CHENNAI: City residents have been waking up to hazy weather and poor visibility, but hours before the mist arrives, night temperatures have been dropping below normal.
Weathermen said below normal night temperatures are likely to continue due to the incoming cold and dry northerly winds at least for the next two days. Bloggers said day temperatures may be a degree or two above normal this month, but would begin rising in March before the official onset of summer.
For the next 48 hours, the city and its suburbs are likely to experience haze/mist early in the morning as the skies may be partly cloudy. The maximum temperatures may be at 31 degrees C-32 degrees C and the minimum at 20 degrees C-21 degrees C.
"Misty mornings are normal for this season. It forms when temperature drops below dew point and water vapour condenses. This is also due to a lack of strong easterly winds. Mist dissipates once the sun rises," an IMD official said.
On Tuesday, Nungambakkam and Meenambakkam weather stations recorded 20.3 deg C and 20.1 deg C just before sunrise, which were two degrees below normal in both the stations. The day temperatures touched 30.8 deg C in Nungambakkam and 32.3 deg C in Meenambakkam, which was one degree above normal.
Mahesh Palawat, chief meteorologist, Skymet Weather, said the unobstructed flow of cold and dry northerly winds will keep the night temperatures down at least for the next two days. "At present, temperatures have dropped in many parts of northwest, central and east India. The cold winds from there are moving up to Telangana and Tamil Nadu leading to drop in temperatures. This will continue for the next 48 hours. After that a western disturbance will block the flow of northerlies leading to temperature rise," he said.
Blogger Pradeep John said the rise in day temperatures and below normal night temperatures are due to a high pressure in the upper atmosphere. In regions of high pressure, air generally moves downward and warms, leading to drying and clear skies. Since there are no clouds, there is more incoming shortwave radiation and temperature rise during the day and escape of the heat during night leading to a dip in temperatures.
"This condition is likely to continue for the rest of February. By March, day temperature may rise further as the Sun crosses the equator to travel northwards," he said.
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