GaWx

Models are as emphatic as ever about very strong stratospheric warming/SSW late this month into early Feb. Many Arctic areas are projected at 10 mb to warm 40-50+ C (72-90+ F) within just 5-10 days! The trend at 10 mb has been slowly toward a further N Alaskan ridge and further S SPV. These trends are increasing the chance that any SSW will be "major", which means that the mean wind direction north of 60N shifts from W to E. The chance for a major SSW is higher during the 2nd half of winter. Since 1958, there have been 13 winters with one in the late Jan to early Feb timeframe or 20% of them: 1958, 1960, 1963, 1971, 1973, 1981, 1987, 2001, 2003, 2006, 2009, 2010, 2018 How many of these 13 had significant multi week long cold periods to follow starting 10+ days afterward in the SE? Using ATL: 1958, 1960, 1963, 1971 (La Niña with cold first half of Feb), 1973, 1987, 2001 (La Niña with cold March), 2006 (La Niña with cold Feb), 2009 (La Niña with cold 2nd half of Feb to early March), 2010, 2018 (La Niña with cold March) - So, 11 of the 13 had significant cold to follow in Feb and/or March - So, specifically looking at just the 5 La Niña winters with a late Jan or early Feb major SSW, all 5 later had significant and lengthy cold to follow in Feb and/or March. Conclusion: Because of the very strong SSW progged late this month, there's a very good chance for a multi week period in the SE dominated by significant cold in Feb and/or March starting at some point 10+ days after the SSW, which means most likely 2/10 or later.

1. The 12Z EPS through 240 maintained the warmer trends of the last few days after having been a few degrees BN on several runs last week for the same days and is still mainly AN in the 6-10. That has how the EPS has been several times this month making it hard to trust it when it is significantly colder than the GEFS. 2. The 12Z EPS, similar to its 0Z, has cooled significantly from AN to several degrees BN in the 11-15. Whereas I'd love that to be real and thus hope it is for a change, I know better than to trust this. See #1 just above this for a key reason not to. It has been too cold (especially) in the 11-15 many times this winter to date and thus has tended to warm up as it gets closer (like a cold mirage). Another reason is that the GEFS, which has done better because it has been warmer much of the time this month, is warmer here too at near normal though it has cooled some. 3. There looks to be very cold air not too far NW of the SE US and also a southeast ridge lurking close by to the SE. So, there is higher than normal bust potential to go either way. There could easily be a sharp gradient within the SE. 4. None of the above points have anything to do with the progged SSW for next week. Any possible cooling effects from that on the SE US would likely not be til Feb 10th+.

but it should just say "we're closed just temporarily" because: - something interesting for especially parts of NC/VA next week can't yet be ruled out, which is normally the case when looking over a week out during the heart of winter with progged very cold air not too far away - The North Pole is progged on the 12Z GEFS to warm in the stratosphere at 10 mb a whopping ~45 C/81 F within the 5 day period from 1/23 to 1/28, which would be due to a SSW (though maybe not technically a "major" one). With this kind of warming, a change to a multi-week cold dominated pattern is quite possible in the E US starting maybe as early as ~Feb 10th (call it mid-Feb), especially if the MJO is not then outside the COD in phases 4-5 and the +NAO ends. - This is despite the infrequency in having a cold Feb during La Niña. Infrequency doesn't mean it can't get cold. Also, only 18 of the last 34 (53%) La Niña Febs have actually been 2+ warmer than normal (what I consider AN) at KATL. So, that is barely more than a coin flip. The number of torches (5+ AN) is only 9 of those 34 (26%). So, the idea of a mild Feb during La Niña, while higher than the typical chance, is nowhere near a guarantee. Near normal occurred 11 times (32%) and BN 5 times (15%). With this progged late January strong SSW, I'd put the odds of an AN Feb at well under the typical 53% chance and increase the chance of normal or BN to higher than the typical 47%.

I wouldn't call it a "major" SSW (at least as of yet since that requires an actual reversal of wind direction from W to E at 60N+), but a very strong warming is forecasted by the 6Z GEFS (and earlier runs) at 10 mb. These maps show a whopping 40C (72F) warming in some Arctic areas at 10 mb over just a 5 day period 1/22 to 1/27 along with a significant weakening and some southward displacement of the currently very strong SPV. If that ridge in the 2nd pic below over Alaska were to instead be N of Alaska along with the SPV being further south and even weaker, then I think this could possibly be called a "major SSW" since winds would reverse from W to E in some of the areas near and north of 60N. This would be possible considering model trends over the last few days. Any possible significant cooling effects on the SE US wouldn't be til mid February say, second week or later. Though La Niña climo makes it difficult for Feb as a whole to be a cold month in the SE, a good number have been near normal. Feb could start warm but end quite cold (meaning a near normal Feb overall) if this were to play out just right based on this strat. timing. By then, the MJO would possibly also be moving out of the typically warm MC region. Any calls for winter to be over soon in the SE even if we end up mild late Jan into early Feb would be quite bold considering this.

What a contrast to KSAV, which has had only 5.85" since way back on September 12th vs a normal of 12.54"! This comes out to only 47% of normal over the last 4 months. But this is fairly typical of La Niña, which favors the driest in the SE closer to the SE coast thanks to the prevailing southeast ridge mainly November through March. Here's the latest SE Drought Monitor map, which comes from here: https://droughtmonitor.unl.edu/data/png/20230110/20230110_southeast_none.png

I'm very much enjoying this well below normal cold weekend while I can get it as there's no telling when the next one will occur. It is now 38 with a light freeze expected later.

I'd like some good rains if we can get them as we're in a typical La Niña generated drought. I'd take 2.3" during just this 10 day period in a heartbeat. But I don't have that much confidence in the Euro or any model out much past 5 days, especially as regards storm tracks/qpf.

It would be hard to call your bet a loser as of the latest anyway. As mentioned, the 12Z EPS was a few degrees warmer than yesterday's 0Z EPS warming it from slightly BN to slightly AN, but still significantly colder than the torchy 12Z GEFS. But the new 0Z EPS is warmer than the 12Z EPS and is now mainly AN in the extended and as warm as the 0Z GEFS. It literally has no pattern change for the SE.

Indeed, the 12Z EPS is still significantly colder than the blowtorch 12Z GEFS even with it being warmer than the 0Z EPS overall through ~hour 312. I also agree that the 12Z EPS is significantly closer to the 0Z EPS than to the 12Z GEFS. However, I think @NorthHillsWxis right in implying that the EPS has more often been too cold than too warm. So, future EPS runs not going back to the colder 0Z EPS wouldn't surprise me though I hope that's not the case. On a number of occasions this month, the EPS has backed off of a sustained pattern change to colder.

You win your bet. The 12Z EPS is significantly warmer in days 7-13 vs the 0Z. It now is a little AN averages out vs a little BN on the 0Z.

12Z GFS/GEFS are still a torch. 12Z CMC is much warmer than 0Z late in its run fwiw. Will the much colder than GFS suite 0Z Euro/EPS/GEPS start to give in to warmer at 12Z or will they hold their own? Any guesses?

Hot off the press, the 0Z EPS is a bit colder than the last two runs for most of the 11-15 with ground temperatures a few degrees BN. The EPS is much colder than the torchy GEFS in the 11-15. Model wars!

0Z Euro/CMC is a good bit colder than the torchy 0Z GFS in the SE in the 7-10 day, especially up at 850 mb. Also, the 0Z UKMET at day 7 is more similar to the Euro/CMC than the GFS. The 0Z Euro changed quite a bit late in the run. But that's the nature of operational volatility especially after day 7. So, lots of uncertainty coming towards next weekend. A little tweaking of the Euro and it could get interesting.

Pretty good rains with embedded thunderstorms since ~10 PM and it is still falling with it possibly lasting til 2AM. I'll get my total later. Edit: ~0.5". The rain is beneficial due to the new Niña related drought conditions here. It has been dry overall for four months.

Actually, it is the novelty of wintry precipitation in the SE that makes it more exciting and magical when it finally occurs. I average less than just about every very active SE poster (a mere one in four winters and with many of those just minor or trace events) and yet that doesn't reduce my interest in following wx in winter, my favorite season to read and post about. In every winter, I have the hope that there will be the rare wintry event. And if I don't get any that winter, I don't feel I've wasted time because it was interesting to follow and discuss, regardless, because it is a fun hobby. I'll add that there's a lot more than wintry wx IMBY that gets me interested in discussions even though it is most interesting when it is here, of course. I also enjoy following other aspects of winter. Examples: - temperature, especially cold which I get here repeatedly every year - indices, which I love to follow and compare to historical stats - wintry wx prospects and history in other areas, like RDU and ATL - Due to the high variability alone, it is much more interesting than following the dog days of summer. Although it is hard to beat posting about wintry wx prospects IMBY like it is for many posters, most of my posts have nothing directly to do with wintry wx prospects here. If they did, I'd be hardly ever posting.

Followup: Today's GEFS remains insistent on the -AO streak going at least another 14 days. That would then put it at 65 days and counting if it were to verify, the third longest on record and the longest since 1960! Longest -AO streaks back to 1950: 12/25/1959-4/4/1960: 102 days 2/2-4/11/1958: 69 days 2/5-4/9/2013: 64 days 12/23/1962-2/23/1963: 63 days ------------------- Current 11/23/2022-1/12/2023+: 51 days+

RDU received significant snowfall the last two late January's (2.7", 1.6"). Based on the ensembles as they look now, it appears that they'll have a halfway decent shot for a third wintry late January in a row. Anyone want to make a prediction on whether or not they'll get 1"+ of SN/IP and/or 0.10"+ of ZR between January 21st and 31st? This impending pattern change for late January looks fun to me and that's even with me having very little chance for wintry precip due to poor climo for that this far south. I just enjoy cold patterns. Many times in late January we don't have this kind of change to look forward to. So, I feel fortunate. In the meantime, the last week or so of wx here has been quite enjoyable for walking. I'm also looking forward to the upcoming cold weekend with highs of only 50-55 and lows of 30-35. The weekend looks to average ~8 BN with very low dewpoints. Great for outdoors!

The 12Z EPS suggests during the +PNA for the first Canadian high to come down 1/21-2 to start the cooling pattern change. Then a stronger, colder high comes down ~1/24 followed quite possibly by a third one ~1/26. It is between the 1/24 and 1/26 highs that I'd look for perhaps the best shot at wintry mischief in parts of the SE as by then it could easily be cold enough if any surface low takes a favorable track for one's area. Per climo the chance would be best imo if any cold enough Canadian high center moves to the Ohio River area and then eastward, which would still allow for cold enough in the SE, possibly including CAD, but also enough Gulf moisture. (See Alan's maps). This is as opposed to a high center plunging into the Deep South, which would normally be colder but a mainly dry outcome outside of NW flow in the mountains. Edit for entertainment only: it appears that one member drops a good bit of snow over N GA to NC 1/23-4.

So far (through 288), the 12Z EPS has gone back stronger to the strength of yesterday's 12Z western ridge, but it is centered a bit further west/just offshore the west coast vs at the west coast 24 hours ago. It is centered ~200-300 miles west of where it was on yesterday's 12Z as of 288. But it still shows a clearcut pattern change to much colder vs earlier days in much of the US, including the SE. In the SE, it is colder than the 0Z and at least about as cold as yesterday's 12Z.

Longest -AO streaks back to 1950: 12/25/1959-4/4/1960: 102 days 2/2-4/11/1958: 69 days 2/5-4/9/2013: 64 days 12/23/1962-2/23/1963: 63 days ------------------- Current 11/23/2022-1/11/2023+: 50 days+ 0Z 1/11/23 GEFS 14 day fcast is even more emphatic about keeping the streak throughout, which would make 64+ days if verified, would mean at least a tie for third longest, and would then be only 5 days from tieing second place. At RDU, the current 50 day -AO streak has averaged ~2 AN. We'll see where this ends up whenever the streak finally ends. If it were to end up AN or even NN, it would be notably mild vs the other four -AO streaks that were noted: 12/25/1959-4/4/1960: 5 BN 2/2-4/11/1958: 6 BN 2/5-4/9/2013: 4 BN 12/23/1962-2/23/1963: 6 BN vs 11/23/2022-1/11/2023: 2 AN but streak ongoing

We continue to have pretty close to normal midwinter temperatures here with highs in the 60s and lows near 40. Nothing torchy about the last 6 days or so. And all with near perfect dewpoints often in the high 30s to low 40s. The one bad thing is that rainfall here since ~Sept 11th has been well BN with drought returning though we did get 1" a few days ago. This dryness is typical of La Niña here. To review, we had extreme La Niña dryness mid Nov 2021 through May of 2022. Then it was very wet July 2022 through early Sept. with water table way up then. La Niña dryness is typically not a factor April- Oct. Now back to very dry.

No operational model, even the best, has all that much credibility for details past about day 7 imho. There's too much uncertainty after then. I, like many of you, enjoy looking at them and sometimes even post about them for the record or entertainment (like for winter storms)(though I may post about them in banter if way out in lala land). But I feel that about all they're semi-reliable for past day 7 is general pattern ideas. Example: the big cold of late December. After day 7, I usually concentrate more on ensemble runs, especially the means. Even during days 5-7 the best operationals can be off quite a bit, especially when there's a complex pattern. Regarding the ensembles, even the EPS has had a number of false runs regarding a general pattern change to colder this month as several of us have stated. The EPS, despite being the best, is quite fallible. That's why I often compare it and other ensemble means to prior runs as that may give me an early hint of bigger changes in future runs. I will say that after many runs showing a stronger and stronger PNA, the 0Z EPS actually backed off some on the +PNA intensity vs 12Z yesterday, despite still being stronger than the GEFS. Let's see what it shows at 12Z.

Great stuff! Per NOAA: 1. That 3/11/1960 storm gave Charleston accumulating snow and it nearly did that even down here! It was barely too warm and was just a very cold rain here per the records. 2. ATL had not one or two but THREE major winter storms in the first 11 days of Mar of 1960!!! (one ~4" snow and 2 mainly ZR/IP). That's insane! 3. Many areas of the SE had March temperatures that were BN for January! Get a load of this: March of 1960 was colder than any month of that as well as the prior met. winter!

Thank you for that info. That's quite a contrast for wintry precip! I just checked to add to your info by using RDU: 1960: March coldest by far on record; Jan N; Feb: B; Feb-Mar 18.7" SN/IP plus a good bit of ZR it appears! 2013: hardly any wintry precip; Feb N; March MB: 7th coldest, coldest since 1965 1958: 6th coldest Feb with 3.9" SN/IP; Mar tied for 5th coldest (T of snow) but that was El Niño 1962-3: 4th coldest DJF (behind 3 weak El Niño winters); major ZR 12/25, 7" snow in Feb So, regarding temps, all four long -AO periods were cold to very cold overall even though wintry precip varied a lot.

Since November 23rd, there has been a -AO every day, which is 49 days straight. Today's GEFS 14 day forecast mean keeps the -AO steak going to the end, which would be 63 days in a row should it verify. Since 1950, longest -AO streaks: 1. 102 days: 12/25/1959-4/4/1960 2. 69 days: 2/2-4/11/1958 3. 64 days: 2/5-4/9/2013 4. 63 days: 12/23/1962-2/23/1963 So, if the GEFS mean were to verify, the current -AO streak would tie for 4th longest and be just one day from tieing for third. It would be 6 days from tieing for 2nd.