Unusual La Nina will bring lower temperatures in December

Photo courtesy of Larry Gordon.

A snowier winter that starts colder than average but warms up above normal in January and February could be on the way, thanks to a cold weather phenomenon in the Pacific Ocean.

La Nina is not uncommon in itself. What is unusual is experiencing it multiple seasons in a row. La Nina has influenced winter weather patterns over the past three years, a phenomenon that was last experienced in 1998 to 2001.

National Temperature Map (CNW Group/Pelmorex Corp.)

National Temperature Map (CNW Group/Pelmorex Corp.)

“We’re talking about water temperatures in the equatorial Pacific. Our record is not extremely long,” said Weather Network Meteorologist Michael Carter. “We can’t go too far back in history because we just didn’t have observations prior to the last 50, 60, 70 years, but we have not seen this pattern recur this frequently more than a couple of times.”

The colder water in the Pacific Ocean influences the Global Jet Stream, pushing it further north and south.

“What that does is open the door for more Arctic influence,” explained Carter. “This year, our indications are that it is going to open the door for the Polar Vortex to play a big role, especially in the early part of the winter.”

That will mean a chillier December, which typically means within a degree or two of the freezing mark in southwestern Ontario. It also creates more unsettled weather, more storms, and with lower temperatures, more snow.

Carter is putting his money on a white Christmas, even in Windsor in the extreme southwest, where the chance of snow on Christmas Day is about 50-50.

The Weather Network will have a more detailed Christmas Day forecast closer to the date.

After December, weather patterns could change considerably. Carter expects warmer air in the region and, with it, temperatures averaging above normal.

“Those warmer air masses from the south will have more opportunity to fight back a bit,” Carter said. “Milder, maybe even extended thaws. Maybe even a false start to spring this year.”

Once the temperatures warm, he predicts rain, more than snow, as unsettled patterns continue.