November 2, 2021
As we press towards the winter season, the signs of what may lay ahead can often be seen in overall setup of the global SST(sea surface temps) anomalies. That is in constant flux. A mainstay for recent years has been the warm AMO https://www.aoml.noaa.gov/phod/amo_faq.php
around 25 years into the cycle.
The areas of warm vs cool areas in the Atlantic have progressively became mostly warm
the warm anomaly area off the immediate SE coast of the U.S has not changed much in the recent decade. That often leads to a constant SE ridge trying to feedback and build. That sometimes sits in close building the ridge over the SE U.S and sometimes it builds far enough east it allows for cold intrusions to hit and stay awhile. Overall that’s been a bit of a rarity without other strong factors overwhelming the pattern.
One of those factors are the configuration of the SST in the north Pacific. A good sign for the eastern U.S is usually a cold pool at 30-40 north east of the dateline. With warmer than normal waters from the Pacific NW stretching up towards Alaska. That often will pump the ridge there and dump cold into east. If both features are strong, it’s often a battle.
Last year we had a weak La Nina, that was accompanied by a warm area along the Pacific Coast and stretching towards Alaska. That appears to be a rarity to accompany a La Nina. That’s why last year temperature pattern was not La Nina like. Least in my opinion.
That did not give the typical La Nina look of temperatures.
that was the winter reality, that while we remained mostly on the cold side locally, the SE influence while there, was far enough SE to not pump up the warmth, it did resist a few frigid blast mid winter. In the heart if the coldest vs averages last winter was the exact spot NOAA had predicted the greatest risk warmth
That’s night and day different from reality and to much of factoring the weak La Nina.
This winter is shaping up more like a typical La Nina. So far for Oct a recent glance says, 2007 La Nina looks similiar
the warmth 30-40 north east of the dateline, cold PNW into Alaska , warmth along the Atlantic seaboard that’s even more dominant now.
October of 2007 temps looked like this
October of 2021 temps looked like this
that’s a pretty similar look.
November did turn chilly along the immediate eastern U.S, and once we dove into December the SE ridge was flexing
by December the SST setup slowly evolved to a less extreme version
the latest 7 day SST change has seen changes in areas that help
that doesn’t overcome yet the features already in place and evolves over time, not overnight.
How the NE Pacific holds, evolves and the SE ridge are likely more dominant factors than the La Nina which still plays a role. My take on the winter
December is a fight. Cold intrusions, but a fight again with the SE ridge. This often leads to mixed events. Ice in Garrett County, rain Wv high ground, back end snow. Cold a few days before a push of Pacific air and the next system lifts out to our west dragging ahead mild air aloft, cold enough underneath for a mix, to rain to snow repeat.
January continues the fight early before settling into winter for a few week into mid Feb. That SE ridge though is always lurking to build. Often March fights back when warmth pushes in Feb as seasons begin to transition and enough cold around that most years see hits yet in April, and even a day here and there in May.
Long range is so complex, I do not think there are experts on it. Lots of great observers of the past, that make great connections that do not always play out the exact same. As for our start here, 2007 looks similar, but how we evolve going forward, there are key components that currently do not support a favorable cold snowy winter. That doesn’t mean there are not good cold snowy periods and it doesn’t mean we avoid any extreme cold shots.
if I was a gambler, I’d throw a small wager on this type of pattern with a touch more warmth overall in the east
but here’s to hoping things evolve in a more favorable manner across the Pacific and Atlantic and this is way off.
Allegheny Mountains Weather 