April fools rain factors thrice

Rith Basu, TT, April 16: Calcutta's arid April today dodged three potentially strong rain elements to keep its slate dry.

From a thundercloud formation caused by a cyclone over the Bay of Bengal to low-pressure zones in Bihar and Odisha, nothing could bring a drop of rain to the parched city. The Alipore Met office said the chance of these three weather systems having any impact would diminish further on Monday.

Brace for hot and humid weather over the next couple of days unless a thunderstorm in the neighbourhood brings relief by blowing into the city.

In a normal year, Calcutta gets up to four such thunderstorms in April, usually after a hot and humid afternoon. The cyclone that could have altered the rain equation - named Maarutha by Sri Lanka - and the twin low-pressure systems in the neighbouring states had created conditions perfect for an evening storm and shower. The missing factor was direction.

"Humidity is a prerequisite for the formation of thunderstorms and there was ample moisture in the air in south Bengal on Sunday due to the presence of the cyclone, the cyclonic circulation and the trough in the vicinity," said Sanjib Bandyopadhyay, deputy director-general of the India Meteorological Department (IMD), Calcutta.

Thunderclouds had developed to the west of the city, just as the weather office had expected, but they skirted the city while moving in from the north-westerly direction. "This is why there was no rainfall here," Bandyopadhyay said.

Clouds have formed in south Bengal on several occasions this month, but every time they have either skimmed Calcutta or fizzled out just before reaching the city.

According to meteorologists, several factors, including wind direction at higher levels of the atmosphere and moisture content of the air, decide how long clouds would be potent and in which direction they would move.

The pieces of this weather grid have not quite fallen into place for the city this summer.

Maarutha is unlikely to change the pattern, the weather office said.

"Cyclone Maarutha is headed towards Myanmar, away from Calcutta. It is expected to make landfall near Sandoway in Myanmar around Sunday midnight and degenerate rapidly into a depression," weather scientist Bandyopadhyay said.

Fishermen along the Bengal and Odisha coasts have been warned of rough seas.