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Shower hope for Monday

Calcuttans deceived by an overcast sky on Sunday morning can hope for rain in the next 24 hours.

Met experts said light thunderstorms and rain are likely in some places of Gangetic Bengal in the next 24 hours as the situation is favourable for the formation of rain-bearing clouds.

A Nor’wester, however, is unlikely as conditions are not ideal for such storms over the Chhotanagpur Plateau, an expert said.

The clouds that kept appearing in the sky throughout Sunday took the sting out of the sun’s rays and dragged the maximum temperature below normal for the first time in over a week.

On Sunday, the maximum temperature was 35.1 degrees Celsius, a notch below normal during this time of the year.

“At 8am today, the sky was so overcast that I felt sure it would rain. But suddenly the clouds thinned and by 10am, the sun was beating down as usual,” said Aditi Ghosh, 23, a resident of New Alipore.

Scientists at the India Meteorological Department, Calcutta, said the wind blowing from south in the morning led to the cloud build-up but it lacked the strength to trigger showers.

“The wind from the Bay of Bengal was blowing at a speed of only about 4kmph. So, it did not contain enough moisture to bring rain,” said a senior Met official.

“To trigger a brief spell of shower, the wind should have blown at a speed of at least 10kmph.” The southerly winds sustained throughout the day and is set to blow on Monday as well.

slowly accumulated more moisture. It is likely to continue till Monday and hence, there is a possibility of rain,” said an official.

Over the last week, the city has been going through a very hot phase with the maximum temperature ranging between 36.5 and 37.5 degrees Celsius.

What was going against the formation of thunderclouds was that there wasn’t enough moisture in the air. So, people were feeling a dry heat uncharacteristic of Calcutta summers.

The minimum relative humidity, which reflects the water vapour in the air during the hottest period of the day, had come down to 13 per cent last Thursday, the lowest it has been in over a year.

Since then, however, minimum RH has trebled in three days.

“You need both heating and moisture in the air for thunderstorms to develop. On Monday, we are likely to have both,” said a senior Met official.

The rise in humidity level in the air has also increased the discomfort of people during the day.

At 2.30pm on Sunday, the maximum temperature read a relatively low 35 degrees Celsius. But the relative humidity was a high 50 per cent. Thus the discomfort index or the effect of these two factors on the human body, read 61.6 degrees Celsius, six degrees above the comfort level, a met official pointed out.

He said there was, however, not much chance of a Nor’wester on Monday as the conditions were ideal for one to be generated over the Chhotanagpur Plateau.