Winter forecast: Mild with chance of ‘profound’ episodes

Pete Parsons (Oregon Department of Forestry, meteorologist): Hey, I’m meteorologist Pete Parsons with the Oregon Department of Forestry. If you’re new to this, this is the three-month seasonal climate forecast.

This is an analog-based forecast. I look for years in the past with similar tropical Pacific Ocean temperatures to the current year. I see what happened those years and use that to predict what will happen this year.

Again, we’re just trying to give a general outlook for the three-month period, and this forecast begins where the dynamic models—which do quite well out to about 10 days—start to fade.

So we’re going to start this forecast in November, and it will go through January.

A strong El Niño has developed, and it could be the strongest one on record, which goes back to 1950, which makes sense because the global temperatures have been warming since then. So why not have the strongest El Niño?

And that we know affects the jet stream pattern globally in certain ways. We also have a cool phase of the ‘Pacific Decadal Oscillation,’ we call it, where the warmer waters are out in the Western Pacific and it’s cooler relative to average along our coast.

Those two don’t tend to couple together very often, so I have very few analogs to work with, but they’ve been performing quite well—and very accurately predicted the cooler, wetter weather that we had we transitioned into in September.

How about that? If we’d have used years that were in the warm phase of the Pacific Decadal Oscillation, they would not have predicted that.

So I’m sticking with the analog years that gave me the good forecast. Those analogs were ’71-’72, ’81-’82, and 2022-23. Going forward, as we go into November, December, January, it’ll be the winter of 72-’73, ’82-’83, and 2023-24.

Over the past couple of seasons, couple of years actually, we went from a weak Niña to ENSO Neutral, then back to weak La Niña last winter up through neutral, and then, boom, all the way up. Now we’re into a strong El Niño.

It’s really made that—that jaunt of warming here in the last few months. And the three top analogs track fairly closely, not perfect. None of them are as warm as what we have right now, but they’re all going in that general direction, and they all ended up in the strong or very strong El Niño category.

And they were either neutral phase or cold phase of the Pacific Decadal Oscillation. Tough to find years that do that. Those are the ones that are doing the best job analoging the associated jet stream patterns with this.

We’ve quickly moved into the strong El Niña, but we still have the cold phase, and that’s where there’s some, you know, some battle going on, and that creates a whole different set of weather patterns.

Not completely different, but it does open the door for some things like the cool wet September that we just had—found the closest matches here with the Pacific Decadal Oscillation.

So again, nothing is perfect, nothing is exact, but these are the best three years I could find and they’ve been performing well, so we’re holding them. No changes for this month’s forecast.

Here’s the current September, which again has developed into El Niño faster than the analogs did. We talked about the global temperatures and how they’re changing. They’ve been going up.

This measurement of the lower troposphere, it’s a pretty good measure of the heat balance going on in the atmosphere. It’s down near the surface, not on the surface. So it takes out the urban heat island effects, and it shows a general increase.

And we’re seeing an uptick right now. We had dropped with back-to-back La Niñas. Now we’re in El Niño. We’re bouncing back up. That’s very predictable.

But it’s been going up at about 0.16 degrees centigrade per decade since the satellite measure, which is a very short period of record, but it does add air to this forecast, and I’m taking some analogs even back in 1972.

So I compare those years with their respective 30-year normals. That’s what I bring forward. That helps take into account some climate change using those three years.

Here’s the forecast: A split flow pattern into the west coast of North America with a lot of energy cutting down toward California. That’s a classic El Niño pattern.

That’s why they’re expecting a lot of storminess down in California. They’re bracing for coastal flooding and beach erosion and that kind of thing. We get some of that. If we get a strong enough El Niño here, we could see some of that into Oregon, like we did in the—we had a lot of beach erosion in the winter of ’82-’83, and maybe that happens again this year.

We’ll see. But it tends to be a fairly mild pattern for Oregon. Temperatures not that far from average, maybe a little below in southern Oregon, maybe a little below everywhere, but not much.

But generally a little drier than normal. Maybe a little cooler than normal in November

For December, the ridge shifts a little farther east, the mean ridge position a little farther east. We have a little bit more troughiness than normal over us, but it’s a kind of a splitty onshore flow, so it tends to be more mild with storminess going into California.

Here’s the deal with the cold phase of the Pacific Decadal Oscillation again, that North Pacific ocean temperature cold phase and warm down near the tropics. The years that did that can give us one cold Arctic outbreak, either December or January. But otherwise it tends to be mild.

So we’ll see how that plays out. If we don’t get an Arctic outbreak in December, we’re going to be warmer than normal. If we do, we’re going to be colder than normal, or especially if we get one, like ’72, we’re going to be way colder than normal.

Precipitation? They varied considerably. So forecast confidence drops in the precipitation forecast. 2023 was dry, ’82 was wet. That lowers confidence. That’s all I can say on that one.

January: The mean ridge position propagates eastward, now just east of Oregon by like Idaho, right on the Oregon-Idaho border for the mean ridge position with energy coming into the west coast, but tending to split.

Tending to have one branch of the jet up here, one branch of the jet down here—storminess for California, perhaps into Oregon at times.

Maybe a lot of cloudy, drippy days. That’s what the analogs tended to have, so a lot of days with rain, but not necessarily a lot of rain overall.

And same thing with mountain snow. Temperatures tend to be mild. There can be Arctic outbreaks. 2024, ’23-’24 had an Arctic outbreak, lasted about five days. It was cold in the northern, got some pretty cold air up here on the northlands. Little bit of snow with it, but the rest of the month pretty mild.

So the general trend is mild. And again, the general trend for the winter is a mild winter, except for some brief episodes, which could be rather profound.

No big departures from average on the precipitation.

Three month period: Ridging along the West Coast, split flow pattern. General troughiness over the area, but again, most of the energy going into California.

The three-month pattern tends to verify better than month-to-month, ’cause those little blips, you know, who knows what month they’re going to be in, like a cold outbreak.

But overall, no major departures from average in the three-month temperatures or precipitation.

Your feedback is welcome. You can give me a phone call or an email and I’ll be happy to get back to you and answer any questions.

In the meantime, get out and enjoy some of the wonderful fall colors. We’ll catch up with you next month.