Weakening westerly jet streams around the poles allowed cold arctic winds to sweep through Canada and parts of the U.S., eventually stalling on the Island, leading to a month long freeze that still promises a couple chilly weeks to come.
In March so far there have been five days below -2 degrees in Victoria when normally there would only be 1.1 such days, according to data from Environment and Climate Change Canada.
Temperatures from Victoria International Airport indicate this February is the second coldest on record, with a four degree departure from normal.
“What’s impressive is that the arctic outflow reached the coast and stayed so consistent all the way through the month,” said Armel Castellan, meteorologist at the agency.
The temperature signal in March, too, is looking very much colder than normal.
“The overnight low temperatures – those are gonna stay three, four, even five degrees colder than normal as they have for the past five days – and they’re slowly getting toward what’s considered seasonal somewhere in the second half of March,” Castellan said.
Flower counts this year are going to be “pretty interesting,” he noted.
The cold wave is relative to the polar air mass that leaked down south, also known as the polar vortex by media, which moved from the poles down into Canada and the northern part of the lower 48, Castellan added.
Usually a westerly storm clashes with the continental air with enough strength to displace the cold and “erode it all the way down to the lowest levels,” Castellan said. In this case, however, the cold was strong enough to shield off the low-pressure system.
Enough low pressure systems from the Pacific had come through, but they were only moderate in strength, he added.
The cold front was at such a stable pattern that, unusually, it stuck around.
“There were very small amounts of real Pacific air to clash with it – enough, obviously with all the snow that we saw in February, and that was still record breaking, but that was very little rain in contrast. Usually rain will still dominate,” Castellan said.
“But all told, they stayed as a snow event as opposed to snow changing to rain, which often on the coast is what we’ll see.”
Precipitation from the Pacific winds tends to form as rain when the Arctic front reaches the coast. Areas like Tofino and Port Hardy get hit the hardest on the eastern side of Vancouver Island, whereas Victoria is shielded from the southeast and southwest, where the Olympic Peninsula blocks approaching clouds, Castellan said.
Projections looking into future years and decades are still being talked about at the scientific and academic level and has yet to be concluded, but “nothing is really changing looking forward,” he added.
“At least the concept is there for people to digest and to understand that things like a drought patterns that we’ve seen on and off, mostly on for the past five summers, is also a similar impact of slacker jet stream.”
We’re now seeing the weakened jet stream in the winter time manifest itself in what is maybe counter intuitive – colder temperatures even though our overall temperature trend is warming in the last half century or so.