If some meteorologists are right, Santa Claus best beware he could be on thin ice when he gets home from making this year’s deliveries.
The polar vortex is decaying again, they say, and a lot of cold air could be about to leak away from his northern homeland.
With snow covering the gondolas in Venice, the news was bad for both regions, but people being people worried first about themselves. This being the Christmas season,we might give a little consideration to the icy kingdom of the merry, old elf.
That done, we can now start wondering about what to expect in Alaska.
Because if the past is precedent, all that cold, polar air sliding south from the Arctic into the middle of the North American continent is likely to bring a strong push of warm Pacific Ocean air into Alaska.
“The best analogs for the upcoming event, at least based on the Canadian and the ECMWF (European Centre for Medium-Range Weather Forecasts) forecast are January 2003 and February 2010. Those happen to be El Niño winters similar to this winter,” predicts Judah Cohen, an MIT climatologist and director of seasonal forecasting at Atmospheric and Environmental Research (AER).
January 2003 was about 4 degrees above normal in Anchorage, according to the National Weather Service. February 2010 was just shy of 7 degrees above normal in the state’s largest city, according to the Alaska Climate Research Center.
Warm winters both, neither was anywhere near as crazy as 2014 when the polar vortex fell all to pieces. This is the 2014 summary from the National Weather Service:
“January 2014 was the warmest since 1985 and the fourth warmest in the past seven decades….Several long-term climate stations in southern and southwest Alaska recorded their warmest January ever, including Homer, King Salmon, and Cold Bay.
“At Anchorage the average temperature for January of 29.4ºF was the fourth-warmest on record—slightly warmer than the average temperature this past January in Philadelphia and New York City! At Nome, the temperature rose above freezing on 14 days, the second highest number of above-freezing days in January.
“A number of locations registered the warmest temperature ever recorded in those areas during the month of January, including 61ºF at Seward, 57ºF at Homer, and 40ºF at Kotzebue. While there are no long-term observations at a single location in the Palmer area, the high temperature measured at Palmer Airport of 58ºF far exceeds any reliable temperature ever recorded in January in this area.”
The predicted thaw this time is expected to be significantly smaller, but weather forecasters all note the huge degree of variability that has emerged in the wake of these weather events in the past.
“…There’s uncertainty. No polar vortex weakening event is exactly the same,” writes Jonathon Erdman at The Weather Channel, which is predicting “The Polar Vortex Might Weaken Soon, and That Could Unleash a Much Colder January.”
That would be a colder January in the Lower 48.
When the rest of the country zigs, Alaska zags because of the interactions between the jet stream and the vortex. A stable vortex over the pole keeps the winds high aloft generally spinning west to east around the ice cap.
And it turns, turns, turns
Without the vortex to keep the lid on things, the National Oceanic and Atmospheric Administration (NOAA) says, “the jet stream doesn’t have much to keep it in line. It becomes wavy and rambling. Put a couple of areas of high-pressure systems in its way, and all of a sudden you have a river of cold air being pushed down south along with the rest of the polar vortex system.”
As the river of cold, Arctic air starts flowing south into the midsection of the continent, another river of warm, moist air starts flowing north from tropical Pacific Ocean into Alaska’s gut.
Cohen analyzed northern hemisphere surface temperatures for two weeks immediately following the dates of major, mid-winter warmings similar to the one now expected and tracked them for the following three to six weeks or until end of the winter. There were eight such events between 2001 and 2018.
In seven of the eight, most of Alaska warmed. In four out of the eight, all of the state warmed significantly, sometimes by almost 10 degrees.
The U.S. Climate Prediction Center is now saying the January “temperature outlook favors above normal over Alaska” with “above normal precipitation…also favored over the southern third of mainland Alaska, which is consistent with an El Nino, though this is not predicted by all models.”
Given that January and February temperatures in Alaska are normally well below freezing, the precipitation is likely to come as snow, which will be good news for snow-sport fans.
The above normal temperatures not so much. Anchorage was almost 8 degrees above normal in November, and 10 degrees above normal in October.
As a result, lakes and rivers have been slow to freeze. Two Anchorage residents died Dec. 18 after their snowmachines went through the ice on a lake north of the city popular for recreation, reported Alaska State Troopers, who were warning riders to be alert to thin-ice dangers.