Malabar Hill resident Darshan Khatau was pleasantly surprised to spot a rare weather phenomenon on Monday morning. He saw a waterspout or water-tornado — a rotating vertical column or funnel shaped cloud formation as an intense vortex over water —around 3 km off the coast of Mumbai from Malabar Hill, near Prongs Lighthouse at 9.15am.
“I saw it when I had stepped out on my balcony to take photographs of birds like I do daily. The phenomenon lasted for about 20 seconds and I managed to take two short videos. The location of the waterspout may not have been more than 1 km off Colaba early this morning. Owing to cloud cover and haze, the photos were not very clear,” said Khatau, an avian and wildlife enthusiast who has documented several bird species.
A similar image of the waterspout was shared on social media by Seju Nair on Twitter. The posts stated that it was spotted near Marine Drive on Monday morning.
Some isolated spells of light rain were recorded in different parts of the city and suburbs on Monday.
HT shared Khatau’s videos with the weather bureau, Union earth sciences ministry and independent meteorologists.
Mrutyunjay Mohapatra, director general, India Meteorological Department (IMD), called it a ‘rare occurrence especially close to the coast’. “This does not happen frequently. Whenever there is any convective activity (vertical transport of heat and moisture in the atmosphere from warmer surface area and lifted to cooler zone) followed by thunderstorms, this kind of weather phenomenon is witnessed,” he said adding, “This phenomenon is a tornado when it occurs over land, and over sea it is termed as a waterspout. It can happen over a river, large pond, and over the ocean. During the monsoon season, whenever there are convective clouds, it can occur in coastal areas.”
M Rajeevan, secretary, ministry of earth sciences said, “This is an atmospheric phenomenon. It is a rotation of the cloud that comes down and pulls up water. Owing to convective currents, there is a down-drop effect which pulls up the water in a rotational manner for a small time frame.”
Mohapatra said the phenomenon was also reported off Vishakhapatnam coast earlier this monsoon. Even during the landfall of severe cyclone Nisarga during the first week of June this year, it was observed by the fishing community off Shrivardhan coast in Sindhudurg.
“The coverage area is less than one kilometre where there is intense downpour of water within that column. In some cases, it lifts water from the water bodies and falls less than 500 metre away dropping fish or other aquatic life at a distance from the emergence of the system,” said Mohapatra.
Unfortunately, it is very difficult to detect through radars and only eye witness records have been relied on, said Rajeevan. “We do not have a good record or statistics of such events. Only this kind of qualitative record is there. However, we have to check our radar data for convective clouds for that period on Monday morning. The whole thunderstorm activity is short-lived (one or two hours) and convective clouds die off quickly. Thus, such a phenomenon is also short-lived,” he said.
IMD’s Mumbai regional meteorological department in Colaba confirmed the presence of convective clouds over south Mumbai and off the coast on Monday from 9am onwards.
Independent meteorologists said these events generally happen at least 20 miles off the coast and are common in deep oceans. However, it is rare to have happened closer to the coast, said professor Sridhar Balasubramanian of department of mechanical engineering and IDP Climate Studies, Indian Institute of Technology-Bombay. “There is an active circulation in the Arabian Sea off Mumbai coast. Mumbai has also been witnessing thunderstorms since October 3. The active circulation could have led to the formation of this super cell thundercloud where intense convective activity in that area led to this abrupt vertical abrupt phenomenon and formation of a large cumulonimbus (dense tall vertical) cloud followed by this funnel shaped formation. If it happens over land (tornado), it is rare. In the ocean, it is possible due to the presence of strong vertical currents,” he said.
Akshay Deoras, independent meteorologist and PhD researcher at the University of Reading, United Kingdom, said, “From the photograph and observed meteorological conditions, it appears that this was a fair weather waterspout. Satellite images show the presence of developing cumulus clouds off south Mumbai coast at the time of the event. Fair weather waterspouts form along such cloud bases.”
What are waterspouts or water-tornadoes
Waterspouts are generally classified into two categories: tornadic and fair weather. Fair weather waterspouts are more frequent and less destructive than tornadic waterspouts and they usually form during morning hours. An interaction of warm air near the water surface with cooler air creates atmospheric instability, which forces the moist air to rise and then condense. If there is sufficient wind shear (change in wind velocity with height), the air column starts spinning and a waterspout forms.
(Source: Akshay Deoras, independent meteorologist and PhD researcher at the University of Reading, United Kingdom)