Above: A bus is seen off the road near uprooted trees that have fallen on a main road in Alibag town of Raigad district, India, following the landfall of Cyclone Nisarga just south of Mumbai on Wednesday, June 3, 2020. (STR/AFP via Getty Images)
Cyclone Nisarga made landfall Wednesday on a portion of the west coast of India rarely affected by tropical cyclones: near the megacity of Mumbai (metro area population, 20 million). According to the India Meteorological Department (IMD), Nisarga (the Hindi word for nature) made landfall near 8Z Wednesday (1:30 pm IST) about 50 miles south of Mumbai as a high-end tropical storm with sustained 3-minute average winds of 62 – 68 mph. The Joint Typhoon Warning Center (JTWC) rated Nisarga a category 1 hurricane with 1-minute average sustained winds of 85 mph. Alibag, India (see photo above) reported sustained 10-minute average winds of 63 mph at 9Z Wednesday in the north eyewall of Nisarga, with a pressure of 985.5 mb. This was the weaker side of the storm, supporting the idea that Nisarga was at least a category 1 storm with sustained 1-minute average winds of 75 mph.
IMD estimated that the cyclone brought a storm surge of 1–2 meters (3.3–6.6 feet) to the Raigad Mumbai and Thane districts, to the south of Mumbai. The city of Mumbai was on the north side of where the center made landfall; the counter-clockwise circulation of the cyclone brought the city offshore winds and a much lower storm surge.
In addition to storm surge damage, heavy wind damage is likely to have occurred to the south of Mumbai, judging by videos posted to social media (like this one). There are preliminary damage reports of many fallen trees across Mumbai, but the brunt of the storm thankfully passed south of the city. Flood damage from heavy rains may be significant, though India is used to torrential rains from the annual monsoon. However, preparations for the heavy monsoon rains may have been less advanced than usual this year due to the Covid-19 pandemic. For example, according to this post, the city government neglected to clean out the storm water drains, resulting in destructive street flooding.
Mumbai rarely hit by tropical cyclones
Mumbai lies on the central west coast of India on the Arabian Sea at a latitude where the prevailing winds typically do not blow with a component from west to east, thus preventing very many tropical cyclone landfalls. This wind regime, in combination with the fact that the Arabian Sea typically sees only one or two tropical cyclones per year, means that Mumbai has rarely been affected by these great storms. According to NOAA’s historical hurricane database, only two other tropical cyclones of at least tropical storm strength have affected the Mumbai region in the past century: an October 16, 1940 system that made landfall in Mumbai as a category 1 storm with 75 mph winds, and a September 23, 1948 storm that passed just offshore from the city as a category 1 storm with 75 mph winds.
Nisarga formed in the “onset vortex” of the advancing southwest (summer) monsoon and will help pull the monsoon into India in the coming days. IMD is forecasting a near-normal monsoon in 2020, with precipitation of 102% of normal.
COVID-19 spread a concern in Cyclone Amphan’s wake
The 2020 North Indian Ocean cyclone season got off to a devastating start in mid-May, when Tropical Cyclone Amphan zoomed to category 5 strength with 160 mph winds and a central pressure of 907 mb, becoming the Bay of Bengal’s sixth category 5 cyclone in recorded history. Amphan made landfall near Kolkata, India, on May 20 as a weakening category 2 storm with 100 mph winds, killing 128 people. Amphan brought a devasting storm surge of up to 5 meters to the coast near the India/Bangladesh border, where widespread damage was reported to the Sundurbans mangrove forest preserve. Severe wind damage occurred in Kolkata.
Preliminary damage estimates are $13.2 billion in India and $129 million in Bangladesh. According to statistics at EM-DAT, this would make Amphan the costliest cyclone ever recorded in the Indian Ocean—and the third-costliest non-Atlantic tropical cyclone in world history.
In the wake of Amphan’s devastating landfall, cases of COVID-19 have shown a noticeable uptick in the Indian state of West Bengal, where Kolkata lies. This increase in disease spread may be due to 2 million people who were evacuated there in advance of the storm. A substantial rise in COVID-19 cases in the wake of Amphan was also observed in Bangladesh, where 2.2 million people were evacuated. Similar concerns are being raised for Mumbai, where at least 100,000 people were evacuated in advance of the landfall of Cyclone Nisarga.
Bob Henson will be back later today with an update on Tropical Storm Cristobal, which is drifting near the coast of southern Mexico but expected to move toward the U.S. Gulf Coast this weekend.
