GaWx

The following maps from Weather Desk (**Due to member limitations on attachments, on 2/10/23 I deleted the attached image that was here so I'd have room to repost it in a 2/10/23 post about the mid-Feb 2023 major SSW**) show how often the first 15 days after a SSW in the SE have been mild and how often the subsequent 15 days have been cold. (2009 is actually much colder than its 2nd map when you start the 15 day period 11 days later. 2010 was also cold immediately due to other factors/near record blocking the entire winter in that moderate El Niño). In other words, should warmth dominate in early Feb as models are suggesting, that would actually be an encouraging sign that things are going according to plan of the typical SSW pattern in the SE of warmth followed by lengthy cold. So, while seeing that warmth on the models would be (is already) leading to "winter cancel" proclamations among some, it would actually tell me the opposite. I'd then be looking with even more confidence for a new cold pattern to start around mid Feb and dominate for several weeks: * 2/10/23 edit: As stated above, I deleted the attachment to make room in my account to allow me to repost it later in this thread.

Today it is very pleasant here with highs closer to normal in the 60s and much lower dewpoints (30s). No more torchy days for awhile thank goodness!

"@We've not had a day with above normal (cold) national gas-weighted HDDs since Dec 27. The ensuing Dec 28-Jan 17 period yields the fewest GWHDDs on record since 1950 for the period (467.6 vs 30-year normal 630.0)." From Weatherdesk's Twitter -------------- So, this is pretty much saying that the E US, where HDD weighting is highest based on population/energy usage, has overall been about as warm as any Dec 28-Jan 17 since 1950 when averaged out over that 3 week period. Other than the several day long mid Jan cold snap largely associated with that very strong upper low, most days have been mild in the SE. In stark contrast and to the relief of cold lovers, the next 10 days or so look to average pretty close to normal overall in the SE with a mix of BN and AN...typical midwinter stuff. After this, indications/model consensus favor mild to return to the SE for early Feb. This is actually typical for the period near and immediately following a strong SSW. Subsequently, we'll see if the SSW helps to sharply reverse that warmth as we go further into Feb. I think it will based on prior cases of La Niña winters with major SSWs around this time of year and shortly after per the hard data in my prior post as the impending strong SSW/much warmer Arctic strat persists on the models. In my mind, it will likely be a totally new ballgame as much better players (from a cold lover's standpoint) take the field. Edit: I forgot to add that other than the GEFS, no model is forecasting the MJO to get into the warm phases outside of the COD. The bc extended Euro, in contrast, has a very inviting track back to inside the COD that then gets to the left side in mid Feb while still inside. That's pretty significant.

Followup on the 5 La Niña winters with a major SSW within late Jan to early Feb As mentioned, all 5 had multi week cold dominated periods in the SE 10+ days later within Feb/Mar due largely to a -AO/-NAO: 1971 (cold first half of Feb), 2001 (cold March), 2006 (cold Feb), 2009 (cold 2nd half of Feb to early March), and 2018 (cold March) AO on day of and immediately following the major SSW was neutral to positive before turning predominantly negative: 1) 1/18/1971: day of SSW +0.3; + to neutral for 10 days (peak of +1.5); then - on 34 of next 41 days with low of -2.8 2) 2/11/2001: day of SSW +1.5; + for 10 days (peak of +2.9!); then - on 29 of next 35 days with low of -4.9! 3) 1/21/2006: day of SSW -0.2; neutral for 3 days (peak of +0.5); then - on 13 of next 15 days with low of -2.7 4) 1/24/2009: day of SSW +1.1; + to neutral for 7 days (peak +1.9); then - on 14 of next 16 days with low of -3.2 5) 2/12/2018: day of SSW +1.7; + to neutral 12 of next 13 days (peak of +1.9); then - on next 22 days with low of -4.4! ----------------------------- Based on the above, I'm educatedly guessing the following after the SSW: - 1-2 weeks dominated by neutral to +AO with a good chance for it peaking at +1+. The La Niña favored SE ridge would likely be in control. I expect some cries of "winter cancel" over the next 1-2 weeks as this likely mild early Feb period gets closer. Don't let this initial 1-2 week mild dominated period in early Feb fool you into thinking winter is over! - 3-6 weeks dominated by -AO starting by mid Feb with lowest dipping to -2.5 or lower - In the SE, mild dominating early Feb. Cold domination starts ~mid-Feb and continues through the last half of Feb and probably into at least early March. Could extend through mid March.

Since 1958 as mentioned before, there have been 13 winters with a major SSW in the late Jan to early Feb timeframe (5 during La Niña): 1958, 1960, 1963, 1971, 1973, 1981, 1987, 2001, 2003, 2006, 2009, 2010, 2018 They tended to be cold in the SE during multi week long periods within the Feb-March period. I checked the average of three of the indices in Feb/March to see if there was a notable difference between years with and without a late Jan to early Feb major SSW: 1. AO - With SSW: -1.0; 7 were sub -0.9; only 2 of 13 were positive with highest +0.7 - Without SSW: -0.1 2. NAO - With SSW: -0.4 - Without SSW: +0.2 3. PNA - With SSW: +0.2 -Without SSW: 0.0 Conclusions: Years with a late Jan or early Feb major SSW tended to have a -AO/-NAO when averaged through Feb/Mar whereas other years averaged neutral. The PNA averaged neutral for both with and without one. Thus, it appears that the -AO/-NAO combo tendency is a major driving force in tending to make a good portion of Feb/Mar chilly in the SE soon after a major SSW. So, as we go toward Feb 10th or so and beyond, I'll be looking at the AO/NAO forecasts with extra interest.

The model consensus continues (as they have for many days now) to insist that a very strong 10 mb Arctic warming is on the way starting early next week. This will mean going from much below normal 10 mb Arctic temperatures/very strong SPV of recent days to way warmer than normal/southward displaced SPV afterward. The 12Z GEFS and other runs have been showing a 40C/72F warming at the North Pole during a mere 120 hours (0Z 1/23 to 0Z 1/28)! Some GFS runs have had 5 day warming there up to 50C/90F! In addition, GFS suite consensus suggests a peak in very early Feb that I think would be AN even for summer! What does this mean? A strong SSW late this month is pretty much a certainty. What's unknown is whether it will be called a "major" strong SSW or a "minor" strong SSW. The very impressive degree and speed of warming are there. But to be considered "major", the 10 mb winds at 60N+ have to reverse from W to E. That part is uncertain but GEFS continues to go in that direction. The 12Z GFS may actually have it. Regardless, with this strong of a SSW and it close to "major", it may not matter much. As far as the timing of effects on the SE based on past events, it appears that a multi week long cold dominated period could start as early as ~~Feb 10th and possibly last into March. Nobody knows as details are highly speculative. The potential cold shot for late next week is independent of this (SE cold doesn't normally occur at the same time as the SSW) as a mild period will most likely follow that.

It could very well be a mainly dry, cold weekend after next for most of the SE as is quite common with Arctic highs that plunge assuming the plunge occurs. However, NW flow would be favorable for another good upslope mountain event (even if not as good as the great one that just occurred) as the Arctic air comes in and this is on the models. Also, we're still 9-10 days out and there's still plenty of time for change as that's a semi-eternity in model accuracy time as you know. For a not as dry outcome, it would probably be better if the Arctic high moved through the Ohio Valley instead of a deep plunge.

If the 12Z GFS/Euro/CMC and 0Z Euro have the right idea (it is still out in semi-fantasyland), this past below normal cold weekend will have a chance to be exceeded by an even colder weekend/the second coldest Arctic plunge of the winter to date the weekend after the upcoming one! The consensus of the models has easily the 2nd coldest Arctic airmass of the winter to date coming out of S Canada and agreement is rather strong for that far out. Also, the 12Z GEFS mean is the coldest run so far for the SE that weekend. I didn't even consider a very cold last weekend of January that much of a possibility until the last couple of days and figured this past weekend would likely be the coldest one of the month.

Interestingly, if the 12Z GFS/Euro/CMC and 0Z Euro have the right idea (it is still out in semi-fantasyland), this past below normal weekend will have a chance to be exceeded by an even colder weekend/the second coldest Arctic plunge of the winter to date the weekend after the upcoming one! I'm the meantime to keep this on topic, it is now 75 with dews in the semi-muggy low 60s. What a contrast to just two days ago, when it was in the 60s with dews only in the low 20s!

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+