GaWx

Keep in mind that the MJO, though quite important, can sometimes be overruled by other factors. Whereas outside the COD phase 5 is on average one of the warmer Dec phases for the SE, that is just an average. Just last year the coldest air of the winter in the SE by far was during the period Dec 23-26, which was during high amplitude phase 5! (see below). The main driver was a very strong -AO teaming up with a moderate +PNA along with a strong -EPO that had just ended. There actually was a moderate +NAO. And it was during La Niña! At least this year we have El Niño and its favoring of a +PNA. And then we’ll see if we can get a -AO and perhaps a -NAO. So, looking ahead to Jan, if the MJO really does go into moderate phases 4-6, I wouldn’t bet the ranch on it being mild in the SE then. No recent Euro Weeklies run has had it mild.

Indeed, phase 3 on average is near normal for temperatures in NC in winter: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Temperature/DJF/combined_image.png

The first run of the Euro Weeklies that covers 1/29-2/5 has BN temperatures in the SE. This is after the prior 4 weeks all being NN to BN with BN every week over FL. Coldest two weeks are Jan 1-8 and Jan 29-Feb 5. All weeks remain normal to wetter than normal with strongest anomalies far SE and no dry areas in any week. So, El Niño climo ftw! In addition, keep in mind the increasing chance for a major SSW ~1/3-6. Starting 1-3 weeks after that there’d be a tendency per climo during El Niño for the SE to have BN temperatures dominate for a 3-8 week period per analogs. If you look at major SSW analogs, the SE US pretty much leads all areas of the US with the strongest BN anomalies. Here’s 1/29-2/5 temperatures:

Importantly, today’s Euro Weekly 10 mb wind didn’t backtrack from yesterday’s surprisingly (except to @40/70 Benchmark )weak SPV run and still has numerous members with a major SSW Jan 3-6 (more concentrated over shorter interval), which is 13-16 days out. The 2/16/23 major SSW was first strongly honed in on 13 days out for comparison. Once again, note the spike up just before the plunges. Also, I count 12 extreme (sub -15) vs 22 yesterday:

That’s especially the case the further south one goes, like down in the SE. Looking at some past cold SE winters, much of Canada was AN. If AN or even much AN Canadian air is brought down fast enough and thus not allowing for too much modification before arriving, that air can more easily be BN to even much BN the further south one goes due to warmer normals. Check out the average correlation of temperature to a +PNA in DJF for a good illustration. A +PNA is essentially a W to C Canadian block. It being warm vs normal where there’s blocking is common:

The post I was responding to mentioned how warm Dec has been for the US as a whole anomalywise. My response was to show how the degree of warmth for many who post here regularly will end up unimpressive as the warmest anomalies are elsewhere. That’s especially the case in the SE, where we’re barely AN or NN MTD now and are likely headed to an overall NN Dec. Even way down here in the deep/coastal SE I’ve already had 8 lows in the 30s or lower this month, pretty normal for Dec here. It was 27 yesterday. I didn’t say anything about snow as I was strictly addressing the Dec warmth that had been mentioned. Obviously snow for the east has been largely nonexistent to this point.

The major SSW of 2006-7 wasn’t til Feb 24th, too late to affect meteorological winter and thus wasn’t included in those that I looked at.

From this UKMET ensemble of yesterday, I count 9 of 16 (56%) members with a major SSW just for the period Jan 1-9! Between this and today’s Euro Weeklies, the signal for a major SSW in early Jan, which had already been notable for the last 3 weeks on the Euro, has gotten that much stronger.

I did a study and posted about it of all major SSWs during El Niños (excluding two in late Feb that were too late to affect met winter) and all were followed starting 1-3 weeks later by a 3-7 week long period dominated by BN temps from the MidAtlantic south while most of them had the BN domination also in the NE US.

Wow, as @griteaterjust said, this run has by far the weakest SPV/strongest concentration of members with major SSWs of any run for Jan 2-13 with the mean dipping to a mere +3 on Jan 7th vs a climo mean of +33!! The lowest of any day prior to this run was +11 to +12: It’s impossible to count but I bet there are 40+ just for 1/2-9, easily the most yet. I see ~22 that are extreme (sub -15), by a good margin the highest yet.

But from MidAtlantic south, where many of us live, it has been no more than slightly warmer than normal MTD. It has felt like a winter month to me with NN here. The SE is likely going to end up NN overall. Nothing warm about that. Also, fwiw, here's the latest CFS forecast for Jan: blue area is mainly 1-3 F BN and that's based on cooler 1984-2009 climo:

It’s new but the mean still peaks at only +30 m/s vs the climo mean up at 39 m/s. Also, ~5-6 days before both the minor warming of late Jan 2023 (way up at +50 m/s) and the major SSW of 2/16/23 (+30 m/s), there were similar or even stronger spikes. Prior to the 1/24/2009 major SSW, the winds spiked way up at 67 m/s 2 weeks prior. Similarly, prior to the 1/28/2010 borderline major SSW, the winds were way up at 60 m/s 18 days earlier as per this link: https://acp.copernicus.org/articles/12/8115/2012/acp-12-8115-2012.pdf So, wind spikes 1-2 weeks prior to SSWs may be common and perhaps normal.

Today’s Euro Weeklies are just about as active as yesterdays in early Jan with ~18 majors 1/1-9 vs ~19 yesterday. The total run has ~40 vs ~45 yesterday. I counted 9 extremes throughout vs a few more yesterday: Jan 1-8 10 mb temps/hts still looks similar:

Since it covers 150W to 160E, how much of the stronger and further west VP anomalies do you think have been caused by Nino 4 being at such strong levels for it relative to its climo? Per your map, the strongest VPs so far this month have been from 170W to 160E or right over Nino 4.

Regarding the bolded, whereas the current El Niño’s ONI is “very strong to super”, it isn’t when looking at both RONI and MEI as RONI is lower half of strong and MEI is low end moderate at best. But Nino 4 relative to its own climo had been very strong although it has cooled a good bit from its peak.

Regardless of whether or not we get an official major SSW, the Euro Weeklies have been quite consistent the last 3 weeks or so for the first week of Jan with a way warmer than normal Arctic and significantly displaced SPV at 10 mb. That’s impressively consistent and persistent implying quite a strong signal with no can kicking whatsoever! Run from 12/3/23 for 1/1-8/23: Today’s (12/18/23) run for 1/1-8/23:

12/18 Euro Weeklies: again not underneath the red line but still almost as active with ~20% majors 12/31-1/9 (vs 24% yesterday) with 19% of them 1/4-9. I count 9% extreme (sub -15) through the full run vs 15% yesterday. Full run rough estimate: 45% vs ~55% yesterday.

New Euro Weeklies remain BN to NN temps SE US through 1/29 with FL/deep SE BN just about every week. Precip: wettest anomalies deep SE/FL with AN to NN most everywhere else and no dry areas. So, typical El Niño climo ftw.

I’m no expert either. I just know that +GLAAM partially correlates to El Niño/+PNA and -GLAAM partially correlates to La Niña/-PNA/SE ridge. So, as someone in the SE US who prefers the best shot at BN temps and who thus doesn’t like a -PNA/SE ridge, I prefer +GLAAM to -GLAAM in general. El Niño climo ftw. But maybe a moderate +GLAAM vs very strong is generally best for all I know. What you said makes sense. A bit less El Niño influence? But the GLAAM drop appears temporary. And this is just the unreliable CFS. So, who knows if the dip will even occur? Who knows if the dip occurs but isn’t so temporary? CFS ensemble not trustworthy, especially over 2 weeks out!

Latest CFS GLAAM forecast: Compare that to this one from four days earlier: one can see that early Jan has fallen from 1+ to slightly negative

Today’s WCS OISST update has 3.4 at +2.03, down from +2.08 yesterday. In order to get an unrounded ONI of +2.00+, I had earlier been figuring that the daily would probably need to peak close to +2.40. However, recently ERSST has actually been as much as 0.10 warmer than OISST. So, that when combined with there having been such a long period hovering near +2.00 tells me that the daily OISST peak may not need to be higher than ~+2.20. If the Dec ERSST were to again come in warmer than OISST, it could very well end up in the +2.05 to +2.10 range. Combined with the +2.02 of Nov, that would put ND at +2.03 to +2.06. That would mean Jan could be as low as +1.90 and NDJ still end up +2.00+.

It now looks like ~Jan 3-6 is becoming the most likely period for any potential major SSW. That would still be 16-19 days out and would be right in the heart of the most favorable QBO east climo portion of winter for one. Thus I’d give it til by this weekend for the models to get more on top of this should it be real. Thus, the trend of the rest of this week’s runs will be quite telling whether it be yes or no. If real, I’d expect to see more op GFS runs from time to time similar to the 18Z from yesterday that was posted as they lead the way in Feb. This 6Z 12/18 GEFS 384 looks pretty interesting and more favorable than the comparable map from the 0Z GEFS 12/17 extended released last night:

Thanks for posting this. In advance of the 2/16/23 major SSW, the GFS op on a number of runs lead the way ahead of ensemble means in suggesting that one was quite possibly on the way. As far back as 1/31/23, when hardly any of 60 ensemble members showed one, the GFS had this (see orange line): note that there were only 2 (3%) ensemble members weaker: On 2/2/23, only 3 (5%) ens members were weaker: Similarly, only 3 (5%) members were weaker than the 2/3/23 GFS and only 5 (8%) members were weaker than the 2/5/23 GFS. By the way, the 0Z 12/17 GEFS extended had a mere 2 (6%) with a major SSW, by far the lowest in many runs! However, the 0Z 12/18 GEFS at 384 suggests that it will likely have more major SSWs than 12/17 when the extended comes out tomorrow evening.

If any of the McClellanville reports are official, they’d almost have to be alltime SC Dec records by a big margin. That’s insane! The Savannah area ended up with 3.5-5”, easily the biggest 24 hour rain in a very long time! And it lasted a full 24. I wonder when we last got that much in Dec. This storm will not be soon forgotten!

Though no longer below the red line, don’t fret because today’s update holds onto yesterday’s re-weakening of the SPV. I see ~24% majors 12/31-1/9. That is still 14-23 days out. Keep in mind as per my prior post that 15 days before the 2/16/23 wind reversal only 13% of ens members had a major. They started catching on much better 13 days before it. Thirteen days before 12/31-1/9 isn’t til 12/18-27. So, there’s still plenty of time for the ensembles to more emphatically show it, especially if it were to occur later in the 12/31-1/9 period and especially considering that that entire period is the most prime QBO east major SSW climo. The start of the active period has now gotten to just two weeks out. But I would now like to see the majors start to move to less than two weeks out over the next few days. The ens mean still gets down to +12 Jan 1-2, which is a mere 1/3 of climo and which is out 15-16 days. This is near where the mean of the ensembles was 15-16 days before the 2/16/23 major. I now count ~55 majors throughout the run vs ~50 yesterday and ~33 two days ago. I count 15 extreme (sub -15) vs 13% yesterday and 7-8% the prior two days: