Mumbai, its satellite cities, along with north and central Maharashtra, received unseasonal rainfall in the first few days of December, marking a disruption in the usual weather pattern of the region.
The maximum temperature observed in Mumbai on 1 December plummeted to 24 degrees Celsius – eight degrees below the normal – after the untimely showers, as per the Indian Meteorological Department (IMD). This is the second-lowest temperature in Mumbai for December in a decade.
"We sometimes do see rainfall in December in this region, but this year it was record breaking," said Anupam Kashyapi, Head of Weather Forecasting Division for IMD, Pune.
Talking about the weather abnormality, AVM (Rtrd) GP Sharma, President of Meteorology (Skymet), said on 4 December:
"Rainfall in December is unusual for the Konkan belt. Not only Maharashtra, even Gujarat received a very heavy amount of rainfall. When we say unseasonal, we mean that these events are rare. It's not very common. This time it was rarest of all because Mumbai received nearly 100 mm of rainfall, which is a record for highest rainfall received by the city in 24 hours in December. Situation is, however, expected to get better tomorrow onward."
What Has Caused 'Record-Breaking' Unseasonal Rains?
The December rains can be attributed to a low-pressure area in the Arabian Sea and a western disturbance, as per the Indian Meteorological Department.
"There was a weather system in the Arabian Sea which came in the proximity of the coast which changed the wind pattern and caused clouding. It interacted with a weather system which moves up north and the combined effect caused this rainfall. This is definitely unexpected and untimely, and the frequency of such freak events is only increasing due to climate change."AVM (Rtrd) GP Sharma, President of Meteorology (Skymet)
Kashyapi further elaborated on the environmental factors that facilitated the formation of conducive conditions for rain -- a cause for worry.
"Upper air cyclonic circulation over the Arabian Sea resulted in heavy and untimely rains in Maharashtra. Initially, it was off the Karnataka coast and slowly moved northward. On 1 December, the location of this cyclonic circulation was off Maharashtra coast and a trough like low-pressure area extended throughout the Konkan region. These two combined, brought a lot of moisture. Districts such as Palghar, Thane, Mumbai, Raigadh upto Ratnagiri and Sindudurgh received heavy isolated rains," explained Kashyapi.
For Pune, the previous record was 53 mm of rain in December. This year, hwowever, several areas in Pune received as high as 103 mm of rain.
"While it used to rain in December previously, the frequency has only increased over the years," said Kashyapi.