El Nino GRANDE
The El Nino that has arrived is a monster and its still gaining intensity quickly already it has entered record territory with some parts of the El Nino zone at 3.4C above the norm. Thats frightening as it will not peak until winter and possibly spring. I’ve waited as each new El Nino forecast has been released. And if what you have been hearing about the coming winter is confusing is because it is confusing.
Meteorologists are looking at all oceans- not just in the Pacific equatorial zone that have been at record warmth. This years El Nino starts from a much higher baseline. And addition to that and the amazing amounts of heat being released by El Nino it is not following typical patterns and so the forecasts have been changing quickly as this remarkable El Nino intensifies.
Another *ucking weather acronym- PDO
Its important to know that another more long term ocean heat phenomenon is playing out the Pacific. The Pacific Decadal Oscillation (PDO) is broadly a warming of the North Pacific that occurs every 20 -30 years. In 2020 that phase flipped to negative . What that means is there is huge area of warm water, that is also being reinforced by El Nino that is covering the whole far North Pacific. Ocean heating is on overdrive.
A turbo charged El Nino has thrown all these systems out of whack. Forecasters are trying to make forecasts using scales that are so extreme they’ve had to extend their graphs to numbers they have never used and had to find new colors for their forecast maps- the knock on effects of a Mega El Nino changes the game entirely. Unlike previous El Ninos where warm water banks up against the west coast. This year that area remains cold. The warm water from the North Pacific marine heat wave has moved to the west and warm water is pooling south of the Aleutians over to Kamchatka and Japan. This does two things it causes an area of high pressure over the warm water. This semi-permanent ridge will extend over Alaska and that perturbs the polar vortex.
The Polar vortex is like a jet stream of extremely cold air that circles the poles 30 miles up in the stratosphere. Normally this vortex is kept in place by the jet stream and it traps cold air around and over the poles. If that vortex gets perturbed and a ridge pokes up, you can get what is called a sudden atmospheric warming event. This is very warm air that is sucked towards the poles and it pushes the polar vortex out of whack and that dam of cold air is broken. Cold air comes crashing south. Sometimes VERY far south as in the Texas Freeze of 2020.
We should watch for cold air this winter.The door could swing wide open
If you know how cold spells evolve in the Pacific Northwest, the semi-permanent high over Alaska normally shoves cold air east of the Rockies and into the East. Thats the scenario most winters and one of the reasons we have infrequent bouts of truly arctic air. Everything depends on the placement of this ridge. This time it will be centered over the west Pacific rather than the eastern Pacific. And this kind of ridging will open the door to a path for arctic air that is farther to the west, down the coast into the PNW and especially the inner northwest. This large ridge placement will also perturb the polar vortex which means it could wobble south or break apart and a piece could slide south creating a cold air outbreak with an unbroken path directly over the PNW, then the vortex would reform and there would be stretches of rather bland, mild weather. And that part checks out. Normally during an El Nino winter in the PNW a weak area of high pressure off the coast splits and weakens storms, there is a lot of partly cloudy weather and extended periods of valley fog. The forecast is for a dry bland, mild winter, possibly punctuated by a bout or two of possible arctic air. Thats not very reassuring and it shouldn’t be.
Long stretches of mild with a constant eye to the north
El Nino in the PNW especially mild to strong El Ninos seem to give us a milder/drier winter. That is for the winter overall, short intrusions of arctic are almost always smoothed away by averages and though they do happen they tend to be brief and shallow . A mega El Nino is not following those rules. Though its not uncommon for an arctic event to occur during an El Nino this years set up looks like something we should watch closely. The past two winters have been exceedingly mild (ultimate lows were 25ºF, 22ºF) respectively and so the odds of an arctic event were already heading up.
Wetter for us?
Also, the latest forecasts have the energized jet stream that heads into California may not just stay there, they are now showing above normal precipitation all the way to Southern and Central Oregon. That is good news because those areas have suffered a years long drought. If this interacts with cold air the ski season might not be facing as dire a forecast as they thought.
An energized jet stream moving to the south also means that the whole southern part of the country will be wetter than normal and if there is a pathway for arctic air to interact there is the foreseeable possibility of large snow and ice storms threatening farther south than normal. This has already been noticed by utility companies and occurred during the last super El Nino of 2015/16 with record breaking snowstorms east of the Mississippi.
Preparations- just to be safe
So: we will likely have an above normal winter overall that is slightly drier. It could be punctuated by a cold outbreak, keeping our eyes on the the Alaska High, hint if you see meteorologists using the words retrograde (moves west)of the Alaska High prick up your ears that is a sign that the arctic door could open. The area of above normal forecast precipitation has moved north and into south and Central Oregon. Which is good news. As a gardener I would keep mulch, burlap, cardboard boxes at the ready. And the forecast overall seems to point to winter beginning in earnest Jan- Feb. That is prognosticated to be when we have our most active weather, the second half of the season.
If there is an arctic event in our future, we will of course be paying attention and pass along any information.I have a feeling a snowstorm/Ice storm or two and lows of 15ºF will pale in comparison to what the rest of the planet will endure. This is a year to mulch in the fall.