GaWx

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.

The 12Z EPS is the strongest yet with its +PNA with (in dm at H5) +17 peak anomaly W coast and +15 peak E US. This is much stronger than the 12Z GEFS, which itself was stronger than its own 0Z. The 12Z CMC is similarly strong to the 12Z EPS. My very rough guess as to the 12Z PNA peak on the EPS is +1.5. How strong is that? The peak on 12/26/22 was +1.3. In January, the only ones since 1950 with a daily PNA peak higher were during 2016, 2002, 1995, 1981, 1977, and 1961. So, that is fairly rare in January (~8% of them). The GEFS mean based AO forecast is for ~-1 for then. So, what if the EPS isn't exaggerating the PNA (which it sometimes does) and there is a +1.5 PNA peak combined with a -1 AO? I wonder whether or not that is a significant indicator for cold in the SE in any part of January that has that.

The 3 major ensemble means continue to show a -AO late in their runs along with at least a moderate +PNA. This combo in itself is a positive for a BN dominated period in the SE late this month. Next up: 12Z EPS.

The 0Z EPS held onto the pattern change to +PNA/much colder very nicely. This goes back 4 or so days of runs now. The west coast ridge is the strongest yet. The mean trough is west of the SE allowing for ample moisture and a potential chilly wet period late this month, especially when also considering the progged drop in the AO.

The late 12Z GEFS taken literally (yes I know this is way out in Lala land and thus has limited credibility) says don't give up on the rare chance (only 1 in 25 odds based on last ~140 years) for a 3"+ snow month at RDU during an overall mild winter month. It suggests two Canadian highs may come down late this month with a somewhat split flow bringing in Gulf moisture up against a solid +PNA between the two highs. Again, just fwiw but that's appropriate speculation imo for this thread. Yes, the Canadian source regions will be mild for awhile. But keep in mind that even with that, a solid +PNA is usually cold relative to normals in the South. So, regardless of whether or not there'd actually be a winter storm threat, a pattern change to much colder late month is looking more and more likely. Edit: 12Z EPS is still on board for the colder change/+PNA for ~1/21. The trough axis is slightly further west than the 0Z, which is a good H5 flow for a potential winter storm wet/chilly vs dry/cold).

The Dec 2022 AO ended up way down at -2.7. That's the second lowest AO on record back to 1950 with only 2009's -3.4 lower! Here is the subsequent Jan AO for the strongest Dec -AOs: Strongest Dec -AO/Jan AO 2009: -3.4/-2.6 6th strongest 2022: -2.7/??? 2010: -2.6/-1.7 top 20% 2000: -2.4/-1.0 1995: -2.1/-1.2 top 25% 2005: -2.1/-0.2 1976: -2.1/-3.8 strongest 1985: -1.9/-0.6 1950: -1.9/-0.1 1969: -1.9/-2.4 9th strongest 1952: -1.8/-1.0 The above tells me that there's a good shot at a sub -1 this month though that would probably require a sub -1 for the last week of this month. Implications for February? Not much per these analogs. Whereas a -AO could be argued to be slightly favored over neutral or +, Feb of 2011 went strongly + with a +1.6!

The 0Z EPS is still consistent with its prior runs as regards the developing +PNA late in the run. It actually looks a touch colder thanks to a few more members with pretty strong Arctic highs. Baby steps. Let's see if it remains over the next few runs. If it does and looks like a real deal, the next question will be about its longevity prospects.

Since 1950 at KATL, there have been five La Niña Febs at one BN or colder out of 21 (2009, 2006, 1996, 1985, and 1971). I decided to check out the PNA, AO, NAO, and EPO for these five to see if there were any tendencies: PNA: -1.0, -0.1, -0.3, -0.5, +0.1; AVG -0.4 AO: -0.7, -0.2, +0.2, -1.4, -0.9; AVG -0.6 NAO: +0.1, -0.5, -0.1, -0.5, +0.2; AVG -0.2 EPO: -24, -34, -20, +75, +85; AVG +16 The coldest Feb (2006) had a PNA of -0.1, an AO of -0.2, an NAO of -0.5, and an EPO of -34. Surprisingly, there was no +PNA tendency for the colder five. The most significant tendency was a -AO. Now I'll compare these averages of the indices for the five colder Febs with that for the warmer 16 Febs: PNA: +0.7, -0.3, -1.0, +0.8, -1.6, +0.5, -0.2, +1.1, -0.1, -1.1, -1.5, -0.2, -0.9, -1.0, -1.7, -1.0 AVG PNA for warmer: -0.5 AO: +1.6, -1.2, +0.1, -0.0, +1.6, +0.9, -0.6, +1.1, +0.5, +3.3, +1.7, +0.2, -0.5, -2.0, -1.5, +0.6 AVG AO for warmer: +0.4 NAO: +1.7, +0.1, +1.6, +0.4, +0.7, +0.7, +0.5, +1.7, +0.3, +2.0, +0.9, -0.6, -0.1, -1.1, -1.1, +0.4 AVG NAO for warmer: +0.5 EPO: -16, +50, -70, +48, -16, +86, -41, +34, +194, -232, +89, +44, +135, +51, +6, +101 AVG EPO for warmer: +29 --------------- The warmest Feb (2018) had a PNA of -1.0, AO of +0.1, NAO of +1.6, and EPO of -70. The average PNA was ~same for warmer vs colder. The average AO was significantly higher at +0.4 vs -0.6 while the average NAO was also significantly higher at +0.5 vs -0.2. The average EPO was just a little bit higher at +29 vs +16. Conclusion: The biggest drivers to determine warmth vs chill for La Niña Febs appear to be AO and NAO. If we could get a sub -1 AO, a sub -0.5 NAO, a PNA of no lower than -0.5, and an EPO no higher than +100, I'd feel there'd be a decent shot at a Feb at one BN or colder.

I prefer BN/lower than average dewpoints for all months of the year. Just add Feb in and this forecast would be perfect for me! The 12Z EPS progressed well vs the last 4 runs. So far so good for cold lovers! Let's see if an actual pattern change in January can hold on the EPS for a change. The prior two attempts (1/9-10 and midmonth) have apparently since failed with the overall mild pattern still not breaking on the models til at least 1/21 or so. The end of the 12Z run shows a solid +PNA with 10-12 dm AN H5 heights Pacific NW and 8-10 dm BN centered over the lower Midwest. BN at the ground is coming into the SE near the end. It still doesn't look very cold yet as there still aren't more than a few members with big Arctic highs coming down, but it is a start and would mean much colder than the preceding warmth if it were to verify.

Today's GEFS based forecast for day 14 has slight improvements vs yesterday's forecast from the perspective of someone who prefers that a colder pattern return in late January: - gets back to a weak +PNA after a -PNA that starts ~1/15 - AO rises to neutral but then falls back to moderately negative; very strong Dec -AO favors sub -1 AO in January. To have a good shot at that, a mainly sub -1 will likely be needed for 1/22-31 - The current moderate to strong +NAO falls back toward neutral Regardless of whether or not a BN dominated period returns at some point during the last 10 days of the month, January will almost certainly end up quite a mild month for the SE as a whole and much of the E US. It has a good shot at being one of the warmest nationwide since 1950 from a population weighted heating degree perspective. So, a near normal Dec and a mild January in the SE US. What will February bring? That's the big question. Any educated guesses?