Winter continued to blow hot and cold in Calcutta.
Tuesday’s minimum, at 15.3 degrees Celsius, signified the temperature fluctuations that the city has been experiencing since the onset of winter because of various atmospheric conditions that had cut the flow of the North Wind every now and then.
The second consecutive warm and humid day stood out against the 12.4 degrees, by far the season’s lowest, that Calcuttans enjoyed last Sunday.
The weather office said the temperature tumble would begin again on Thursday since the system that caused the mercury to shoot up has dissipated. This means, the chilly North Wind will have unhindered access to the city and the cold will be back.
The forecast says the minimum is likely to drop to 12 degrees Celsius by Thursday.
Fog, another harbinger of chilly conditions, enveloped the city for the good part of the day. Weather experts said a cyclonic circulation — that originated over Rajasthan and hurtled towards the east — drew a lot of moisture from the Bay of Bengal and these water droplets hung over the city as fog.
“The excess moisture in the city air was keeping the cold winds at bay. But the North Wind is slowly blowing away the moisture,” said G.K. Das, meteorologist at the Regional Met Office, Alipore.
The circulation had developed over Rajasthan as a residual effect of a western disturbance and began moving east early this week.
On Sunday, when there was no hindrance to the North Wind, the mercury had dipped to 12.4 degrees. But the circulation soon reached Calcutta and the coastal region, blocking the chilly air. Thus, the minimum temperature shot up on Tuesday by 2.5 degrees to reach 14.9 degrees Celsius on Monday.
A downward slide of the mercury was expected from Wednesday since the system had disintegrated.
The minimum relative humidity was 52 per cent on Monday, quite high by winter standards, but fell to 49 per cent on Tuesday since moisture incursion from the sea has stopped. A steeper slide is expected on Wednesday, allowing free flow of the northerly wind.
The weather office, however, refused to commit the number of days the chill would continue.
“At the moment there is no other weather system to block the North Wind. If the situation prevails, cold conditions could continue. The trend this season has been of too many western disturbances in north India, leading to rise in temperature in Calcutta. Sometimes these systems have taken the shape of cyclonic circulation. It is difficult to make a long-term forecast,” said a weather scientist at IMD, Calcutta.
“Bizarre… this winter has been bizarre. Every dip of the mercury is followed by a hot spell. I fear we may not have a reasonably long chilly phase at all,” grumbled Anchal Pradhan, 32, a homemaker from Alipore.
Meteorologists assured that there was still some time left this winter for biting chill to set in. Records from the past 10 years suggest that the chilliest day has been after January 9, they said.
The day temperature has, however, remained below normal for the past few days owing to a rise in the moisture content in the air.
Monday recorded 24.1 degrees Celsius while Tuesday’s high was 23.9 degrees, both two notches below normal. A similar forecast was made for Wednesday. “Expect sun and clear skies with strong winds blowing from the north, pushing the mercury down,” a Met official said.