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Vinson Kurian

RARE PHENOMENON: This picture of the waterspout that formed under a cumulonimbus cloud formation off the Kovalam coast on Sunday evening was captured in digital camera by a tourist, Samriti Goyal, who was on the beach when it occurred.

Thiruvananthapuram , Oct. 20

THE Met Office here has confirmed that the "fearsome spectacle" of a column of seawater rising into the evening sky, reportedly with a glowing crown buffeted in smoke, and spotted 2 km off the Kovalam beach near here on Sunday evening, was indeed that of a tornadic `waterspout'.

The second such occurrence along the Kovalam coast in the last 10 years, the spout was found tagged to the base of a large cumulonimbus cloud that had descended downwards to the sea surface, Mr M.D. Ramachandran, Director, Met Office, Thiruvananthapuram, quoted witnesses as saying. A resident Grade II meteorologist, who happened to be around, witnessed the rare phenomenon as it unfolded itself before a petrified holiday crowd.

Waterspouts are rotating columns of air similar in appearance to that of the tornado in which a large mass of water rises into a column by the sheer force of prevailing winds. At Kovalam on Sunday, the base of the water column measured up to1 km, rose 10 to 15 ft in height and held itself to that position for "quite some time," before draining out.

When a slow moving tornado begins to form over water, it can spin down from the clouds and develop a funnel of water and spray. The spray is generally fresh water, formed through condensation and the rest of the water is whatever has been sucked up.

It is believed that the spray, lit from the back by the setting sun, may have contributed to the "smoke and flaming crown" effect. Spouts are known to develop over warm ocean currents during unstable conditions or as "cold front" boundaries pass over the ocean.

(A cold front occurs when a cold air mass moves into an area occupied by a warmer air mass. Moving at an average speed of about 20 mph, the heavier cold air moves in a wedge shape along the ground. Cold fronts bring lower temperatures and can create narrow bands of violent thunderstorms).

Spouts can harm passing boats and yachts. Because they are over the ocean, they do not pick up debris but water spray is observed at the base.

Spouts can develop over the ocean and move over the land. It is then they are then called tornadoes, which can be dangerous and has caused extensive damage to trees and buildings as well as overturned caravans in coastal communities.

Once on the land, they dissipate fairly quickly. On the ocean however, they can last much longer.

`Spouts' are common occurrence

Waterspouts are a fairly common meteorological phenomenon, and are often referred to as tornadoes over the sea. Though rare in the Kerala seas, they are known to occur frequently in the Bay of Bengal, off the West Bengal coast.

There are, in fact, two types of waterspouts, tornadic and fair weather. The former, generally the more dangerous of the two, actually forms as a tornado over the land and drifts out to sea. Fair weather waterspouts, which are by far the most common of the two varieties, are most likely to form over the open sea, or large lakes, in the late summer or autumn when the sea temperature is at its highest.

When a cool mass of air moves over the warm sea, the air becomes very humid and unstable, and this sets up strong convection currents, which may be sufficient for a waterspout to develop. These spouts only last for a short time, perhaps only as long as 20 minutes, and move slowly up to a speed of 20 miles or less per hour before the decaying stage arrives.

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Tornadic `waterspout' seen at Kovalam

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