Winter is starting to look interesting.

 

We've started meteorological fall Which means Winter is getting closer.

I've been posting these little  winter thought for the last couple of months This is something I'm probably going to continue to do. so This will be a large part on how the winter outlook work this year.

Over much of the summer, there was a lot of heat with several heat waves impacting our region. But for the last few weeks we have been coolish here in the Northeastern and Middle Atlantic regions of the US.

The reason for this Has been the ridgeing we've seen over western North America and  troughing over the eastern half. This has allowed cold air to drift out of Alaska and northern Canada And fall into the US. 

The polar vortex:

The polar vortex is a large area of spinning air (Vortex) that spins over the north pole. Typically spins in a counter clockwise direction, making it generally stronger. It typically weakens a lot during the summer and then reemerges as we get into fall, right around this time of year. The polar vortex has a big impact on our winter into spring pattern.

When the polar vortex is strong It typically locks out the cold arctic air over and around the north pole. But when it gets weaker We typically see a lot more variation In the portal vortex Which leads to outbreaks of cold air dropping into the lower latitudes.

What's going on with the polar vortex right now?

We've had warming in the stratosphere the last few months. This has kept the polar vortex weaker this year, as it interfered with the overall pattern.

The Quasi-Biennial Oscillation (QBO) is currently negative, which is causing the stratospheric winds to be easterly. This is also helping to weaken the polar vortex; as it reverses the direction of the polar vortex thereby causing it to weaken.

Sea Surface Temperature:

Current global SST's

Global SST's For August 2024

Image credit Tropical tidbits

Comparing last year's and this year's SSTs in the North Pacific. We can see this year they are much warmer than they were around this time last year. We can also see that the SSTs in the eastern into central pacific are much colder than they were at this time last year.

Where those warm SSTs around Alaska we're likely going to see a persistent strong ridge that's going to develop in the Northeast Pacific. This would lead to a likely stronger polar jet developing. Which would help transport some of that cold out of Siberia Into North America. The winter of 2024 experienced a strong North Pacific jet. Does help to lock some of that cold up in the Arctic. Because of those warm SSTSs around Alaska That northern pacific jet might not be as much of an influence on the North American overall pattern this winter. This could help promote more cold outbreaks then we saw last winter.

El Nino Southern Oscillation.

We are still under an official la Nina watch.

The ENSO prediction models are showing a weak La Nina heading towards winter 2025- 2026. Then as we get into winter we would see the ENSO revert back to a cold ENSO neutral state. A weak La Nina or a cold neutral ENSO would imply a colder winter ahead

Temperature anomalies for ENSO neutral winters

This is showing a strong likelihood for generally overall below average temperatures for the upcoming winter.

The Eastern Pacific Oscillation (EPO) and the Atlantic Oscillation (AO) are going negative. This is also A cold signal  not only for this fall .But it also shows the pattern Heading into winter could feature high pressure blocking and more cold outbreaks

 Image credit Weather bell 

The first half of September is looking to be quite chilly with below average temperatures.

Image credit Tropical tidbits

The Climate Prediction Center (CPC) 6-10 day temperature outlook does support this idea of cold over the eastern US.

This general troughing is going to stick around across the eastern continuous US at least for the next couple of weeks.

2 meter temperature  anomalies

Image credit Tropical tidbits

That above average high pressure sitting over western Canada. Is going to create something rare for September, we're going to see a cross polar flow direct colder air into the eastern half of the United States. A cross polar flow pattern is something we normally see during the winter; The reason for this is typically our pressure systems are stronger during the winter than they are during the summer.

Looking at the temperature anomaly map we can see western Canada sitting under the high pressure ridge. This helps direct that much colder than average air down into the central, southern and eastern United States.

Looking at the extended range on the GFS, the same overall general pattern of high pressure ridging out over western Canada and some troughing in the eastern US looks to continue. Extended range models tend to average out everything the further out you go. So they kind of mute the overall look of the pattern. As we get closer the ridge and trough effect could become more profound. I don't think the second half of September is going to be as overall chilly as the first half, here in the Northeast and northern Middle Atlantic.

Image credit Tropical tidbits

The polar vortex is very weak right now. In fact It's at record weakness for this point in September. With the vortex so weak, we could see a lot of variations leading to cold air outbreaks as we head towards meteorological winter which begins on December 1. The pattern does favor frequent cold fronts moving across the CONUS. So fall 2025 could feature more than a few cold outbreaks as we move forward. What does this overall pattern hint at for the upcoming winter?

Current thoughts about this upcoming winter:

With the polar vortex Start now fall so weak It's implying at least to me that we could see a highly variable polar vortex During winter 2025-2026. 

The upcoming winter is looking to be quite variable, with the northern half Of the US averaging quite cold and wet, with the southern half of the US being very mild and dry. 

If this does end up being the case it could mean the Ohio Valley, across southern Pennsylvania into southern New Jersey, Maryland and Delaware end up being in the battle zone with an active storm pattern. The risk for ice storms across this part of the region would be much higher than average.

The current setup of the pattern and the way it's looking to evolve Means this winter could see quite a few Clippers.

We could see more in the way of Nor'easters than we've seen in the past 5 or 6 winters. 

This would imply that Maryland, Delaware, New Jersey, Southeast Pennsylvania up through Southeast New York state, across southern and eastern New England from Boston to Maine would have a good chance for a very active winter.

The pattern that looks to be setting up looks to be very favorable for lake effect snow. Like last winter, the lake effect snow belts could be pummeled by quite a bit of snow.

The first half of winter (December into January) could be a bit mild. Then the second half (February and March) could be very cold and stormy. Because, winter could start with a predominantly positive NAO and ends with a primarily negative NAO.