GaWx

Yeah, even the ensemble means aren’t anywhere close to reliable that far out but then again the EPS has done a far better job predicting the SPV than what’s underneath. That’s why it has my interest. Also, there actually haven’t been any wobbles as big as today’s since I started looking at it closely. Is it just a wobble? Stay tuned!

Absolutely it will wobble. But it had a large wobble today, which doesn’t have the SPV fall back below normal til ~12/10. Two days ago it did that already on 11/30. I like to follow the trends/wobbles. Sometimes the wobbles are actually pointing to a new trend. But maybe it will do a hard wobble back the other way tomorrow for all we know.

Today’s EPS 10mb 60N mean wind forecast backed off a good bit more from the weak SPV having been forecasted in recent days. Two to three days ago it had it dip (vs the 35 m/s normal) to 21 m/s. Yesterday that rose to 25 m/s. Today it is up to 30 m/s along with only ~7% of members suggesting a major SSW in early to mid Dec vs 10% yesterday and 18% 2-3 days ago. Also, the Nov and early Dec. SPV is significantly stronger than yesterday:

1. Despite the WCS PDO for Oct coming in at up at ~-1.0 from Sep’s ~-2.0 and thus my expectation that NOAA’s Oct would come in within or near -1.5 to -1.8, it actually came in still down at -2.36. That’s still a decent rise from the -2.97 of Sep but is disappointing: https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/index/ersst.v5.pdo.dat 2. The WCS daily PDO rose slightly for the 2nd straight day and was at -0.99. So, NOAA daily is probably still down near or below -2. So, there’s still a long ways to go to get anywhere close to neutral. Keep in mind that last winter had a -1.70 NOAA PDO and Oct of 2022 was -1.80 vs the -2.36 of 10/2023. So, getting a NOAA PDO for DJF to average >-1.0 will not be easy!

My point is that the seasonal models, including CANSIPS, can very easily end up way off (too warm, cold, dry, wet, etc) for winter even the day before winter starts and we’re still a month out. Regarding the PDO, it was already way down at -2.41 in Nov of 22 and it actually rose during the winter (winter averaged -1.70).

“FWIW” is the key. I’ve found these long range/climate model predictions to be of little value. I’ve seen this and other ones totally blow their winter forecasts even on Nov 30th! Here’s a great example from the 11/30/22 CANSIPS for last DJF that shows the MidAtlantic states near normal (+0.25 to +0.5C or ~+0.5 to +1F) vs 1981-2010 normals. The 1981-2010 NYC normal DJF is 35.5F. This CANSIPS was forecasting NYC to be ~36.2F. The actual winter averaged way up at 41F! So, this model’s Nov 30th run was a whopping 4.8F too cold for last winter there and similarly much too cold all around there/too cold throughout the E US. Also, it was much too warm in the W US. So, it totally blew most of the country and this was released the day before winter started: CANSIPS 11/30/22 forecast for last DJF (1981-2010 normals) Actual (1981-2010 normals): much warmer E US and much colder W US vs Nov 30th CANSIPS forecast

The WCS PDO for Nov 1st of -1.02 was actually slightly warmer than that for Oct 31st. This means that the corrective fall from the huge earlier rise may be over.

Today’s EPS backed off some (though nowhere near completely) vs yesterday’s run, which had shown the strongest indications for a weakened SPV in Dec yet. Yesterday’s had the 60N 10 mb wind dip way down to 21 m/s vs the normal of 35. Today’s has the EPS mean dip to 25 m/s, which is still significant. The prior two days of runs implied ~18% of members with actual or impending major SSWs in early to mid Dec. Today’s backed off to ~10%, which is similar to the run from three days ago. At day 45, yesterday’s had ~85% of members with a SPV weaker than climo. Today’s is ~75%.

Crestview, a perennial cold spot in N FL, had a low of 27, which ties with 1993 the coldest low for the date on record and misses just by one day for coldest so early in the season as 1993 also had a 27 on Nov 1st.

That’s why I take modeled seasonal forecasts with a grain of salt. However, the Euro Weeklies have (based on many years of data) been forecasting the stratosphere through week 6 much more accurately than the troposphere as I posted about earlier. Thus, I tend to pay extra attention to strat forecasts of the extended Euro Weeklies. The persistent forecast for a weak SPV on the Euro in Dec is quite notable as a whopping 85% of the members have a weaker than normal SPV in mid Dec.

Agreed. And I think that may be even more the case if there ends up being an actual SSW, especially major, because they sometimes occur when it is mild in the E US. As it appears you’re implying, major SSWs that end up getting well down into the troposphere often lead to cold that takes 10-14+ days following one to start having a big impact. So, if there is a major SSW in mid Dec that propagates way down, any intense cold resulting from this may not even get started til after Jan 1.

@stadiumwaveaccidentally posted the Oct map as the top map instead of old Nov. Regardless, the CANSIPS old Nov map (regardless of 1981-2010 vs 1991-2020, which was a good catch) was also mainly AN and thus will likely turn out significantly too warm for Nov in the E US once all is said and done due to the cold first half. So, the idea behind the post that the CANSIPS run of last month for Nov will almost certainly end up significantly too warm at least in the E US is a good one. Also, the CANSIPS Oct forecast was too warm in the SE. Based on the persistent EPS forecasts for a weak SPV in Dec, which favors a -AO, I think there’s a pretty good chance that the current (and old) CANSIPS forecasts for a near normal Dec will also end up too warm, but we’ll see.

Today’s EPS continues with the idea of a weak SPV by mid Dec with the mean of the members’ 60N mean wind at 10 mb (well up in the strat.) dipping down to only 21 m/s on Dec 16th vs average for that date of 35 m/s. The % of members with a major or impending major SSW during early to mid Dec is similar to yesterday’s of 18%. Longterm climo based chances of a major SSW at any point in Dec is only ~10%. So, this means that the chance for a major SSW next month is per the EPS well above the normal chance even though it still isn’t likely as of now. Regardless, a weak SPV favors a -AO. Edit: ~85% of the 101 members are below the normal of 35 m/s at the end of the run, which is 12/16/23. This all means that the signal for a weak SPV is probably just about as strong as you’ll ever see at day 45 keeping in mind that ensemble means have a tendency to revert closer to climo the further out they go. In other words, it would be virtually impossible for day 45 to have 100% of members below climo. Getting 85% to do that is very hard to do unless there’s an unusually strong signal.

Indeed, 2009-10 was the last El Niño with a sub -0.25 DJF (my def of -NAO). Before that, you have to go all of the way back to the El Nino of 1986-7! And then the two prior to 1986-7 didn’t. So, only two of the last 14 El Niño winters (14%) have had a -NAO with only 1 of the last 14 El Niño (7%) winters having sub -1 (2009-10). But before that, 8 of the prior 11 El Niño winters (73%) (covering 1977-8 back to 1951-2) did have a -NAO including 3 (27%) that had sub -1 NAOs (1976-7, 1968-9, 1963-4). So, only 2 of the last 14 El Niño winters but 8 of the prior 11. Is this due largely to CC? At the same time, summer -NAOs have increased in frequency since 2007 as @bluewavehas posted about: 12 of the last 17 summers (71%) have had a sub -0.25 NAO with 8 of the last 17 summers (47%) having had a very strong sub -1 NAO! Prior to that (2006 back to 1950), only 17 of 57 (30%) had a sub -0.25 NAO summer and a mere 4 of 57 (7%) had a sub -1 NAO summer! CC? https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table

It looks to me like the winter will be a cross between an EP and CP El Niño. As we know, CP are usually the more desirable winters in the E US. And too far west can bring in too much MJO phase 6. Also, I will point out that the frigid 1976-7 was an EP and the very cold 1969-70 was a near EP. So, it isn’t anywhere close to black and white.

Looking at the three non-cold non-strong +IOD autumn El Niño winters 1994-5, 2006-7, and 2018-9, all had a +NAO and either a +AO or neutral AO vs the -AO/-NAO of 1963-4. A neutral or -NAO/-AO would probably make a big difference. Regarding -AO, today’s Euro Weeklies weaken the SPV even more in Dec than yesterday’s with an ensemble mean 60N 10 mb wind dipping way down to 23 m/s (vs 34 m/s normal for mid Dec). To show this that far out in time is quite notable. The % of members with a Dec major SSW rose from yesterdays ~10% to today’s ~18%:

Thanks. But it has still been struggling to rise big picture-wise. Same with OHC. At one point in late August, 3.4 OISST was over +1.6. Let’s see what happens now. It is a notably strong El Niño no doubt, regardless.

On that note of the +IOD El Niño autumns, 1963-4, 1994-5, 2006-7, and 2018-9 weren’t super-strong. Of those in E US: 1963-4 was a cold winter though 1994-5 and 2018/9 were mild. 2006-7 was near normal.

He should have also included 1994 and 2006 per this IOD/DMI link and even based on looking at his chart: https://psl.noaa.gov/gcos_wgsp/Timeseries/Data/dmi.had.long.data As I’ve said, I as a cold preferrer don’t like what I’ve recently learned about IOD/DMI and thus hope 2023-4 is colder than most of the winters following +IOD autumn El Niños. I have hope because there clearly are mixed signals. Plus 1963-4 was very cold. Regardless, I’ll be rooting for -IOD or neutral IOD in future El Niños.

ASO ended up at -10.45. Since 1950 prior to 2023, this is how ASO SOI came out for El Niños: - The five super-strong averaged -16 (range -11 to -21). - The four strong ones averaged -8 (range -5 to -12). - The six moderate averaged -7 with a range of -1 to -12. - The 10 weak ones also averaged -7 (with a range of +1 to -12). - Thus, this came in weaker than the super-strong range but within the upper part of the strong range for ASO. https://www.longpaddock.qld.gov.au/soi/

Latest models are pretty unimpressive. That includes the 12Z UKMET, which has no TCG.

The latest daily WCS PDO fell back some more to -0.90 (for Oct 30th). Per WCS, the PDO will come in near -1.0 for Oct vs ~-2.0 for Sep. Since NOAA has been coming in significantly more negative, that tells me that the NOAA PDO for Oct will probably come in or near the -1.5 to -1.8 range, which would be an impressive rise from the -2.94 of Sept as it would be one of the largest El Niño rises Sep to Oct. (rise likely to be in/near range of 1.14 to 1.44): Other large El Niño Sep to Oct NOAA PDO rises: -1876: 1.08 -1880: 1.79 -1918: 0.90 -1969: 2.02 -1986: 1.03 -2006: 1.08

The new EPS mean maintains after the stronger than avg Nov SPV a drop to a significantly weaker than normal SPV by mid Dec. with a mean of 25 mps (56 mph) vs climo norm of 34 mps (76 mph) for then (normals peak then). The individual members imply a 10% chance for a major SSW in mid Dec., which is significantly higher than normal as the chance for the entire month is only ~10% and is pretty high for this far out. So, that will be something to monitor. If there were to be no SSW, which is the most likely scenario, this does still imply a good chance for a -AO dominating mid to late Dec. and would put any E US mild Dec forecasts in jeopardy. Keep in mind my earlier post that shows that the extended Euro Weeklies have done much better with the easier to predict polar stratosphere than the polar troposphere because there’s little atmospheric chaos way up at strat levels:

I can’t assess personally how the Euro Weeklies have done in general because I just started following their SPV forecasts last Feb. and I only restarted following them ~two weeks ago. They did do well last Feb. Here’s the oldest one I saved (2/6/23), which forecasted the mid Feb major SSW impressively well along with the SPV remaining quite weak into March instead of recovering much: The following graph of Feb 10th forecasts during 2003-22 for 60-90N suggests that the extended portion of the Euro Weeklies likely does much better with the stratosphere vs the troposphere. Note the 60%+ performance (two darkest greens) for above 100 mb (the stratosphere) through the entire six weeks of Weeklies vs significantly worse performance in the mid to lower troposphere (250 mb and lower levels). The explanation is that the strat is easier to predict because of it being so far above the surface, where there isn’t nearly as much atmospheric chaos: Thus, the recent EPS forecasts for a weaker than avg SPV in mid Dec should probably not be dismissed as mere extreme speculation. If we are actually able to get a solid -AO in Dec, then that obviously would increase the chance that the forecasts calling for a mild E US Dec would be out to lunch. I’d be a bit nervous right now if I had a mild E US Dec. Regarding El Niño Decembers since 1950, these 8 had a -AO: 1958, 1963, 1968, 1969, 1976, 1987, 2002, and 2009. So, about 1/3 of them had a -AO (near climo % chance for all Decembers). Which of these 8 were cool to cold in the bulk of the E US? All but 1987, which was slightly AN. Explanation: its -AO was only weak (weakest of the 8) and it was the only one of the 8 without a -NAO (it was weakly +NAO).

The extended Euro ensemble has consistently for many days been forecasting a stronger than average strength SPV in Nov (peaking Nov 11th in near record high territory) followed by a weakening SPV to near neutral late in Nov. For the last week or so, it has also been forecasting the weakening to then progress to a significantly below average strength SPV by mid Dec, which implies a good shot at a -AO then along with a better than average potential in mid Dec for an SSW. But keep in mind that sudden SSWs are uncommon in Dec as peak season doesn’t even start til mid Jan. So, this could very well end up as a -AO/weaker than average SPV without an SSW, which would still be a cold signal for the E US especially if a -NAO could somehow accompany it: