Mumbai over 3,000mm of rain this monsoon | Mumbai news - Hindustan Times
close_game
close_game

Mumbai over 3,000mm of rain this monsoon

ByPrayag Arora-Desai, Mumbai
Sep 30, 2021 10:36 PM IST

With the official southwest monsoon period ending on Thursday, Mumbai received over 3,000mm of rainfall in the fourth months between June 1 and September. This is 957.7mm more than the seasonal normal of 2205mm, or 30.27 percent departure from the long-period average.

With the official southwest monsoon period ending on Thursday, Mumbai received over 3,000mm of rainfall in the fourth months between June 1 and September. This is 957.7mm more than the seasonal normal of 2205mm, or 30.27 percent departure from the long-period average.

The 2021 monsoon season also marks the third consecutive year in which Mumbai received over 3000mm of rain, and follows 2020’s seasonal total of 3,759.7mm (which was just 70mm short of being the wettest September on record), as per the met department’s monitoring station in Santacruz. (Satish Bate/HT PHOTO)
The 2021 monsoon season also marks the third consecutive year in which Mumbai received over 3000mm of rain, and follows 2020’s seasonal total of 3,759.7mm (which was just 70mm short of being the wettest September on record), as per the met department’s monitoring station in Santacruz. (Satish Bate/HT PHOTO)

The 2021 monsoon season also marks the third consecutive year in which Mumbai received over 3000mm of rain, and follows 2020’s seasonal total of 3,759.7mm (which was just 70mm short of being the wettest September on record), as per the met department’s monitoring station in Santacruz.

Hindustan Times - your fastest source for breaking news! Read now.

In September alone, Mumbai recorded 741.7mm of rain (as against the normal of 341.mm) making it the third-wettest September in a decade. While the average daily rainfall during the month ranged between 40mm and 60mm, a 100mm downpour occurred in the 24-hours ending 8:30am on September 29, making a significant contribution to the monthly total.

August was the only month this season which recorded below normal rain, seeing a negative 46% deficit at the end of the month. The highest rainfall recorded was 78.44mm of rain in the nine hours ending 5:30pm on August 31, categorised as ‘heavy rain’ by the IMD. The total amount of rainfall received until 8:30 am on August 31 stood at 338.8mm (against the monthly normal of 531.3mm), making it the fourth-driest August in a decade as per IMD records. This follows last year’s above normal reading, when August recorded a whopping 1,247.7mm of rain.

This year, the city saw three ‘extremely heavy’ rainfall days (one in June and two in July), receiving over 204.5mm in 24-hours. The first of these events occurred on June 10 (231.3mm), coinciding with the arrival of the south-west monsoon two days prior to the official onset date of June 11. On the day, Mumbai received 220.6mm rain of between 8.30am and 5.30pm, or 43.6% of the monthly normal in just nine hours. The city witnessed a total of 961.4 mm of rainfall for the month (against the normal of 505mm), making it the third-wettest June in the last decade.

The highest amount of rain -- 1222mm -- was received in July. The month also saw two consecutive, atypical thunderstorms which dumped more than 500mm rain over the city, resulting in the second and third ‘extremely heavy rainfall’ events of the season. A convective thunderstorm, described by meteorologists as “monstrous”, deposited a whopping 235mm rain between 12am and 4am on July 18, less than 48 hours after a similar high rainfall event resulted in the season’s highest daily rainfall on July 16 at 253mm. July rains saw a 48% departure from the monthly normal of 822mm.

Officials in the India Meteorological Department (IMD), including KS Hosalikar (scientist, surface instrument division), did not offer any comments on this year’s monsoon, stating that all notable features will be covered in an upcoming monsoon report by the IMD which is expected within the next day or so. Experts, however, pointed out that despite receiving excess rains, this past season has been marked by very significant “intraseasonal variability” -- a phenomenon which bears a clear signature of climate change.

“In terms of high-impact rainfall events in Mumbai-MMR, the second half of the southwest monsoon season has been relatively quiet than the first one. Across India, we have witnessed a very strong intraseasonal rainfall variability between August (sixth driest since 1901) and a very wet September (tenth wettest since 1901), a pattern which is projected to become more robust due to climate change. Such a strong intraseasonal rainfall variability rainfall has a lot of implications for agriculture and flood risk mitigation. Another peculiar feature of the 2021 monsoon is that we got only a single low-pressure system (LPS) in June, 3 in July, 2 in August, but 6 in September. The increased LPS frequency in September did not actually translate to heavy rainfall events in Mumbai, so there’s definitely a lot to investigate meteorologically,” said Akshay Deoras, an independent meteorologist and a PhD candidate at the University of Reading, UK.” A senior meteorologist at IIT-M in Pune, seeking anonymity, said that despite receiving excess rains for three years in a row, monsoon patterns over the Konkan (as with the rest of India) are now showing intermittent dry periods with short spells of heavy rains within the monsoon season, and that the number of extreme rainfall events have increased by at least three times over the city. “This also poses a huge challenge to forecasting, because the IMD and our models are not able to predict such intense bursts early enough. So the time for evacuating vulnerable populations also becomes very less. This year’s monsoon is in keeping with trends that are going to significantly exacerbate climate risk in the foreseeable future,” the scientist said.

SHARE THIS ARTICLE ON
Share this article
SHARE
Story Saved
Live Score
Saved Articles
Following
My Reads
Sign out
New Delhi 0C
Thursday, February 22, 2024
Start 14 Days Free Trial Subscribe Now
Follow Us On