Kolkata residents bundled up against a severe chill on Saturday morning as the city's mercury plunged to a season's low of 12.8 degrees Celsius, marking the coldest day witnessed so far this winter. This reading dipped just below Friday's minimum of 12.9°C, intensifying the winter bite across the metropolis.
Persistent Chill and the Upcoming Shift
According to the Regional Meteorological Centre (RMC), the prevailing cold conditions are driven by a strong northwesterly wind and shallow fog, which together block the already weak winter sunrays. This combination is expected to keep temperatures around 13°C until December 30.
However, a change is on the horizon. Weather officials forecast a marginal rise in the minimum temperature to around 14°C on December 31 (New Year's Eve), offering some respite to revellers. "The temperature will continue to hover around 13°C until Dec 30. We have a strong northwesterly along with fog at the lower levels... These two have combined to pull the temperature down," explained HR Biswas, deputy director-general of meteorology.
Western Disturbance to Influence New Year Weather
The slight warming trend is attributed to an approaching Western Disturbance (WD) – an extra-tropical storm originating from the Mediterranean region. This system is set to affect north Bengal significantly and will move towards the east and northeast.
"Then, we have a WD forming in northwest India that will sail towards the east and northeast. It will result in a slight temperature rise from Dec 31 to Jan 1," Biswas added. While Kolkata and south Bengal may not receive rainfall, an increase in cloud cover due to the WD is predicted to push temperatures further up to the 14°C-15°C range on New Year's Day. The WD typically blocks the chill-carrying northwesterly winds, leading to a rise in mercury levels.
Regional Temperature Variations and Historical Context
The cold wave has gripped the entire region. On Saturday, Sriniketan in south Bengal recorded the lowest temperature at 9.7°C. In the northern parts, Alipurduar's plains saw a low of 8°C, while the Darjeeling hills shivered at 4.5°C.
In Kolkata, while the minimum was a degree below normal, the maximum temperature on Saturday was 22.9°C, which is 2.5 degrees below the usual mark. This month has seen maximum temperatures remaining below normal on 24 out of 27 days. For perspective, the coldest December day in recent memory was on December 29, 2018, when the city recorded 10.6°C. This season, the lowest minimum so far was 12.5°C on December 15.
The RMC has forecast that shallow to moderate fog will persist over south Bengal and Kolkata for the next two to three days. Meanwhile, the maximum temperature in Kolkata is expected to climb, potentially touching 24°C around December 31 to January 1.
