Winter has officially arrived in the city.
Residents had been feeling a nip in the air for around a month but the parameter that matters the most has been fulfilled only recently. If the minimum temperature remains less than 13°C for more than a week in Patna, winter is considered to have arrived. (See chart)
Weathermen although claim the temperature is slightly higher than the expected level at this time of the year because of the formation of very severe cyclonic storm, Madi, over the Bay of Bengal.
Heavy moisture incursion from Madi formed low-level clouds over Patna on Tuesday and obstructed the Sun’s rays to reach the Earth’s surface. The hazy skies, as seen till around 12 noon, are expected to be observed till Thursday.
The presence of high level of moisture in the troposphere, the lowest level of the atmosphere, at this time of the year keeps the solar heat from reaching the earth’s surface during the daytime and obstructs drastic drop in the night and early morning temperatures.
“The effect of Madi is expected to last till December 13 and northerly and northeasterly winds would blow at an average speed of 3-5kmph. At present, the moisture level is around 65 per cent, around 20 per cent higher than what is normal at this time,” said Ashish Sen, director, India Meteorological Department, Patna.
The onset of winter in most parts of eastern India has been affected by frequent formation of cyclonic storms in the Bay of Bengal over the past few weeks. First, cyclonic storm Helen formed in Bay of Bengal around November 20 followed by Lehar around November 28 and now Madi.
Sen added: “These weather systems cause a heavy level of moisture incursion in the troposphere, restricting the drop in the mercury column. Madi would be the last cyclone in the Bay of Bengal this season. The temperature is expected to start dropping from December 13. The minimum temperature would be 8 to 9 degrees Celsius by December 20.”
Apart from the drop in temperatures from Friday, the residents can also expect foggy conditions from this weekend.
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