April 19: A wind-swept, overcast Wednesday that had held out hope for the first spell of rain in Calcutta this April brought no more than a drizzle in the evening, thanks to yet another killjoy in the weather clan.

Normally, a confluence of hot and humid winds leads to the formation of thunderclouds and rainfall. On this occasion, the speed of the south-westerly wind - it peaked at 40kmph - worked against the formation of rain-bearing clouds, the weather office said.

"At the moment, hot winds are blowing from north India towards the east. But the strong south-westerly wind pushed the north wind away on Wednesday, preventing the confluence that is crucial to the formation of thunderclouds," said Sanjib Bandyopadhyay, deputy director general, India Meteorological Department, Calcutta.

The consolation was a slight dip in the maximum temperature after two days of sweltering heat. The south-westerly wind blowing from the direction of the Bay of Bengal filled the atmosphere with moisture, providing relief from the pent-up heat that had made the minimum temperature shoot up three notches above normal to 28.1 degrees Celsius.

The maximum temperature, which is recorded during the day, was a degree below normal at 33.7. The discomfort index too was lower than in the past few days, although minimum relative humidity increased from 52 to 67 per cent. Wind was the saviour on what would otherwise have been another sweat-inducing day, Met officials said.

A north-south trough of low pressure stretching from Bihar to Odisha was another factor that prevented the confluence of south-westerly and north winds. Whenever there is a confluence of these winds, moist air from the direction of the sea gains altitude rapidly to form tall cumulonimbus clouds.

The evening drizzle was triggered by a thundercloud that had developed to the southwest and was floating past the city.

According to the forecast, conditions are still conducive to the development of thunderclouds in the south Bengal districts. "Generally, scattered showers are expected in south Bengal on Thursday, but only after clouds develop would we be able to say which places would receive rain," weather scientist Bandyopadhyay said.

Wind charts showed a high-pressure belt over the Arabian Sea, just off the Gujarat coast.

Pre-cyclone meeting: Representatives of various agencies like the state disaster management department, CESC, BSNL and the railways attended a routine meeting on cyclone preparedness at the Alipore Met office today. Such meetings are held every year ahead of the cyclone season in April-May.