The Colaba observatory recorded 791 mm of rainfall during the first week of July, surpassing the average rainfall received by the city for the entire month. The Santacruz observatory recorded 879 mm of rain, just below its monthly July average of 919.9 mm.
The intense rainfall has raised questions about the changing behaviour of the Indian monsoon, particularly in the context of El Nino and climate change.
El Nino is a naturally occurring climate pattern in which the waters of the Pacific Ocean become warmer than normal. It has traditionally been associated with weaker monsoon conditions and below-normal rainfall in India.
This year, the monsoon initially followed that pattern, arriving in Mumbai nearly two weeks later than usual. However, after its delayed arrival, the rainfall intensified dramatically, producing extreme rain events instead of a gradual and consistent monsoon spell.
Scientists explain that there is no contradiction between El Nino conditions and intense rainfall events. While El Nino can influence the timing and strength of the monsoon, climate change is increasingly altering rainfall patterns. Instead of continuous rainfall spread over several weeks, cities are witnessing fewer rainy days accompanied by extremely intense downpours.
A warmer atmosphere is capable of holding greater amounts of moisture. As global temperatures rise, both the atmosphere and oceans retain more water vapour. When favourable weather conditions develop, this accumulated moisture is released rapidly, causing intense rainfall over short periods rather than prolonged moderate showers.
Mumbai’s rainfall trends reflect this changing pattern. Between 1981 and 2000, the city recorded an average annual rainfall of around 2,325 mm. Over the past two decades, the average has increased by nearly 15 per cent, reaching approximately 2,673 mm.
Meteorologists stated that this week’s extreme rainfall was the result of multiple weather factors working together rather than a single weather system. Moisture levels from the Arabian Sea increased due to changing wind patterns associated with warming over the Middle East. At the same time, a low-pressure system over the Bay of Bengal supplied additional moisture to the atmosphere.
As these moisture-filled winds reached the Western Ghats, they were forced to rise, triggering exceptionally heavy rainfall over Mumbai and surrounding regions.
After several days of continuous rainfall, the city has finally received some relief. For the first time in five days, daily rainfall remained below the 100 mm mark, with Santacruz recording 94 mm and Colaba receiving 90 mm.
Although a yellow alert continues to remain in place, the weather forecast for the coming days indicates a significant reduction in rainfall intensity. Only light showers are expected across Mumbai and neighbouring Thane, providing the city with much-needed time to recover from the impact of the extreme weather event.
The recent rainfall episode highlights the growing unpredictability of monsoon patterns, where delayed arrivals can be followed by sudden and severe downpours. Mumbai’s experience underscores the increasing impact of climate change on urban rainfall behaviour and the challenges posed by extreme weather events.
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