Saturday felt like the coldest day of this winter for many Calcuttans, despite the minimum temperature staying above normal.
Met officials linked the feeling to the day temperature, which was way below normal, and a steady breeze. A persistent blanket of fog kept the sun hidden or timid for hours, causing a sharp slide in the maximum temperature. Prime Minister Narendra Modi’s helicopter could not land in Nadia’s Taherpur due to low visibility. The chopper returned to Calcutta, from where Modi addressed the rally virtually.
At 20.7 degrees Celsius, the maximum temperature in Alipore was five degrees lower than the normal temperature in late December. At 16.2, the minimum was a notch above average. Most of the day was damp and gloomy. The winds that made the day feel colder were northerlies that came from Bihar and north Bengal, said a Met official.
Sunday is likely to be brighter and warmer, according to the forecast.
“Cold and dry northwesterly winds from Kashmir have more effect on the night temperature. It slides when the winds are dominant. Very strong northwesterlies also cause a dip in the day temperature. But from Friday night, northerly winds have been dominant near the surface. The upper levels of the atmosphere were dominated by moisture-laden easterly winds from Bangladesh and the Bay. The moisture contributed to the formation of fog,” said H.R. Biswas, head of the Regional Meteorological Centre in Alipore.
“The difference between the minimum and maximum was barely four degrees, instead of the usual gap of over 10 degrees. The moisture content was on the higher side throughout the day,” he said. The minimum relative humidity for the day was 68 per cent.
Shallow to moderate fog was reported from across the state on Saturday, the Met office said. A combination of moisture, clouds and light wind contributed to the formation of the fog. The moisture prevented a slide in the minimum temperature.
Some shallow fog or mist is likely on Sunday morning as well. But it will not linger as long as it did on Saturday, said a Met official. As the sky clears and the sun shines, the maximum temperature is expected to rise to around 24 degrees. The effect of the low day temperature on Saturday was visible across the city. A warm layer of clothing was needed even at noon.
The minimum temperature, a marker of how cold the night was, is recorded before sunrise, when the city sleeps. The effect of the maximum temperature lasts much longer. Any sharp slide in the maximum, especially in winter, makes the entire day feel colder than usual.