Stormchaserchuck1

La Nina effects on the Winter Northern Hemisphere pattern actually puts a High pressure over the North Pacific High, which is just off the west coast of the US. A lot of people think its main effect the PNA, which is actually only the case for extreme west-based events. Last Winter despite +PNA we did see a +NPH pattern. It was Weak-Nina like. I think we could be looking at a similar pattern here, at least to start this Winter, going into November and early December. Beyond early December, I wonder if the now neutral ENSO subsurface will make the La Nina less impactful. If the SOI stays strong through next month (it's been positive now 15 months in a row), we could see more a of a east-based La Nina like composite for the Winter, which is usually cold in the Upper Midwest and sometimes Great Lakes. La Nina December's also have a tendency to be cool in the Upper Midwest, Great Lakes, and Northeast - that's if the SOI stays moderately positive through next month and December.

30-day SOI is now the highest it's been since Feb 2023.. almost 3 years. Now long range models for the 2nd week of November are showing a +NPH (North Pacific High), which is more of a La Nina pattern (+NOI).

It used to not be uncommon to see snow flurries in October.. we aren't seeing anything like that, but Aug 1 - Nov 5 is probably going to be the first time we've been below average for the time period in a while, possibly since 2013.

The troughy pattern really turns into a +NAO out here pretty quickly With it being just after a Solar Max, I do think more +NAO is favored this Winter.

If I were a farmer in the 1800s, looking at sensible weather lately, I would go for a colder Winter. In August it got cool.. I had something like 15/16 days where it didn't get out of the 70s in August, and it's stayed relatively cool through September, October, and it looks like early November. In the last 15-20 years, we have had a lot of very above average Fall's. At the least, I think a blowtorch winter is off the table. The pattern would need to completely change around for that -- we have a little more tendency for -EPO right now.

The NAO is correlated with changes in the AMO at about 0.4, or 70% of the time. +NAO cools the AMO, we saw this in Hurricane season 2024 when there was a lull of activity mid-season during record +NAO. Now since October is -NAO, and the NAO looks to be negative a good 4 weeks, they are saying the AMO is changing. A better way to do that, is just roll forward October NAO, which does not actually have a positive correlation with Winter NAO. Every October has been -NAO since 2019.

Here is what we get the Winter before an El Nino the following year

SOI has been positive now 15 straight months.. -AAM the last few months, -PDO, a few things are lined up for cold-ENSO it seems, but without a big ENSO subsurface cold pool it's going to be hard to get N. Pacific -PNA. The subsurface cooling could come back, it waxes and wanes, but the way it looks right now is pretty far from La Nina analogs.. Crazy thing, although SOI has been positive 15 straight months, it has never gone above +10.. so we've been consistently on this weak-cold ENSO thing. I think the past shows us that when that happens the odds for a future El Nino increase.

Halloween now looks very cold. A few ensemble members bring the 528dm into the Northeast.. there is a pretty good spread and variation for that trough on current models though.

I think this Winter might just act ENSO Neutral.. a lot of different patterns. I do think we'll see more +NAO but probably more -AO. December has this high coincidence being very, very cold in neutral-negative ENSO/deep -QBO. I want to see if that coincidence persists this year.

I think last Winter was the most +PNA on record for a non-El Nino (CPC).

RONI does have 2-3x more impact on the pattern in the cold season. I'm really curious if we get more La Nina tendencies this cold season, seemingly out of nowhere, as that's what a few things seem to suggest. I'm not sold on it.

Yeah part of it too is that we haven't seen anything La Nina like in the N. Pacific this year. It's acting Neutral ENSO. Also, the subsurface moves up and down a lot in a short period of time.. remember how I was congratulating Gawx for La Nina calls because the subsurface had made it <-5? Now it's come all the way up to 0! Depending on MJO waves and gravity waves, it moves around a lot.. I don't necessarily know that it won't turn negative again, as that is the base long term state right now.

See how we are getting this +PNA over the next few weeks now that the ENSO subsurface has neutralized? It's not perfect but more times than not how it fluxes connects with PNA (Kelvin/Rossby waves).

In the last day +0c has hit 140W. That is significant. The central area is most important for N. Pacific H5 correlation.