Turbulent skies in Delhi and Mumbai: Unpacking the weather patterns behind recent storms

Recent weather events in Delhi and Mumbai are reminders of the dynamic and changing nature of urban environments under the influence of global climate patterns

Mumbai was hit by a thunderstorm that led to extensive infrastructure damage on the evening of May 13.

On Monday afternoon, dust storm and heavy rainfall lashed several parts of Mumbai and the adjacent areas. (Unsplash)

The storm brought a short burst of intense rain to the suburbs but also spurred a large volume of loose dust into the air, worsening air quality significantly.

The squall triggered the collapse of a 100-foot-tall giant hoarding in Mumbai’s Ghatkopar resulting in 14 deaths and 74 injuries (until May 14 afternoon), among other incidents of infrastructure damage and waterlogging.

According to the Regional Meteorological Centre (RMC), Mumbai, India Meteorological Department (IMD), winds reached a peak speed of 40 knots (approximately 74 km/h) at 3.30 pm, highlighting the storm's ferocity and its ability to disperse dust particles throughout Mumbai.

Additionally, the weather station at Santacruz airport recorded winds ranging from 55 km/h to 75 km/h around 4.30 pm on May 13; visibility at the airport decreased significantly from 4000 metres at 3.30 pm to only 500 metres by 4 pm.

Meanwhile, Delhi was hit by a dust storm, triggered by a strong anticyclonic trough that swept across parts of Northwest India on Friday, May 10. The trough led to strong winds with gusts up to 60 km per hour, stirring up large amounts of dust and significantly reducing visibility in the region. This weather pattern was influenced by intense heat in northwest India and parched soil conditions due to a lack of rainfall. Visibility was notably reduced, dropping to as low as 1,000 metres in some areas of the city, the IMD said.

Weather bureau says common occurrence for Mumbai in May, but other experts differ

Sunil Kamble, director at RMC Mumbai, IMD, shared details on the recent weather events. "The recent storm in Mumbai might be perceived as a dust storm, but it was predominantly a thunderstorm. Such pre-monsoon thunderstorms are not uncommon in May. Typically, they are localised phenomena with wind speeds ranging from 40-50 km/h, and occasionally gusting to 60-70 km/h. Although gusts reaching up to 75 km/h are less frequent, they are not unheard of.”

These thunderstorms usually last around 1.5 hours, and in this instance, the Santacruz weather station recorded 21 mm of rain in just two hours, he said. “The phenomenon involved a downdraft, where cold air rapidly descends, hitting the ground and dispersing surface particles—often exacerbated by urban construction—followed by an updraft, which lifts these particles back into the air, creating the appearance of a dust storm. This sequence of events is something we have observed before during May in Mumbai,” said Kamble.

Although milder, Mumbai is expected to witness similar afternoon thunderstorms in the coming week, said Kamble. “While the excess wind speed during Monday’s event was not anticipated, we will be issuing nowcast hourly bulletins and impact-based forecasts to alert the corporation and citizens,” he said.

Private weather forecaster Skymet’s vice president (meteorology and climate change) Mahesh Palawat said: “The severity of Mumbai’s weather event was definitely not anticipated. A weather system — trough (an elongated region of relatively low atmospheric pressure, often associated with fronts and areas of increased rain) — extending from Vidarbha to south Tamil Nadu further aided the localised thunderstorm to strengthen over the Mumbai coast.”

Meanwhile, Sachin Ghude, scientist from the Indian Institute of Tropical Meteorology (IITM), Pune, agreed that it was not a dust storm. “Dust storms originating in the Middle East (West Asia) can significantly impact distant cities like Mumbai, as powerful winds carry dense clouds of dust thousands of kilometres, deteriorating air quality and reducing visibility upon arrival. Our weather models did not show any sign of transport of dust from the Middle East. Monday’s thunderstorm was not such a weather event as it was a more localised thunderstorm that managed to erode a lot of dust from the high amount of construction activity in the city.”

Ghude however highlighted that it was a ‘peculiar’ and ‘rare’ phenomenon for Mumbai. “The wind speed was very high even for a localised weather event such as this. Local surface heating has resulted in thunderstorms for 2-3 hours during the evenings across cities such as Mumbai but the sudden uptake of winds touching 74 km/h that resulted in infrastructure damage is a rare and peculiar phenomenon for Mumbai,” he said.

The difference between a dust storm and thunder storm

Dust storms are similar to thunderstorms (convective systems) with a spatial dimension of a maximum of 8-10 km, said Madhavan Nair Rajeevan, former secretary, the Earth Sciences ministry adding that sometimes many such clusters move together (called squall line) that may extend a few hundred kms.

“The difference between a dust storm and a thunderstorm is the cloud base of a dust storm is much higher (maybe almost 2 km from the surface) but thunderstorm clouds have a low base. Therefore, in a dust storm, rain does not reach the ground. Only the strong winds associated with the downdraft reach the ground and raise dust (in Rajasthan it will be a sand storm) on its way. The major impact of a dust storm is therefore associated with strong winds. It could reach even 100-120 km per hour,” said Dr Rajeevan.

Thunderstorms and dust storms are natural weather systems and are triggered by certain synoptic conditions, he added.

Dust storms in the pre-monsoon period are not unusual, explained Akshay Deoras, a researcher at the National Centre for Atmospheric Science, University of Reading, UK. “Summer daytime heating along with an instability in the atmosphere and other factors can trigger thunderstorms, which can then trigger dust storms since the land surface is typically dry in this period. North India has seen even more deadly dust storms in the past, including dust storms in May 2018 that reportedly killed over 100 people. In Mumbai’s case, the blanket of dust during the storm on May 13 was quite unusual. However, it was not surprising since the thunderstorm travelled from the dry land surface in the eastern outskirts,” said Deoras.

Climate change connection

The frequency and intensity of these dust storms are closely linked to broader impacts of climate change. Experts argue that human-inflicted global warming, along with local environmental degradation such as deforestation and urban sprawl, contribute to these phenomena.

“Global warming affects these mesoscale systems like dust storms. Since higher temps help the atmosphere to hold more water vapour, in a warming world, thunderstorms and dust storms will be very severe,” said Rajeevan adding, “Urbanisation also plays a role in terms of high heat content (that means energy) and heterogeneous terrain. Urban cities can hold up moisture and heat and thus energy. In future warming climates, we should expect more severe thunderstorms and dust storms.”

Moreover, meteorologists have noted that such storms are part of a larger pattern of extreme weather events. This includes higher temperatures and prolonged dry spells that create ideal conditions for thunderstorms. The lack of moisture in the air and intense heat help lift more dust, and strong winds carry it over large distances, impacting cities such as Delhi and Mumbai​​.

Implications for urban centres

Experts suggest that addressing the root causes of these weather events, particularly environmental factors and climate change impacts, is essential for mitigation. “This includes policies focused on sustainable land use, reforestation, and strict regulations on industrial emissions to reduce the underlying vulnerability of these urban areas to dust storms,” said Rajeevan.

“In the case of Mumbai, models unfortunately cannot exactly tell when the storm will come. They can suggest whether there is a chance. We need to monitor the development using doppler radars. The Earth Sciences Ministry should install the four X band radars at the earliest which have been planned for the city for higher accuracy.”

The recent weather events in Delhi and Mumbai are reminders of the dynamic and changing nature of urban environments under the influence of global climate patterns. As these incidents become more frequent and intense, they underscore the urgent need for integrated climate resilience strategies in urban planning and policy-making to safeguard public health and ensure the sustainability of city environments.