GaWx

Well Tony, don't shoot the abacus lol. In the first week of Feb for whatever reason, I could find no major snow or sleet officially at Atlanta! I found nonmajor ones, of course, and several bad icestorms. And I'm sure you know there have been a good # of major snows/sleets both the week before and the week after. (Peak at Atlanta is near mid-Feb.) One of these days that will change for the first week of Feb. Maybe that's what you're alluding to for this year as that would be highly anomalous!

This area had a severe thunderstorm go through ~an hour ago. This caught me by surprise. But I didn't detect any lightning/thunder. Just heavy rain and gusty winds. Since last night, we've had very beneficial rains in the general vicinity of 1". I haven't seen my measurement yet. Edit: It was near 1" for me.

Thanks. If it occurs, I think it would be near or just after the end of the rapid 10 mb Arctic warming or, say, ~1/28 or a little later. The 60N winds will drop drastically per models from their pre SSW near 50 m/s to under 15. If they would get to below 0, that would be considered a reversal as I understand it. But what if it were to stop at, say, 10? That would be 80% of the way to 0. Would that be close enough effectwise to result in similar changes to what an actual "major" typically causes?? The N Pole is progged to warm up at 10 mb from near -75 C to ~-35 C on 1/28. Normal/average for that date is ~-55 to -60 C. But then it is progged to warm further to -20 C on 2/2, which would be 35 C AN for the date and 10 C AN for mid summer high normals! *Edited for corrections

Tomorrow will be when the SSW starts in the Arctic. This has been the timing on the GEFS since I started following it closely a week ago. It still looks about as strong as it ever has on the GEFS. The N Pole is still progged to warm at 10 mb a whopping 40C/72F+ during just a 5 day period ending 1/28! And then it warms even more into early Feb. What's still in doubt is whether it gets classified as a "major" SSW or a "minor" SSW. "Major" requires a wind shift from W to E at the 10 mb level at 60N. Regardless, it will be a strong SSW (rapid, strong warming). The eventual effects on the SE remain to be seen. However, the history of actual "major" SSW events suggests that the bulk of potential significant, persistent cooling in the SE US related to this would most likely not occur til at least 10-15 days after the SSW (per the maps I posted two days ago) when a -AO dominates. These same maps as well as stats I looked at suggest that the 1-2 week period right after the SSW would typically average near to AN prior to the cold with a +AO prevailing. Looking at the MJO forecasts, the GEFS is still largely on its own with a forecast of a moderate phase 4 within two weeks. The others turn back into the COD, which wouldn't be a warm signal. We'll see how this evolves, especially since it may not reach the "major" SSW classification. But would that matter much with this strong of a warming? We'll see.

I'd say we're already in the midst of a pattern shift from torch dominating most of the month to averaging near normal (some BN and some AN) for the rest of this month and possibly further in the SE and in much of the E US. Ironically, the 12Z EPS is significantly colder overall vs prior runs in the SE (coldest run in quite awhile) in the 11-15 day. The last couple have been colder than prior runs. Also, the 12Z GEFS is as cold as any of the last few days. Neither ensemble now has it mild in early Feb. with near to a little BN on the 12Z EPS/GEFS in most of the SE. The colder model trend could be a psyche/wrong, of course, especially with them being too cold overall this winter to date, but regardless, I didn't see a model cooling trend coming. 12Z EPS mean of 51 members is a whopping 10 F or so colder in not only the SE US but also almost the entire E 1/3 of the US vs just three runs ago in much of the 11-15! Example: the ensemble mean at Charlotte for 12Z on 2/4 was an AN 40 just three runs ago and is now a BN 30!

A once in 125 year series of deep SE winter storms that suddenly appears on a GFS run out 12-14 days gone on the next run? I'm absolutely shocked and stunned! But it is entertaining to see these fantasies. The extreme inaccuracy of models that far out allows for crazy fantasies to appear every once in a while. Based on the timing of the upcoming SSW and considering ensembles, I'm expecting this period and a bit beyond to be dominated by near to warmer than normal. The start of a cold dominated pattern related to the SSW would probably not be before ~Feb 10th at the earliest based on analogs (shown on maps I posted yesterday). Around then winter will most likely be restarting! Far from over imo!

Yeah, like 1899 that 12Z GFS fantasy winter storm was all the way down to (and past) Phil @pcbjr in Hogtown/Gainesville with ~1/4" of ZR. Unlike 1899, this fantasy is from a series of lows and a large portion of the heaviest SE US qpf is actually ZR with some sleet. The precip in N FL, and SE GA/SC/NC is nearly 100% ZR/IP with the 850 mb 0C line to the NW. It would be a massive/historic icestorm for much of that area but fortunately it isn't real. The odds actually favor near or above normal temperatures around that time based on ensembles and the typical timing of SSW effects on the SE.

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.