GaWx

Wow regarding the 0Z GFS strat forecast!! Check it out (loop this for the entire run, which gets very interesting from 2/10 to the end): https://www.tropicaltidbits.com/analysis/models/?model=gfs&region=nhem&pkg=Tz10&runtime=2023020500&fh=-12 What is most needed to get out of the neverending ugly pattern is major chaos. One potential source of major chaos is the strat. The chance of strong AO/NAO blocking goes up significantly 10+ days after a major weakening of the SPV. This run's strat becomes about as chaotic as one would want. If something close to this were to verify, there'd be no telling what would happen in the SE starting as early as the last week of Feb, especially considering MJO forecasts.

1. The string of GFS runs with what appears to be a major SSW/reversal of 60N winds at 10 mb from W to E is now at 8 as of today's 12Z. As opposed to being out of touch, the GFS appears to be leading the GEFS/GEPS as they're continuing to play catch up with the GFS. See section 2, below. Also, very importantly, the modeled SSW is moving up in time, which means an earlier onset of potential impacts in the SE than thought earlier. More on this timing in section 3. 2. The GFS leading the way is evident when comparing the two images below. Going below the 0 line on the "Zonal Wind Mean" map (top map of each image) is what's needed for a "major" SSW. As of the top image from 3 days ago (1/31), the GFS was already nearly forecasting a major with it down to +1 m/s on 2/15. Note that it was an outlier with the GEFS/GEPS way up in the +15 to +20 range. Now, look at the 2nd image, which is from today. The GFS is firmly forecasting a major with a low of -10 (2/16). And look how far the GEFS/GEPS have dropped: to close to 0! So, even the GEFS/GEPS are bordering on a major. Based on these trends, the GEFS/GEPS appear to be heading to showing a major. 3. Now I'll address the earlier timing: On the older map the GFS winds don't get to its low of +1 til 2/15. In contrast, today's map has the GFS already to a major on 2/13 due to a steeper drop and lower starting point. That's 2+ days earlier! The old GFS was still up at +15 on 2/13. Regarding temperatures (bottom map of each image), the old GFS showed warming not starting til 2/13 (from 221 K). In contrast, the new GFS' warming starts on 2/9 (4 days earlier) and from a warmer starting point of 224. As of 2/13, the new GFS was already up to 230 or 9 warmer than the old GFS. Also, the old GFS was still warming as of 2/16 (reaching 230 three days later than the new GFS). The new GFS has already peaked on 2/15 (at 237), when the old GFS was still down at 225. 4. Summary: - Chances for a major SSW continue to increase as the GFS leads the way. As of today's 12Z run, 8 in a row have had a major SSW. - The timing of the forecasted SSW has moved ~2-3 days earlier vs what models were showing just three days ago. This means an increased chance vs what was earlier thought for cooling effects on the SE, should they occur, to start during the last week of Feb as opposed to the first week of March. Images of strat winds/temps: GFS in orange Older (based on 1/31 runs): New (based on 2/3 runs):

Even way on down here near the coast, where there's a T+ of wintry precip on average for the entire winter only once per 4 years, I don't give up til after the first week or so of March if the pattern is cold: - SAV's 2nd biggest snow on record was on March 4th! CHS also had a significant snow that day. - Since 1890, there has been wintry precip (most but not all were traces) within the CHS-JAX corridor 15 years during the 1st week of March or once every 9 years on average. That's pretty notable for way down in this stretch at the coast. So, it isn't all that far-fetched to hope for wintry precip in this area in early March. *Edit: Meanwhile, based on the projected MJO timing as well as the increasingly possible midmonth SSW that could exert its influence on the SE more quickly than the average lag, I'm not at all discounting the possibility of a cold last week of Feb. IF that were to happen, many more doors would open regarding the chance for SE wintry precip. A cold 2/22-3/7 or so would be quite interesting. The highly expected strat warming along with a very much weakened and displaced SPV introduces a lot of chaos and thus the possibility of a real pattern change! Buckle up, folks!

Because it is a potentially a game changer for the seemingly never-ending dreary SE pattern late this month into early March, especially when combined with what may very well be a favorable MJO and considering that wintry precip climo is still near peak into the first 3 or so days of March, I expect to keep talking about a *potential* major SSW at midmonth as long as the threat shows on the models. The 12Z GFS is the 4th run in a row with a *major* SSW on it. Keep in mind that the SSW that just occurred didn't make "major" status, which requires a reversal of 10 mb winds from W to E at 60N. Typically that requires a high dominating the Arctic instead of the SPV. This last one's high didn't get there and allowed the SPV to remain too close/too strong despite the impressive warming. We'll need to see if the GFS holds onto a "major" SSW as we get closer. If it is still there 5 days from now, I'd then be very excited. In the meantime on the GEFS, the N Pole at 10 mb has warmed as of 0Z 2/15 from -64 C on the 0Z 1/26 run to -34 C on today's 12Z run. So, it has warmed a whopping 30 C (54 F) just within 7.5 days of runs at the N Pole for the same forecast point (2/15). So, the GEFS continues to trend in a SSW direction as the crucial period gets closer and the ensemble gets more of a clue. Edit: 18Z GFS appears to me to be 5th in a row with major SSW

Phil (not Hogtown Phil lol @pcbjr) must have seen the 6Z GFS' ~35C (63 F) 10 mb warming at the N Pole within 60 hours (6Z on 2/14 to 18Z on 2/16). That's pretty sudden! It also appears to have a 60N wind reversal at 10 mb from W to E with the high in the Arctic. So, I have these four GFS runs with a major SSW (60N wind reversal) very likely being depicted at 10 mb at midmonth: 18Z of 1/31, 18Z of 2/1, 0Z and 6Z of 2/2. So, three GFS runs in a row. **Edit: 12Z GFS makes four GFS runs in a row

Although earlier in the month (like the timing of the current minor SSW) would have been optimal, this later one definitely wouldn't be too late to potentially have significant downstream effects in the SE outside of the mountains. Yes, likely ~2/25 or later for first effects should they occur. The key would be getting the effects in the first place and then getting them to start quickly enough. If they can start 2/25ish, that would give many in the SE still another week or so of prime climo to work with. After all, March 2nd has had more SN/IP at RDU than any other day if I'm not mistaken. If the start of any effects is delayed til, say, March 10th, then it likely wouldn't do much good though even then there could be some benefit. Edit: The 0Z GFS joins the prior two 18Z GFS runs in having what appears to be a major SSW at midmonth.

If this isn't a major SSW on the 18Z GFS at 10 mb, then I don't know what one is: high in the Arctic has replaced the SPV with E winds at 60N all around it, the Arctic is much warmer than normal, and the SPV has plunged WAY south to 50N with it stretched/splitting. I know this is just the GFS late in the run (very unreliable), but the trends the last few days have been headed toward a midmonth disruption/warming. If this were an isolated GFS run showing this with no prior support of strat changes at midmonth, I wouldn't have posted thi:

The high at KSAV was 82, three shy of the record and the warmest since Dec 8th's 82.

The table (SSW plus MJO) per models is being set for this scenario though it could start during the last part of Feb. I just did a time lapse on Tropical Tidbits of 0Z GEFS runs at 10 mb for the forecast date of 2/15 starting with the 1/26 run and ending with the 2/1 run. It clearly shows a continuing trend of a further S SPV along with a further N high. The further S the SPV and the further N the high, the more the disruption/warming. The 2/1 run location of the SPV on 2/15 is ~700 miles S of the 1/26 run's position, which was near Svalbard (80N). Now it is over N Norway (70N). Also, the main high as of 2/15 has moved 700 miles N from S of Alaska (55N) on the 1/26 run to Alaska (65N) on the 2/1 run. Along with this, the N Pole at 10 mb has warmed as of 2/15 from -64 C on the 1/26 run to -42 C on today's run. So, it has warmed 22 C just within 6 days of runs for the same forecast point (2/15). So, the GEFS has gone from showing nothing interesting in the strat 6 days ago (cold SPV over the Arctic) to a significant disruption/warming today for 2/15. That's why I didn't start talking about this new warming til yesterday. And the trend toward more disruption/warming on future runs may not be over.

The main hope I have for a cold last week of Feb into early March largely hinges on the degree of strat Arctic warming and disruption of the SPV at midmonth. GEFS runs since 12Z yesterday have continued to show significant warming along with a southward displacement of the SPV to N Scandinavia at midmonth. This is the kind of strat chaos that can shake up the pattern enough based on past cases to lead to a couple of week+ colder pattern in the SE that would start within 10-14 days of the "onset" of a SSW. With that kind of timing, any SSW generated cold could make it to the SE as early as during the last week of Feb. The MJO would likely be in a more favorable position at late month into early March to help out. Meanwhile, model consensus is still suggesting a short moderate cold snap ~2/11. The 12Z Euro *fwiw* even gives parts of NC several inches of snow then.

I agree to some extent since any cooling effects from a possible major SSW in mid Feb could easily extend into mid to late March when normals are a good bit higher. However, there'd still be hopes for a colder late Feb into early March. First, looking at non-El Nino years with a SSW in mid-Feb: Consider the cold that followed the 2/17/2002 SSW, which was 2/22-3/6. Also, the 2/11/2001 and 2/12/2018 SSWs had cold follow 3/5-4/3 and 3/3-3/15, respectively. So, there's some early March cold included with those last two. Looking a bit away from mid Feb: Late Feb: 2/22/1979 and 2/22/2008, I couldn't find any cold dominated period of note. But 2/21/1989 had cold dominate 2/23-3/9. Early Feb: 2/6/1981 had cold dominate 3/6-25. So, in summary, this all tells me that if there's a major SSW, potential cold could come in as early as the last week of Feb. The last week of Feb and first few days of March are still pretty cold on average (within only 5-6 of the coldest week in January) and are also within the climo active period for SE wintry. By the way, the 0Z GFS is another run with an impressive displacement of the 10 mb SPV!

Fwiw, the 18Z GFS, like the 0Z, has what may be a real live major SSW on it late in the run fwiw. For those curious, check out the N Hemispheric maps at 10 mb late in the 18Z/0Z GFS runs to show what I'm seeing. They show a significantly displaced SPV along with massive Arctic strat warming. These are both bordering on a 60N wind direction reversal from W to E, especially the 18Z.

If RDU's total were to remain at a T, it would be the first time that low since 2005-6 for those who didn't know.

There's increasing model support for a transient cold shot into the SE ~2/11. Let's see how this evolves.

Recent GEFS/GEPS/GFS runs are suggesting the possibility of a rewarming Arctic strat. toward midmonth along with another drop in the 60N winds. Link to follow the Arctic strat temps/60N winds: https://stratobserve.com/ens_ts_diags This doesn't mean I'm forecasting another SSW. (The most recent SSW ended up being "minor".) This is just something I'm following. If a significant rewarming/drop in 60N winds actually looks like it is going to occur, I'd expect to be discussing this more and more down the road.

The UKMET, which had as much as 0.5" of ZR in parts of N GA/NW SC on Sunday on the 12Z run associated with a weak NE GOM surface low, has on the new (0Z) run no surface low due to a much weaker wave at H5. The result is much less qpf in GA/SC (under 0.1"), warmer temperatures, and no wintry precip.

The 12Z UKMET has a bigger deal than other models in parts of N GA and NW SC Sunday morning. At Athens, GA, qpf is ~1/2" and temps are near 32. Thus on the border of 1/2" of ZR, which would be close to a scattered power outage situation. Keep in mind that wedged cold air is often underdone and thus colder as well as a larger area of sub 32 wouldn't be a surprise. Clayton, GA is 31-32 and gets ~.15, which may be sleet based on 850's near +3 C:

To show how much the ICON has been trending colder into the SE resulting from the Arctic high bringing record breaking cold into the NE this weekend, here are the SLPs at Columbia over the runs of the last few days as of 10AM on Saturday 2/4: 1/28 12Z: 1019 mb 1/29 0Z: 1033 mb 1/29 12Z: 1033 mb 1/30 0Z: 1033 mb 1/30 12Z: 1037 mb 1/30 18Z: 1040 mb!! That's 30.71"! The 18Z ICON has a freeze all of the way down here that morning after being down only into the low 40s on the 0Z run.

I got ~2" since yesterday! Over the last 9 days, I've gotten ~4", which is about as much as I got from November through Jan 21st thanks to La Niña induced dryness! This is helping the drought conditions immensely. Kudos to the Euro and others for picking up on this El Niño-like wetness late this month.

Looking more closely at the ZR on the 12Z GFS for late Saturday night til ~noon on Sunday, it has mainly <0.25" from the NW half of SC to central NC. However, it does have a smaller area within this of 0.25-0.45" between Charlotte and the Triad. It gets as cold as upper 20s in Charlotte with the ZR. The GFS also has snow (850s below 0C) to the NW of this area.

The 12Z Euro has a high on Saturday (2/4) not getting above 32 in Raleigh. The coldest of the weekend is low 20s on it. This is looking to easily be the 2nd coldest airmass of the winter to date there and in much of NC. In addition for ice fans, there are hints on the models (as per the GFS post above) for some ZR in NC, northern SC, and NE GA (most likely not heavy enough for outages but more of a travel hazard if it occurs) on Sunday though I don't see any on the Euro. Regardless, this weekend is looking to be cold in the SE with record cold in the NE.

That's what the latest CFS thinks lol. After the extremely cold NE shot this weekend, it has a break for 12 days before 3 more extreme airmasses plunge down between 2/17 and 2/28 in various parts of the US. We know any cold extended portion of a CFS run is pretty much pure entertainment. But this does remind me that we have very little idea about how the last half of Feb will be. After all, Feb 15th is still 2 days beyond the end of the EPS, which itself is very unreliable. And keep in mind what I said about knuckleballs. As we get into mid Feb, that's when we may have an MJO move back to inside the COD and away from the MC. Also, if we are to get a SSW induced -AO/SE cooling, it could easily start then based on analogs. Regarding the very strongest Arctic plunges deep into the SE in Feb, most have actually occurred during either La Niña or cold neutral despite the relative rarity of cold Niña Febs. A good number of these were during 2/8-2/17 although they have occurred as late as 3/7! A good portion of these followed a mild period. The Arctic's coldest normal is not til 2/25! Regarding major snow/sleet in the SE, climo is still relatively favorable through the first few days of March. In RDU, the peak day is actually March 2nd! ATL has had several major winter storms in the first few days of March. Even way down here where big winter storms are very rare, two were between 2/25 and 3/4 and there have also been several non-major wintry events within that period! Just some food for thought.

Followed by a late winter?? Anyway, nothing is certain in the wild and whacky world of wx! Just when you think you've got it figured out, in comes a knuckleball.

I had been hoping that the Euro idea of the MJO going into the circle (which typically wouldn't be a warm signal) before reaching phases 4/5 (which is what GEFS had) would occur in Feb. But it looks like GEFS idea, which favors warmth at midmonth, will win out as the Euro has been inching to the GEFS. Also, the progged +NAO/AO aren't favorable for cold.

Below is a graph showing that the 10 mb winds at 60N dropped sharply from 50 m/s on 1/23 to 12 m/s on 1/28. It needed to drop to <0 to be counted as a "major" SSW. Instead, I expect it to called a "minor" SSW. The models did a good job as they had it drop to this vicinity for a good number of days prior to 1/23. Does it going 75% of the way mean it will still likely have significant cooling effects on the SE starting mid to late Feb and lasting at least a couple of weeks thanks largely to a new long period of -AO? I don't have a good feel for it as the analyses were based on major SSWs. And the model consensus is forecasting some restrengthening of the SPV along with cooling back a good bit in early Feb.