Stormchaserchuck1

I expect a warmer than average Oct-Nov, as the PDO has really high correlation in these months for above average CONUS. It even correlates higher than the PNA if you can believe it, and much higher than Nino 3.4 in the Fall, although both are generally above average.

I saw bluewave posted in the climate change forum, The Arctic circle trough that I had been tracking ended up maxing out at 4980dm yesterday, which is the lowest 500mb height on record in the Northern Hemisphere for August. It's akin to the 10" of snow that fell in Florida last Winter happening again.

^I don't think it's going to be as much of a blowout +NAO Winter as we previously thought, but there is still strong tendency for us to pattern change 10 days to a few weeks after a cold period, that has been in effect for a while now. I don't see 13-14 style cold happening this Winter. -NAO/-AO/+PNA hasn't been staying in a strong state for more than a short time. Last Feb it went from -31F in Valentine, Nebraska to 60s a few days later. Some places had a 3-day change of 100 degrees. It's not sustaining.

Actually the cold waters off of New Foundland have turned my N. Atlantic SST indicator for Winter NAO negative on the daily. Of course, it's an average of May-Sept, but Erin really did cool that -NAO area a bit.. if you want to make a correlation between ACE and following Winter NAO, like a lot of people do... It's been pretty rare lately to have that whole area from the Davis strait to N. Atlantic below average, but there has been persistent -H5 over the region this Summer. I've found that since 2012 it correlates with a following Winter ridge at 90N.

^Yeah the Great Lakes trough for around 9/4 was not even on models 7-10 days ago. Now it's expected to be -400dm and actually closes off for a little while. I've been noticing weak projections on ensemble means >11 days out. I wonder why that is.

Interesting that the pattern usually flips one year after a 2nd year La Nina minus 2nd year El Nino (Winter 26-27)

Another trough hitting the Great Lakes around 9/4.. it will be interesting to see where we go after that, it might start warming.. October is the month of the year where the PDO correlation really picks up, and is the highest correlated PDO month of the year, in terms of non-0-time based happening: But in September the PDO correlation is still weak

Nice post. I love subsurface data, as the thermocline probably has a better correlation to our pattern than surface SSTs, which are variable from the pattern (look at how much Erin cooled SSTs). Subsurface data is spotty, so any info on that is great info. That updated image to July 2025 is cool. I would think in a more classic -PDO it wouldn't be as warm from the top down, and you would have more consistency about 200m deep. I've always said I think it's more of a decadal La Nina state in effect.

Highest daily SOI today since May.. +24. I think a Weaker La Nina state is more likely for the Winter. 2nd year La Nina's and -PDO's tend to have a more classic cold season -PNA pattern, but we haven't had as strong of a -PNA generally since the 23-24 Strong El Nino. It's very likely that August 2025 will be the 11th consecutive month with +SOI Top 20 best matches since 1948 to 2nd year La Nina vs 2nd year El Nino for the cold season (Nov-March) Dec-Feb

505dm over the Arctic circle today! It phases into a +NAO/+AO in the next few days, which is usual for the pattern this year since May. Cold +AO/+NAO H5 continues..

I'm so interested to see if we get a cold December this year, because strong -QBO/weak -ENSO analogs strongly support it. I remember those similar 2 conditions in the Fall of 2005, we used the 1989 analog, and it worked out great that Winter. Besides that, there is nothing strongly anomalously warm about the global pattern right now, wrt to previous years. I am going to be in the 70s for highs something like 13/14 August days, which is unusual. We had a warm up in June, but cold H5 was overtop of it, so it was a strong +NAO driven warm up. We aren't just popping ridging out of nowhere, like we did a lot 2020-2024. For all this about 2nd year El Nino's being so warm in the global pattern, you don't hear much about 2nd year La Nina's, and the cooling effect. I think since late November last year it's been a cooler US pattern, relative to global warming and all. Will be interesting to see if it lasts into the Winter. Analogs say that odds are starting to become in that favor, the more we get these cooler patterns through the Fall.

Sub 5100dm over the Artic circle tomorrow! Areas of cold 500mb >60N continues to be a theme for the warm season since May 2024, and May this year. I say for cold Winter prospects, give me cold upper latitude 500mb earlier in the year. I think it correlates to more -EPO conditions down the road. Hopefully the trend of cold 500mb continues in the Fall. It shut off after September last year, and in the Fall of the last several years.

Pretty cool to watch the N. Pacific warm pool shift north with the Summer pattern. It's aligned right now with the Hadley/mid-latitude Cell.

^Winter NAO prediction based on May-Sept N. Atlantic SSTAs will probably come in weakly positive. Add to it that we are in the period of 0 to +4 years after a Solar Max, which has a +0.2 Winter NAO correlation, or 55% of the time. Then the NAO has run positive 6 straight months, and the AO has run positive 5 straight months.. that rolls forward to a +0.2 Winter +NAO correlation. All-in-all, that gives us about a +0.3-4 correlation right now for +NAO Winter (DJFM), or 60-62% chance of happening, based on those 3 indicators. Because of the decadal cycle, and 83% of Winter months have been +NAO since 11-12, I would say the current odds are more like 65% chance it is a +NAO Winter.

18-19 and 20-21 through 22-23 -NAO's were really not getting cold at all. The last 2 Winters, there has been cold under -NAO patterns in the east, and the Mid Atlantic has done better in those times.

Down below 5190dm over the Arctic circle Aug 22-25. It's doing exactly what that +AO roll-forward showed, in the exact location, albeit a few months early. I thought this was impressive because the Polar Vortex was 2000 miles from where the base +AO period had negative H5.

Down below 5190dm over the Arctic circle Aug 22-25

Thursday I will have been 75 or under for a high 4 straight days. Yesterday it didn't get out of the 60s. Hard to believe it won't be cold enough to snow in the Winter unless we stumble into a really bad upper latitude pattern. The cold next week (more days with highs in the 70s) is largely -EPO driven. Aug -EPO is actually a colder-Earth pattern, when you roll it forward into Jan-Feb the correlations are pretty high on the below average side generally I was stressing the cold H5 over Greenland May-July. It's moderated now, but has been proceeded with some cooler indicator conditions. Last year there was cold H5 over Greenland May-Sept, this moderated in the Fall.. this year it's the same thing but maybe 1 month early on the moderation. Give me cold H5 earlier in the year, I don't care if it's +NAO (unless it's the Winter).

A big problem has been the upper latitude pattern. This big ridge in the N. Pacific is -PNA Here's the Winter sea-level pressure pattern with PNA (map is default positive, so what's happened lately is opposite of this map) ^Notice the low SLP off the east coast. -0.3 is pretty significant correlation. We've been seeing -PNA (North Pacific pattern), so there has been more tendency downstream for High pressure along the east coast and off the coast. That's just the Pacific.. in the Atlantic since 2011-2012, 83% of the Winter months have had +NAO! In that time monthly NAO readings of >1.11 have been positive 18-0. Here's the SLP correlation with NAO, this map is default positive so in +NAO, like we have seen lately, it is like this Again, very High pressure correlation. Add the Pacific and Atlantic upper latitude patterns together and you have 5x more likely to have east coast, or off the east coast, High pressure vs Low pressure in the Winter months. That's the pattern we've been in since 2011-2012 and more so since 2016-2017. A core reason for this is the decadal La Nina state that has been in place since 1997-1998. Some say -PDO, but the Hadley Cells are flexed in the southern Hemisphere too so it's been more Nino 3.4 driven, imo. Atlantic NAO is a decadal cycle, since the 1800s there have been 4 swings between positive and negative. They usually last 30-50 years at a time. We have been in the middle of a +NAO decadal cycle. Of course the jet stream is moving north with global warming, but it's been bad timing with regard to long term global pattern fluctuations.

^It seems the Euro ensembles are good at those long range forecasted hurricane numbers. I remember in the 2nd half of last season they had 5x average, and we sure did have an active period.

I started keeping a weather journal in Sept 2002. I was surprised looking back at it, how many days there was snow in October. It seems those massive Winters hit early, consistently, and end late. My last snowfall in 03 was in early May, and it snowed over 100" that Winter. The odds of a major one is probably 5:1 less this Winter, while closer to average doesn't have as bad odds.. so yeah, October might come in a little warm (The PDO's top correlation month of the year is Oct).

Hard to believe we ever had -AMO, but for 100 years the Atlantic did average 9 named storms per year.. We are already on number 5 with moderately above average SSTAs. This is the 3rd year in a row with top 1% Rapid Intensification where a certain storm jumped over 12-18 hours: 2023 was Lee 2024 was Milton 2025 Erin I mean like 75mph to 160mph overnight jumps.

Yeah, two -PDO/Weak Nina seasons in a row with +PNA? That's what I'm thinking.. the PDO actually scores so high on long range predictability, and I found that when it didn't work one season, it worked the next season at 1.24x the average. Anyway, energy traders are hedging on a warmer Winter bet over the last few weeks. Natural Gas December contract dropping from $4.80 to $3.70 over the past few weeks.. despite -PDO rebounding a bit.. that's a bet on more +NAO conditions this Winter.

Again, with -ENSO (persistent +SOI), -PDO, -H5 over the Arctic during the Summer, I'm liking a blend of the last 5 Winters (20-21 to 24-25). We should at least get some cold shots, I don't think it will be a wall-to-wall warm Winter, like 97-98/01-02 or anything like that. 22-23 had some -EPO/-NAO patterns in Dec and March that didn't deliver, I'd take my chances with the same upper latitude pattern.

Philadelphia's previous 7-year low snowfall record was 13.2" The last 7 years has been 10.5".. they might be the epicenter. I know that I haven't had a storm over 5.5" since Nov 15, 2018.