GaWx

Current (as of 12/25 GEFS) AO prog for Dec 2022: -2.60, which trails only 2009's -3.41 and (barely) 2010's -2.63! What does a strongly -AO in Dec suggest for the Jan AO? A very good shot at a sub -1 Jan AO: Strongest 10 Dec -AO/following Jan AO 2009: -3.4/-2.6 6th strongest 2010: -2.6/-1.7 2000: -2.4/-1.0 1995: -2.1/-1.2 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 AVG Jan AO after top 10 Dec -AO: -1.5 So, when also incorporating today's GEFS prog, Jan will likely have a sub -1 AO. In addition, the model consensus is suggesting a +PNA for early Jan that intensifies the 2nd week (just confirmed by the 12Z EPS). The MJO is then progged to be on the left side, which tends to favor a +PNA then. That all suggests a decent shot at a moderate or stronger PNA (+0.50+) in Jan. At KATL, how were temperature anomalies in January when BOTH the AO was sub -1 and the PNA was +0.5+? (12 of them since 1950) 1953, mild +4 1958, cold -4 1961, cold -5 1963, very cold -6 1970, very cold -7 1977, record cold -14 1985, very cold -7 1987, normal -1 1998, mild +3 2010, cold -5 2011, cold -3 2016, normal -1 AVG: -4/cold with 8 of 12 cold and only 2 mild So, this suggests a 2/3 chance for a cold SE US Jan vs the normal 1/3 chance. Thus, despite the progged mild 1st week of January, the above suggests there's a good shot at actually getting a cold month overall. If so, Jan 8th-31st is liable to be very cold in the SE US to make up for the mild first week. Edit fwiw: two of the four non-cold Jan's were during a super El Niño: 1998 and 2016. 1987 was during a moderate El Niño though a moderate Nino tends to be chilly.

After a quite mild first half, it looks like Dec will end up within 1-2 F of normal in much of the SE thanks to a very impressively cold 12/16-12/28! Looking ahead for the SE, it looks like a mainly mild 12/30-1/7 or so before a potential change back to cooler domination starting during the 2nd week in January. Pattern signals are looking favorable for this then with an Aleutian low progged by model consensus to pop the W ridge/ +PNA. This along with the GEFS progging the current +NAO to fall back to neutral/the AO to drop back to negative and the consensus progging the MJO to move to the low to at most moderate amp left side (cold favoring) during the 1st week of January and continuing into the 2nd week tells me that this upcoming mild is likely going to be temporary. My 3rd year cold ENSO analogs had suggested as I stated in the winter forecast thread that one cold month, one near normal, and one mild month would be the scenario to bet on. With Dec being the near normal month, this would suggest one cold and one mild month to come. We'll see. Edit: 12Z EPS falling in line with the above thinking and looking favorable for cold to return during 2nd week of Jan

Look at what has occurred in parts of central and even south FL this morning from the first (weaker) of the two post cold front upper level disturbances! Also from MLB NWS: ISSUED AT 1049 AM EST SUN DEC 25 2022 A SMALL BAND OF PRECIPITATION FORMED OVER EASTERN OSCEOLA COUNTY AND PUSHED ACROSS CENTRAL BREVARD COUNTY AND OFFSHORE LATE THIS MORNING. TEMPERATURES WERE COLD ENOUGH TO PRODUCE A WINTRY MIX OF LIGHT SNOW AND SLEET, FROM VIERA TO MERRITT ISLAND, COCOA BEACH AND CAPE CANAVERAL. MAINLY TRACE AMOUNTS HAVE OCCURRED WITH RAPID MELTING. Here's a link to video evidence of wintry precip: https://twitter.com/realTimB/status/1607043178372243457/mediaViewer?currentTweet=1607043178372243457&currentTweetUser=realTimB In addition, Immokalee in SOUTH FL a little before this reported "MIX PCPN" at 10 AM! IMMOKALEE MIX PCPN 39 27 How often does it rain with it as cold as 41 in West Palm Beach at noon?!? W PALM BEACH LGT RAIN 41 32 70 NW13

From noon, KSAV ended up warming a much faster than models 7 F from noon to a high of 33. But that was still a record low high for the date. Also, the 33 with mainly sunshine means only two mainly sunny days since the 1870s had colder highs in December: 27 on 12/25/1983 and 32 on 12/29/1894. Hunter AAF and my house also had highs of 33. I took two walks (one last evening and one two hours ago) with temperatures in the 28-30 area and wind chills in the teens. Yes, I was the only crazy nut walking around in the two parks I went to, but I loved every minute of them! These were about the coldest I've ever taken in this area. I'm now at 28.8.

Low of 19 this morning. The temp here just before noon was 28.4. At KSAV, it was only 26 at noon. The 12Z GFS, which was about the warmest model run, had them then at 30. So 4 too warm and it projects a high of 32. The only model too cold then was the CMC's 25, too cold by one. It projects a high near 28. The ICON is near perfect with its 26-27 at noon. It projects a high of 30. So, the consensus is for a rise of 2-3 from noon with no more than a 4 rise. All of this implies a good chance of a KSAV high no more than 30 as it stands now. When was the last time KSAV had a high of 30 or lower with mostly sunny skies? Jan 21st of 1985 (27)! The last sunny Dec day at least that cold was 12/25/1983 (27). No other Dec day with no precip other than 12/25/1983 going back to the 1870s had a high of 30 or colder!! What's also amazing is that Ft. Pulaski right on the coast was only 25 and buoys 41004/8, well offshore SC/GA, were only 29/31 at noon!! And that was over SSTs of 70/60!

It was 31 here and throughout the area at 9PM. It hit 32 here near 8:30. The forecast low at KSAV is 17, which would be the coldest since 1/24/03!

I found three more but don't know that any can be trusted or even recognized, especially since they're all well up in elevation (over 3,600 feet) just like Helena: links to last 7 days: 1) Ruby Valley Field (KRVF) : 1066.62 on 12/22 at 7:35 AM MST https://www.weather.gov/wrh/timeseries?site=Krvf&hours=168 Dec 22, 7:35 am -31 -38 67 N 0 SCT026 SCT031 1066.62 25.65 30.59 2) Ennis Big Sky Airport (KEKS): 1065.65 on 12/22 at 9:55 AM MST: https://www.weather.gov/wrh/timeseries?site=Keks&hours=168 Dec 22, 9:55 am -29 -38 60 N 0 10.00 CLR 1065.65 25.02 30.51 3) Ravalli County Airport (KHRF}: 1059.57 on 12/22 at 8 AM MST: https://www.weather.gov/wrh/timeseries?site=Khrf&hours=168 Dec 22, 8:00 am -24 -29 75 SE 5 10.00 BKN031 BKN039 1059.57 26.81 30.64

I have 39.2 after being only in the lower 40s earlier this afternoon.

From best I can tell, I'm guessing no records and high 1050s, which would not be a record despite still quite possibly being the strongest high since 12/1983. I can tell you that the highest for MT, IF this link to hourlies at Helena has accurate SLP data, is at least 1056.5 mb (this says that occurred at 8:53. AM MST on 12/22): https://w1.weather.gov/data/obhistory/KHLN.html 2208:53Calm1.25Fog/MistFEW002-31NANANANA30.711056.5

Although model consensus is keeping any surface low pressure too far offshore to give the deep SE wintry precip 12/26-7, the clipper associated with the 2nd upper level disturbance is giving accumulating snow (mainly light) to some areas well inland in the SE per the consensus between the PM of 12/26 and the AM of 12/27. The 12Z UKMET fwiw gives a portion of N AL and much of N central to N GA accumulating snow late Mon afternoon through Mon evening with as much as 1-1.5" Anniston, AL, to LaGrange, GA, and 0.5" in the SW ATL burbs to near the airport. Previous runs had nothing like this. Temperatures preceding this on Monday only rise to the middle to upper 30s after lows well below freezing. The 850s are a bit below freezing. Thus, the air and ground will be plenty cold enough. So, Monday afternoon and night could get quite interesting in parts of the SE. The disturbance leading to this clipper is not even going to reach the Pacific NW/SW Canada coast for another 36 hours. So, lots of uncertainty remains for something only 3.5 days away. Edit: But the 12Z Euro says it is still too dry for snow.

Today's 12Z model consensus, if anything, is a bit further from SE significant wintry precip 12/26-7 vs yesterday's runs. With it now being one day closer, the already pretty low chances have dropped further. I would have expected something more showing up by the 12Z runs today, like a closer to the SE coast surface low formation, if the trend were heading toward a threat. Yesterday was sort of headed toward that but today has backed off.

I just noticed that the following thread is addressing the very strong cold coming in starting tomorrow:

Although the 0Z Euro still doesn't give the SE wintry precip, the 2nd disturbance is stronger (more closed off) and a little further west for the same timeframe vs the 12Z. This results in the sfc low forming near the Bahamas on 12/27 being a little further west. As a result, rain gets further north in FL to St. Augustine vs Daytona on the 12Z run and to the coastal waters of the Carolinas vs 100 miles offshore on the 12Z. This run does nothing to sway me away from the possibility of later runs giving the SE wintry precip from this.

Latest highest SLP in MT is ~1053 mb. Keep in mind that this isn't based on station measured pressures as they have to be converted to SLP and much of MT is up several thousand feet. These SLPs will be rising considerably tonight. I can already say that the UKMET is going to verify way too low. This makes me wonder about how it converts to SLPs. Something's off bigtime. Map with current SLPs: https://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=11&parm=pmsl&underlay=1&source=1#

Aren't you from the guy from world famous Waycross who moved to Hawaii because you had joined the military? And you were going to do something related to meteorology. Welcome back! I remember you had a Peppermint Patty avatar like mine. For those who weren't around then, many active members here were changing their avatars to favorite Peanuts characters for a reason I can't recall.

The 18Z GFS has nothing wintry over the SE from either post frontal H5 disturbance. However, similar to the 12Z Euro, it does have from the 2nd disturbance a surface low that forms well offshore the SE coast. If there were to actually be a low that tracked, say, 200 miles west of that track, with about the same amount of cold air, there'd probably be a significant winter event 12/26-27 deep into the SE. Keep in mind that this as well as the Euro low were generated by a disturbance currently 7,000 miles away from us and 4,000 miles off the Pacific NW coast where data is relatively limited and that isn't going to cross the Pacific coast for another 3 days. The pattern is quite complex with the huge Arctic high and another H5 disturbance ahead of this one by just one day. When considering all of this, a 200 mile west shift for something 5 days out isn't hard to fathom. So, though the odds favor no big deal 12/26-7 over the bulk of the SE from either disturbance based on model consensus continuing to keep it mainly quiet, a change to a big deal would not be the least bit shocking.

With the historic cold coming in just two days and affecting the entire SE, I was wondering if someone should start a separate thread just for the cold, itself (like a storm thread but for cold). This would be good for documentation purposes as regards folks wanting to look back at the great cold outbreak of 2022 and how SE members were affected. As regards the significance of this event, it certainly would warrant its own thread just based on its widespread and intense effects. Opinions would be appreciated. If nobody else is interested in a separate thread, then there'd be no need for it. But I recommend it.

Well, we're now only one day away. Here's the 12Z run update for today for the highest SLP in mb in the lower 48 on 12/22 vs runs from 24 hours ago (1064 is all-time lower 48 record back to late 1800s): GFS 1067 (0) JMA 1065 (+1) ICON 1063 (-1) Euro 1059 (-1) CMC 1059 (0) UKMET 1052 (+1) AVG ~1061 (no change) The UKMET is either going to shine or fail with their continued much lower SLP vs other models. If I throw out the highest and lowest, the average is 1061.5 mb. Friday is going to be one of the most dramatic days in a long time for the entire SE! *Edit: The 12Z NAM runs have 1067-8 mb depending on the resolution!

The 12Z UKMET has light accumulating snow over far N AL/GA on 12/26 followed by light accum snow over part of C GA, SC, and SE NC that night.

The 12Z Euro (and last few runs) is trending to somewhat more robust at H5 with the lead post frontal disturbance for early 12/26, but it still has nothing to show for it (too dry) at the surface. This run then has a more robust follow up disturbance at H5 (it is quite impressive) along with it being colder over the SE vs prior runs meaning a later ending window for possible wintry precip. It is faster moving than on the 0Z run and has light snow over N AL from this late on 12/26 to early 12/27. It also has cold rain (39F) as far north as Daytona Beach early 12/27 as a weak surface low forms just NE of the Bahamas. These disturbances are still 5-6 days away from the SE and are still well out in the Pacific with a huge Arctic high to precede them. Thus, the uncertainty level for what the SE will or wont experience on 12/26-27 is still high and higher than normal for 5-6 days out.

Thanks. My statement about this being the first run like this was incorrect and I'll edit it out. I had a brain fart as you're correctly pointing out that this timeframe has had a signal on the models for a week now. On the GFS, the 0Z 12/14, 0Z 12/15, and other 12/15 runs had significant wintry precip going deep into the SE late 12/25 through 12/26 and I even posted clown maps for three of these runs lol.

Yesterday's and this morning's cold rain (much needed) was by far the heaviest here in months with 1.50"!

Fwiw regarding the first post frontal upper level disturbance, the 12Z GFS has on 12/26 snow virga over far S MS at 6Z, S and C GA at 12Z, and at the NC/SC border near the coast at 18Z. This is not the first run doing something with this as several GFS runs on 12/14 and 12/15 had significant wintry precip deep into the SE late 12/25 into 12/26. Is this a sign that this disturbance could do more over land in future runs ~12/26 being that this is still 5 days out in a complex/highly anomalous pattern? FYI, this run has a 1067+ mb high over MT on 12/22. The alltime record is 1064. It is very likely overdone somewhat, but even so we're still looking at a good chance for the strongest lower 48 Arctic high since 12/1983. Any opinions? *Edited for corrections regarding past GFS runs for 12/26

Based on the pre-Euro 0Z model consensus, I'd say we're no closer to eliminating the possibility of significant winter precip in the deep SE ~12/26-7. As a matter of fact, this GFS run was the closest call in several days. We're still 5-6 days out and lots can change on the modeling in this highly complex setup that likely includes the strongest SLP in decades. Keep in mind that the energy associated with the 12/26-7 threat is still thousands of miles offshore the US west coast and won't be coming ashore for nearly 3 days.

Besides the strong cold, itself, it looks like to me as of now that there are two packets of energy that the models are harping on after the cold arrives: - one that hits the NW US coast late on 12/23 followed by a dive down to the Gulf compliments of the +PNA and with it affecting the SE to a quite unknown degree ~12/26-7, when it is still cold enough for potential wintry mischief - one that hits the NW US coast only one day later that also dives and then affects the SE to an unknown degree ~12/27-8, when the air modifies enough such that wintry mischief wouldn't be as easy to occur in the more southern areas And then we have a highly anomalously strong Arctic high (possibly the strongest since 12/1983) with Siberian origins in the mix. So, it isn't a simple pattern for the models to resolve over the next 8 days or so. Keep in mind that the two aforementioned packets of energy don't leave the relative data deprived ocean for still 3-4 more days.