GaWx

More on how cold next weekend's airmass might be in the NE, which would be relevant to how cold the SE may get via wedging: For the record (not because I believe it though it will be interesting to follow), the 12Z Euro has -2 at LaGuardia at 168! That would be the coldest there since the -3 of 1/19/1994. But that's very likely going to verify too cold being that it is an extreme operational run at day 7 and there has been a cold bias with models overall. To show how extreme this run was, it had +10 there on the 0Z and low 20s on yesterday's 12Z. To compare for the 12Z runs, the UKMET has +6, GFS +18, CMC +19, and ICON +23. The 18Z GFS is much colder than its prior run and has +6. This extreme Euro run has -40C at 850 mb then in N ME, which would not be far from the coldest on record in the lower 48/just above the coldest in the Midwest for the 1/1985 extreme outbreak. The CMC also has -40C while the UKMET has -39C and the JMA has -37C. The 12Z GFS has it down "only" to ~-31C. Regardless of the likelihood that the 12Z Euro is overplaying the degree of cold at the surface, there may very well end up being the coldest air in a good number of years in the NE a week from now.

For the record (not because I believe it though it will be interesting to follow), the 12Z Euro has -2 at LaGuardia at 168! That would be the coldest there since the -3 of 1/19/1994. But that's very likely going to verify too cold being that it is an extreme operational run at day 7 and there has been a cold bias with models overall. To show how extreme this run was, it had +10 there on the 0Z and low 20s on yesterday's 12Z. To compare for the 12Z runs, the UKMET has +6, GFS +18, CMC +19, and ICON +23. The 18Z GFS is much colder than its prior run and has +6. This extreme Euro run has -40C at 850 mb then in N ME, which would not be far from the coldest on record in the lower 48/just above the coldest in the Midwest for the 1/1985 extreme outbreak. The CMC also has -40C while the UKMET has -39C and the JMA has -37C. The 12Z GFS has it down "only" to ~-31C. Regardless of the likelihood that the 12Z Euro is overplaying the degree of cold at the surface, there may very well end up being the coldest air in a good number of years in the NE a week from now.

The coldest of the winter to date by a good margin is going to be close to, if not in, the NE possibly down to NYC a week from now (2/4) per the 12Z consensus. Something to watch to see how strong of a wedge, if any, would then get the low level cold into the SE. The 12Z Euro is the coldest run yet next weekend in much of the SE with hard freezes at least down into NC. The GFS combines this strong NE cold with moisture to yield wintry precip in the main Carolina CAD region. The PNA has trended toward a decent + for next weekend. Edit: the 12Z Euro has the coldest in Boston and Hartford since at least 2016!

The 12Z Euro's H5 SE ridge, when centered over the FL Strts late Wednesday morning is up at a whopping ~593 dm, the strongest yet for it on any of its runs.

I promise you that you'll survive. I've seen snow only once (for ~two hours) in over 7 years and was frankly lucky to see that. I'm alive and well! What doesn't kill you makes you stronger. I still enjoy winter a lot more than any other season because of the larger variability as well as higher % of lower dewpoint days making it more ideal for me for outdoors. And I can always dream of seeing another miracle snow whether it be this winter or some winter down the road. Meanwhile, I'm still hoping for another cold period later in Feb. As a matter of fact, La Niña/cold ENSO is (perhaps surprisingly) more conducive in Feb/March to an extreme cold shot into the SE than warm ENSO despite being warmer overall than El Nino per recent research I did going back to 1800s. I may share this later. A bit counterintuitive imo.

The 18Z GFS has almost pure snow for much of NC and has the heaviest snow there in many runs!

Absolutely, desperate times, indeed! But at least I'm not throwing the NAVGEM or CFS. And the big difference starts before day 7. At 168, the lowly regarded JMA has the 850 0C line 300-400 miles S of the others. Also, where the others have the 0C line then, the JMA has -10 to -15 C.

Starting at 144, one can see how different the 12Z JMA is vs all of the other 12Z runs with the southern lobe of the TPV further south resulting in colder air moving much further south into the S Plains. At 168 you can see how much colder it is in the SE with troughing to the Gulf coast along with an Arctic high bringing much colder air in vs the SE ridge hanging on all of the others. This is deep cold as opposed to shallow cold from CAD. I'm assuming the outlier JMA is going to end up wrong based on it largely being an inferior model, but thought it was worth documenting this in case it were to score an upset win.

The 0Z GFS/GEFS are mainly warmer in early Feb than prior runs as the SE ridge dominates.

The 0Z Euro is the opposite of the prior run as noted above and instead the freezer door is open late deep down into the SE! But as always, take with a huge grain that far out and we'll see what the next few runs show as well as the EPS.

Don, I thought you might find this interesting. I posted it in the SE forum: Longest -AO streaks back to 1950 along with RDU temperature anomaly 12/25/1959-4/4/1960: 102 days/ 5 BN 2/2-4/11/1958: 69 days/ 6 BN 2/5-4/9/2013: 64 days/ 4 BN 12/23/1962-2/23/1963: 63 days/ 6 BN 11/23/2022-1/23/2023: 62 days/ 3 AN The recent -AO streak apparently ended yesterday at 62 days. What's very notable is how much warmer it has been in the SE US vs during other very long -AO streaks with an anomaly of +3 at RDU vs the other four having had anomalies of a very cold -4 to -6! And on top of that, I'm using updated 30 year normals in the calculations, meaning a warmer normal for the current streak.

Well, the good (from a cold lover's standpoint) and not so surprising news is that the 12Z EPS mean says that the operational is drunk with its SE warmth late in the 6-10. Also, other than a little bit of can kicking, EPS retained its chill of prior runs and actually is slightly colder than prior runs in much of the 11-15.

If you were hoping for a Euro run with implications for cold to dominate the SE in early Feb, the just out 12Z isn't the run for you as the SE ridge holds the cold back. Prior runs looked better, especially yesterday's 12Z. And this isn't a surprise based on the frequent overzealousness of models bringing cold to the SE this winter. But then again, there's the usual high uncertainties with operational runs out past a week or so. So, take with a grain as it is still early.

Longest -AO streaks back to 1950 along with RDU temperature anomaly 12/25/1959-4/4/1960: 102 days/ 5 BN 2/2-4/11/1958: 69 days/ 6 BN 2/5-4/9/2013: 64 days/ 4 BN 12/23/1962-2/23/1963: 63 days/ 6 BN 11/23/2022-1/23/2023: 62 days/ 3 AN The recent -AO streak apparently ended yesterday at 62 days. What's very notable is how much warmer it has been in the SE US vs during other very long -AO streaks with an anomaly of +3 at RDU vs the other four having had anomalies of a very cold -4 to -6! And on top of that, I'm using updated 30 year normals in the calculations, meaning a warmer normal for the current streak.

12Z Euro is delayed due to maintenance being done:

Note that the GEFS forecast is for a +NAO in early Feb. Since 1950, 6"+ snowstorms at RDU have occurred equally frequently between +NAO (~1/3), neutral NAO (~1/3), and -NAO (~1/3) as I've posted in the past, which admittedly was a surprise to me. So, a +NAO, alone, should not be a reason to feel there's virtually no chance for a big snow there and in the SE in general in early Feb. The hard data says that's not the case. That doesn't at all mean I'm predicting one though.

Indeed, that's what the model consensus has been showing for several days now with the 60N wind dropping from 50 m/s now to ~10 on 1/28-29. (See model consensus forecast image below.) It would need to get to below 0 to be called "major" as I understand it. That's looking very unlikely now since the models have hardly budged. But this still begs this question: With a drop-off of the winds of 80%, would that be close enough to allow for any potential cooling effects on the SE US to possibly be somewhat similar to what a "major" SSW would tend to cause, especially considering that the Arctic warming looks to be very strong? I mean if it doesn't get all the way to 0, why would that totally cancel out the potential effects?

Yesterday's 12Z EPS mean had been the coldest run yet for the SE in the 11-15. Then today's 0Z backed off some. But now the new 12Z is back to at least as cold as yesterday's 12Z, and even slightly colder at times. For example, yesterday I had noted that the 12Z mean had Charlotte at 30 as of 12Z on 2/4, which was 10 colder than just three runs earlier. Then today's 0Z backed off some to 33. The brand new run has 29. This is significant because this is near the period that some GFS runs/GEFS members are sniffing out a somewhat elevated chance for wintry precip. Looking at wintry precip., this new run's mean has a good bit more than yesterday's almost as cold run and this is mainly for inland areas though the NC coast, especially upper, has a bit of a signal.

The 12Z GEFS mean has about the most wintry precip over the well inland SE overall (not for my and other coastal/deep SE areas) as any other GEFS run in early Feb. The precip falls anywhere from Feb 2nd through 7th depending on the member/area. That doesn't mean there will necessarily be anything significant or that it is necessarily likely. I'm just saying what the mean has compared to earlier runs. This doesn't say what % of the members have it nor does it take into account model bias this season. But it probably means a slightly increased chance vs earlier for well inland areas of the SE.

Yeah, cluster 1 (31%) is sort of the statistical "mode" of the four clusters. However, if ensemble mean bias were to also be taken into account, I think the true chance would be lower than 31% as there's often been too much west coast ridging/E US troughing overall this winter in the 11-15 resulting in a cold bias in the SE/E US. In other words, I think that if model bias were to be incorporated, the bias corrected cluster 1 would be reduced substantially from 31% and some or all of the other three clusters increased.

The 6Z GEFS mean is the coldest GEFS mean yet for Feb 3-5 in the SE (mainly MB) though the 0Z EPS isn't as cold as yesterday's 12Z, which was the coldest EPS so far. The 6Z GEFS is actually colder than yesterday's 12Z EPS. Edit: The mean Arctic surface high track on the 6Z GEFS during that potentially very cold period is through the Ohio Valley to the NE US, which is pretty close to the optimal track for potential widespread SE wintry precip though that doesn't at all mean it would likely occur as I don't think many members actually have widespread wintry precip.

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.