess rainfall from July until September and despite the withdrawal of the monsoon, we have seen more than normal rainfall in October,” said Jenamani.

IMD’s data shows the distribution of rain has also largely been uneven across the year. While July recorded 507.1mm– an excess of 141%, September recorded 413.3mm, an excess of 230%. These two months account for nearly 79% of the total monsoon rainfall and 61% of the annual rainfall so far.

The IMD data also shows instances of ‘heavy’ to ‘very heavy’ rainfall has also been high this year, bringing a large amount of rainfall to Delhi over a short period of time. Delhi recorded seven ‘heavy’ rainfall days in the monsoon period alone, while it recorded one such day in May and October.

The impact of cyclone Tauktae saw Delhi record its highest 24-hour rainfall figure of 119.3mm for May on May 19. Though June did not witness any heavy rain days, July saw three.

The first heavy rain day of the season was recorded on July 19 when Safdarjung received 69.6mm rainfall. The city touched 100mm rainfall on July 27 and the third heavy rain day of the month was recorded on July 30 at 72mm rainfall – all three spells occurring in a short period of three hours or less.

August recorded one ‘very heavy’ rain day when Safdarjung received 138.8mm on August 21, triggering widespread waterlogging.

September saw two back-to-back heavy rain days on September 1 and 2, when 112.1mm and 117.7mm of rain were recorded.

Mahesh Palawat, vice president at Skymet Weather, a private forecasting agency, said there has been an unusually high number of active weather systems reaching Delhi, which has not been seen in the past few years.

“In September, three active weather systems were able to reach Delhi from the Bay of Bengal, which generally seem to fizzle out and lose moisture by the time they reach central India. Similarly, Delhi rarely sees an impact of cyclones, but Tauktae was able to reach up to Delhi and bring the highest 24-hour rainfall for the month. The weekend’s heavy rainfall spell was triggered by westerly winds and moisture coming from both the Arabian sea and the Bay of Bengal, which is unnatural for this time of the year,” said Palawat, stating that while long-term data may be needed to assess these extreme weather events, they indicate a possible impact of climate change too.

If forecasts are to be believed, this erratic trend of rainfall could continue over the next two months as well, with La Nina conditions expected to bring a harsher winter, a report in Bloomberg said.

A moderate to heavy spell of rain this monsoon can generally bring about a sharp drop in day-time temperature. The past weekend’s heavy rainfall spell saw Delhi’s maximum temperature drop to just 23.9 degrees Celsius – nine notches below normal. In May, the impact of Tauktae saw the maximum plummet to sixteen degrees below normal to settle at 23.9°C.

Palawat added that La Nina conditions could bring heavier snowfall in the winter months and similar spells of intense rain in the plains, followed by low temperatures. “La Nina is generally associated with a colder, harsher winter. Based on that, it is possible western disturbances will be more intense in the coming months and there is a good possibility Delhi will receive over 30mm of rainfall in the next two months, to break the all-time annual record.”

IMD data shows so far, this is the fourth wettest October, behind only the years 1954 (238.2mm), 1956 (236.2mm) and 1910 (185.9mm).

Officials said no rain is now expected until the end of the month. The normal rainfall mark for Safdarjung for November is 5.6mm, and for December 9mm.

Last year, Delhi only received a combined 2.2mm between October 1 and December 31.

IMD data since 2015 also shows Delhi has only crossed the annual rainfall mark of 779mm twice – once in 2020 -- Delhi received 1008.6mm that year -- and in 2018, when it received 819.1mm. In 2016, it received a mere 584.3mm.

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