Stormchaserchuck1

You can see by my post above that the WPO tends to reverse for December, and sometimes January. In all the historical data, this reversal does tend to happen on different time scales. I think that we have seen 5/6 +WPO Winters, with one being neutral means it's somewhat unlikely to happen as a mean again this year. I think you have been intuitively saying this for a while.

The Summer Hurricane season has nothing to do with the Winter, except for larger macro factors that correlate both things. People use it because it's an easy data point, but sometimes you have to think about the physics of meteorology. Storm systems would have circled the globe 3x by the time the Winter is here.

The GFS ensemble mean now has a >594dm ridge over Japan in the medium range! I think this could be record breaking by a little bit. It's part of a strong +WPO pattern, which I said would be more likely to happen this October earlier in this thread (because of the Winter +NAO tendency projection and -PDO). This is how a +WPO October rolls forward to the Winter across the CONUS December January February January has a pretty good +NAO match.. which I have seen with a few different things, like -PNA conditions in September.. this could be the month where -PNA/+EPO conditions ease up.

Warmest the subsurface has been since early February

Nice 594dm ridge off the coast of Japan.. I bet we will be seeing some Twitter posts on this one What's interesting is that these super warm SSTA areas are preceding record 500mb conditions in the same area... We saw this over the Summer when the New Foundland warm pool got ridiculous.. then a week after that occurred, the Atlantic broke it's all time record for >600dm ridge right over that SSTA area. Now we have >10F anomalies off the coast of Japan, and weeks later, a record ridge is occurring right over the same area. Oct NAO is also starting to look negative on LR models, not coincidentally coinciding with +epo/-pna.

This one is already getting an eye

The MEI has been matching the ENSO subsurface until now.. I wonder how big the MEI/PDO correlation is? My guess is, because the N. Pacific pattern and enso variables don't react as strongly when the subsurface is neutral that it will bottom out pretty soon.

Likely below -3 now, and the H5 pattern has been matching the historical data perfectly.

Subsurface is neutralizing.. barely any -2's on todays map. If the SOI keeps going like it has been, the La Nina will run out of fuel.. Last 30 days is a mere +2.3 on the SOI.

It does appear to still be in a strengthening phase. Over the last 30 years, the Oct PDO has done admirably for predicting the following Winter's conditions.. I'm not a believer in SSTs being the main cause, but its correlation scores are really high. A lot of the cold years saw cold in October (highly correlated to +PDO), and a lot of the warm years saw ridging in October.. we are I think #2 lowest PDO right now since 1950. Oct 2013 was nothing like the progression being shown in current LR models, which fits PDO events almost perfectly (2013 was an example of the PDO trending in a direction in the Fall vs already being in that state)- Cold Winter was already showing itself at this time in 2013.

This looks more like a -PDO to me than La Nina https://www.meteo.psu.edu/ewall/ENSHGTAVGNH_18z/ensloopmref.html In La Nina, you get more interaction with the North Pacific High (+NPH) This is full on -PDO North Pacific High area is further East

The subsurface has been leading the surface +3-4 months for a while now. It started weaking a little over a month ago, and it seems the current trend is for it to moderate. The SOI never broke +4 for the La Nina event until recently. Even now the 30-day is only +3. Gawx has posted about how this factor is correlated to the surface. It also seems to be leading. The Fall is typically when ENSO events deepen, but I think in the Winter it may neutralize pretty quickly. We might not get 5 months of <-0.5 ONI for an official La Nina, but it will be close. Glad to see donsutherland posting more in this thread.

Actually, you might be able to kiss this La Nina goodbye.. those are some weak subsurface anomalies.

Yeah, maybe I will. I feel like a lot of what would be discussed has been posted in this thread.. will have to go back and put it all back together

Good job. Those H5 composites for the Winter looks almost exactly like mine would.

18z GFS initialized the Greenland block at >5820dm. Looks like a +500dm anomaly.

Why were the 1980s and 90s +PDO? We also just had a healthy +PDO not too long ago from '14-16. I don't think seasonal forecasts are doing bad.. the -PDO/Strong El Nino composite worked about perfectly for N. America last Winter.

PDO correlation is really working

There actually is a near neutral correlation, believe it or not. This is +1 year from a September PDO event: Winter PNA for 2025-26 is also actually near 0 to the following years Fall PDO (+14-18 months). It could also just be that the data is limited. I do think the ENSO subsurface cold pool orienting back west recently is a damper on El Nino chances for 25-26.

18z GEFS has an Aleutian ridge extending to Japan Oct 1-5. Pretty good chance this is a solidly negative PDO Winter (correlation is opposite, default is positive) Poor New Mexico lol

Some of these Summer patterns with warmth on the West coast do roll forward to a +pna/-epo chance for Dec and Jan. If we have a -PNA ridge, and I've talked to you about this before, a -PNA ridge due to the La Nina and -3 PDO, it may help the NAO go neutral to negative when that happens.. but I think if the +NAO is a strong signal, which it is, we may have some 10-day periods this Winter where the Pacific is favorable. most likely in Dec-Jan.

My NAO formula, based on data since 1948, says we have a 50% chance of having DJFM NAO 0.00 to +1.10 (per CPC calculations). Now lately we have had some Greenland ridging while the CPC calls it a +NAO, so the AO may have a better chance of being neutral to negative. But that's a pretty high SD for at least a moderately positive NAO this Winter.

I think that the progression favors a +NAO Winter.. It works better with Oct -NAO, but late Sept might be close enough

We are kind of due for a -WPO/-EPO Winter, 5 of the last 6 Winter's have been positive, and the one year that was not was Neutral. The WPO doesn't have much to do with the PDO in the Winter months Maybe more negative phases of those indexes has something to do with +NAO? I've certainly observed this Pacific-Atlantic correlation since 2013, and it actually goes all the way back to 2007.

Yeah.. we are progressing well with decadal trends this year so far.. it's actually been very similar. Now this N. American ridge, -NAO, and -PNA in late Sept/Oct is even more confirmation that we are on course with the last few years. It's hard to predict below average anywhere these days, but I think a strong -PNA for the Winter may actually take some time to build. We may see some chaos as it starts this Winter, especially early on (a lot points to RNA Feb as the decadal trend here is +120dm Aleutian ridge as the mean for Feb-Mar since 2018). I wouldn't say expect a colder than normal Dec-Jan, but watch for maybe some pattern breaks during this time..