Strong polar vortex keeping us mild
Published 1:18 pm Saturday, December 4, 2021
By Skip Rigney
Early morning minimum temperatures near 50, although also warmer than the climatological normals of the lower 40s, were cool enough to cause fog to form in the relatively moist air which has been in the lowest layer of the atmosphere the last few days. However, each morning, bright sunshine steadily warmed this same layer, burning off the fog within a few hours after sunrise.
The immediate cause of the mild air, fair skies, and overall pleasant weather has been an area of high pressure along the northern Gulf Coast. However, a trough of low pressure and a weak cool front will approach the Gulf South from the northwest on Sunday night and Monday. Although the front should pass through the region, it won’t go far. Thanks to the front’s proximity, combined with follow-on waves of low pressure in the upper atmosphere, we can expect the upcoming week to feature a lot more clouds and higher rain chances than this past week.
If you’re waiting for a significant cool down to get in the holiday spirit, you might want to rethink that strategy. The really cold air on the weather map remains bottled up near Santa Claus’s house. Wind speeds in the river of air in the upper atmosphere known as the polar vortex remain very strong. Usually when the winds of the polar vortex are most intense, the vortex remains nearly circular and stays put over the Arctic.
It’s when the polar vortex weakens that it begins to wiggle and meander. That’s when large chunks of cold air break free and plunge southward. But, none of the computer weather models indicate any such southward excursion of Arctic air over the U.S. through the middle of December.
That’s in keeping with the Climate Prediction Center’s outlook for December, which they issued on Tuesday. CPC estimates that the southern tier of states from New Mexico to Georgia has a 70 to 80 percent chance of having a warmer-than-normal December. CPC’s long-range outlooks regarding average temperatures and precipitation from six days out to three months are available online at www.cpc.ncep.noaa.gov
At the end of October, CPC indicated that Mississippi was leaning, though not strongly, toward a warmer and drier than average November.
The drier prediction certainly came to pass, as most places in Pearl River County received less than an inch of rain, a mere one-quarter of the average of the last thirty Novembers, which is the climatological period of record usually used for comparison. The average temperatures for the entire month of November 2021 throughout Mississippi and Louisiana turned out to be near or slightly cooler than the November climatic average.
Unless the polar vortex weakens and allows arctic air to spill south, it looks like our December 2021 averages will end up being considerably warmer than what is typical for our first month of winter.
You might want to consider a tropical theme for this year’s holiday decorations and activities.