Winter has come a fortnight early but experts are not sure how long it will stay, given the year’s bizarre weather patterns. “For all you know, it might leave earlier than usual,” said O.P. Sharma, the chief meteorologist in a private agency.
Metro decodes the freak meteorological year that is.
Summer heat waves
A heat wave scorched the city from April 18 to 28. The period was the hottest in six decades with the mercury crossing 40 degrees eight times.
May began with a nine-day heat wave when the mercury soared to 41.8 degrees.
Local factors: Nor’westers could not develop as there was not enough moisture in the lower troposphere.
Global factors: Hot, dry northwesterlies and westerlies blew in from central Asia because of the heat wave in central and north India.
Monsoon’s early arrival
Rains arrived on May 25, a fortnight before schedule, powered by Cyclone Aila.
Local factors: The formation of the cyclone over the Bay.
Global factors: Experts blame Aila’s ferocity — responsible for the monsoon’s early arrival — on global warming.
June heat wave
After entering Bengal on May 25, the monsoon flow took 30 days to get activated. So, June was dry and hot. A weeklong heat wave tormented the city from June 7.
Local factors: Lack of enough moisture in the lower troposphere, hindering formation of rain clouds.
Global factors: El Nino (warming of sea water) over the Pacific Ocean delayed monsoon activation.
Maverick monsoon
Rainfall from May to August was 10 per cent below average. But the city finally closed its monsoon account with 15 per cent surplus rainfall, thanks to a surge in showers in September. The city received over 300mm rain between September 3 and 9 and more than 360mm in the Puja month (22 per cent more than usual).
Local factors: Variation in moisture content.
Global factors: El Nino, global warming and MaddenJulian Oscillation or MJo (fluctuation in atmospheric pressure over oceans).
November swelter
The first half was the hottest in five decades. Minimum temperature on November 15 was eight degrees above normal.
Local factors: A high-pressure belt over the Bay.
Global factors: None.
Winter comes early
The mercury started dropping after the November 16 rain; winter set in on Sunday.
Local factors: A low-pressure area over south Bengal.
Global factors: Wet wind from the Mediterranean Sea and the northwesterlies
