Mumbai records its wettest July, breaks all-time high monthly rain record
On Tuesday, south Mumbai recorded intermittent intense spells through the day with 83.6 mm (heavy) rain from 8.30 am to 5.30 pm while the suburbs recorded 7.7 mm rain. Over the last 24 hours moderate rain was recorded in the suburbs and south Mumbai.Updated: Jul 28, 2020 21:18 IST
The city surpassed its July 2014 record (1,468.5mm) for the all-time high monthly rainfall on Tuesday with intermittent intense rain spells taking the monthly rain tally to 1,474.3 mm from July 1 to July 28 5.30pm.
On Tuesday, south Mumbai recorded intermittent intense spells through the day with 83.6 mm (heavy) rain from 8.30 am to 5.30 pm while the suburbs recorded 7.7 mm rain. Over the last 24 hours moderate rain was recorded in the suburbs and south Mumbai.
A yellow alert (heavy rain warning) was issued for Wednesday and Saturday by the weather bureau.
Read latest updates on Mumbai rains here.
Meanwhile, the city had surpassed its July average rain target of 840 mm in the first 15 days itself, and has currently recorded 75.5% excess rain for the month. Mumbai has witnessed a total of eight heavy to very heavy rain days this month, which paved the way for previous records to be broken.
The India Meteorological Department (IMD) maintains rain data from 1959 onwards. Though Mumbai received 944.2 mm rain during July 2005, the monthly total was 1454.5 mm. Last year, the city had recorded 1,464.8 mm rain during July. Other landmark years over the past 61 years include 1,455.5 mm in 1965, 1,385.5 mm in 1961, 1,312.9 in 2011, 1,250.4 in 2010, and 1,226.1 mm in 1988.
IMD classifies 15.6-64.4 mm as moderate rain while 64.5-115.5 mm rain as heavy, 115.6-204.4 mm as very heavy, and over 204.5 mm as extremely heavy rain for a period of 24-hours. The city witnessed five ‘very heavy’ rain days through the month so far with maximum rain recorded between July 4 and 5 at 200.8 mm followed by 191.2 mm on July 15-16. Additionally three ‘heavy’ rain days. Apart from July 2, the city has received rainfall every day of the month.
IMD officials said rain during July was consistent as opposed to the pattern during June. Mumbai witnessed a deficient rain during June with the lowest rainfall in five years as the city fell 98 mm short of its monthly average target. “Weather systems in the Arabian Sea and larger factors such as a weak positive Indian Ocean Dipole (IOD) - an ocean-atmosphere phenomenon with difference in sea surface temperatures characterised by cooling in parts of Indian Ocean leading to enhanced rain - ensured active monsoon conditions through most of the month allowing westerly winds to bring in a lot of moisture over the city,” said a senior IMD official.
Professor Sridhar Balasubramanian, department of mechanical engineering and IDP Climate Studies, Indian Institute of Technology, Bombay said weather synoptic conditions were more active in Arabian Sea than Bay of Bengal, resulting in good rains over Mumbai during July. “Positive IOD indicates a warm pool of water in the west Arabian Sea (near Somalia). This is good for bringing moisture over to the west coast. The favorable IOD was witnessed last year as well. The presence of a moderate to strong offshore trough throughout July ensured steady and consistent rains breaking an all-time record,” he said.
Thundershowers were reported on at least 15 days in July as against the normal of three days for Mumbai, said Akshay Deoras, independent meteorologist and PhD researcher at the University of Reading, United Kingdom. “A preliminary analysis suggests that the number of rainy days in Santacruz this July has been higher than the normal of 23 days. Intense rain on most days occurred after midnight instead of early afternoon. Thus, increased thunderstorm activity seems to have played a major role in enhancing rainfall,” he said.
Though the city received excess rain for the month, showers evaded catchment areas. Even as Tulsi Lake overflowed on Tuesday, water stock across seven lakes supplying water to Mumbai was 32.7% of the required amount. Last year, it was 75% of the required quantum by this period. “
Since catchment areas are located further interior from the coast, cloud bands have not penetrated owing to weak wind drag. However, this is likely to change in August as the Bay of Bengal gets ready to churn a system,” said Balasubramanian adding, “The city could expect above normal rain for August.”
Mumbai has so far received 82.6% of its seasonal average rainfall from June 1 to July 28.