Quote:
Originally Posted by Resident 2B
One of the larger gears, the Artic Osollation (AO), is forecast to go significantly negative and at the same time there is a ridge building across the Artic Circle from Alaska to northern China. The negative AO will allow the pool of Artic air to expand southward and the ridge will push more of the cold air over towards this side of the planet. The NAO trending negative will help some as well in channeling the cold air into the northeastern US.
All of these will be big players in the real winter weather just ahead. Enjoy it while it is here.
R2B
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Some are probably wondering what this means. Imagine the top of a candle (lit.) Wax melts down the candle, but not evenly. That's the way cold air "drips" away from the poles. Notice I said "away" rather than "down" because at the South Pole the cold air drips "up."
When one of these gears of the polar region "goes negative" or "goes positive" it usually means (visually) that the location of the 'wax drip' is about to shift from where it is, to where it isn't.
We're all familiar with the big round world map with the Americas on the left and Europe/Asia on the right but if you look at a round map with the North Pole in the center and plot the weather pattern on it, you'll see the cold air (Polar air mass) in the shape of a sci-fi blob monster with multiple arms... or the same shape that would appear on your floor if one of your (grand)kids dumped a half-cured bucket of joint compound off a step ladder just to watch it splat.
The splat-mark forms a certain shape that wobbles around day by day (weather) but also week by week, month by month, and year by year (longer-term cycles.)
The blob is cold air. Where one of its "wax drips" (or "blob arms") reaches down, usually that's where the storminess is. That's because iit collides with the air in front of it (which is always lighter) and acts as a boat going through water -- creating a turbulent "bow wake" as it goes.
That's what causes most of our stormy weather, in the northern 2/3 of the US.
Within the bow wake of your boat on the lake, you may notice swirls the size of your hand. In the "bow wake" of one of the "arctic wax drips" there are swirls too -- and those can be several hundred miles across. If they get strong enough they'll suck in air from 1,000 miles away or more. If the Gulf of Mexico happens to be within reach, then the vast moisture supply from the gulf will get drawn into the swirl's circulation where it would get thrown into the side of the cold air. Throwing vaporized moisture into cold air is what snowmaking crews at ski areas do.
The feed of moisture ("snowmaking hose") stretching from the gulf into the center of the swirl is in the way of the "bow of the boat" -- the leading edge of the cold air drip. The leading edge ("cold front" as military weather forecasters named it) is heavy and moves along the ground the same way as a giant torrent of water would do. When this torrent of cold air (the cold front) broadsides the warm/moist feed in a T-bone type collision, the gulf air gets lifted up, by the same laws of physics that allow a fast-moving tractor trailer truck to launch a deer up & away (venison, anyone?)
This collision results in turbulent updrafts that are the foundation for all severe weather (t-storms, tornadoes.)
The swirl ends up with a moisture feed being blasted into cold air to form a snowmaking machine on one side...
...and the leading edge of the cold torrent "t-boning and lifting" the moisture feed to form big thunderstorms and tornadoes on its other side.
The parent swirl is happening within the "bow wake" along the leading edge of a drip. And the drip is one of many such extensions of the polar air mass, which is shaped like a splat mark.
If any feature of the splat mark lingers in place long enough and seems to shift about in a pattern, we give it a name and start predicting its movements. Those movements cause a lot of weather.