GaWx

This afternoon was more like normal here for winter with temps only in the 50s along with a nice easterly breeze and lots of clouds.

Ensemble means as you must know are much more credible that far out. The 12Z EPS, whereas it isn't quite as cold as the 0Z EPS, it doesn't have the SW trough/SER and is thus much colder than the operational.

The latest GEFS forecast for AO implies a good chance for a ~-3 AO for 12/16-31. Since 1950 (assuming I didn't miss any), the only lower AOs for 12/16-31 were in 1950, 1976, 2000, 2009, and 2010. So, 2022 is aiming to have the 6th lowest AO for 12/16-31. 1995 was just above -3 and would be 7th lowest if this forecast holds. Since 2010, there have been none that were -2 or lower. What were the SE US temps and wintry precip for those 12/16-31s? I haven't checked that yet. If I get time, I'll look them up.

Several (~5) 18Z GEFS members have a significant wintry event in this area, something not seen often on model runs. Significant wintry events (say ~1"+ of snow/sleet and/or ~0.25"+ of ZR) have occurred here only ~once every 10 years. So, when these show up on models, they get my interest and they're fun to see but I take with a grain as they more often than not don't materialize. The last two significant wintry events here were biggies: Jan of 2018 and Dec of 1989. The models did a pretty good job of forecasting Jan of 2018 with the ICON doing best here. 18Z GEFS mean (treat these as 10 times wintry qpf as some of this is sleet or ZR rather than snow):

For the record/entertainment way out in the fantasyland period, the 18Z GFS has for here snow flurries on 12/24 from one coastal followed by a whopping ~1" of qpf in the form of sleet/freezing rain on 12/27 from the next coastal. (Some clown maps have this as snow, which it obviously isn't since 850s are clearly several degrees over 0C.) That 1" of qpf of IP/ZR would be the worst here since the devastating icestorm of 1/25-26/1922, the predecessor to the deadly Knickerbocker Storm that hit DC.

18Z GFS is about the coldest GFS run yet for the days just before Christmas.

It still looks like cold is coming, but I want to clarify my post regarding the NG market's 7% drop back since early this morning after the huge (10%) rise last evening. On a national basis (not specifically SE), the three major 12Z ensemble means were all somewhat less cold overall than their 0Z counterparts on the full 2 week runs. So, in summary, the ensemble means are still significantly colder than they were on Friday, but they're all not quite as cold at 12Z vs 0Z today for the full 2 weeks in the US as a whole.

The trend of the 6Z and now 12Z model consensus is clearly warmer vs the 0Z/18Z models. Look no further than the NG price, which went back down 7% from its highs early this morning. Keep in mind that it opened up a whopping 10% Sun evening on much colder models vs Fri PM. Now a good portion of that has been given back.

The TT 12Z GFS map posted below has Alexandria, LA, getting down to -4 F as of 12Z on 12/25. Their coldest on record in December is +7 F (1989) and their coldest on record for any month is +3 F (1899). There's no way this can be anywhere close to real considering that history as well as the run on TT having no colder than ~+13F at Tulsa, OK, for example, from this airmass (on 12/24). Tulsa's all-time coldest in Dec is way down at -8 F (1989), which compares to Alex.'s coldest in 1989 of +7 F. So, in 1989, Tulsa's coldest was 15 colder than Alex, which makes sense. But the 12Z GFS has Alex. ~17 colder than Tulsa's coldest for this airmass. In other words, the 12Z GFS, itself, isn't progging anything near a historic airmass well to its NW but it then gives Alex. an alltime coldest Dec by 11!! I call BS:

Looking at the climo of the other eight 3rd year cold ENSO winters since the mid 1800s: 1) Winter of 1894-5: mainly Feb of 1895 (but also the last week of Dec/first few days of Jan) 2) Winter of 1917-8: Dec-Jan of 1917-18 These were two of the most historic lengthy periods on record in the SE US in terms of a combination of multiple wintry events and persistent extreme cold. For example, Dec of 1917/Feb of 1895 are RDU's coldest Dec/Feb and ATL's 2nd coldest Dec/coldest Feb on record. Also, Feb of 1895 is the snowiest ATL month of any on record due to not just one but two major snowstorms along with a third one! In addition, ATL had two major winter storms in Dec-Jan 1917-8. But I'm not just talking about well inland/northerly locations like RDU and ATL. I'm also talking about locations not at all accustomed to this that are far to the south, including right on the Gulf and SE coasts. N.O, had a historically very heavy snow in Feb of 1895. Right here Feb of 1895 was both the coldest Feb on record and it gave a very rare ~2" of snow (that much accumulation has occurred on average only ~once every 20 years). Dec-Jan of 1917-8 had not one but two accumulations. Both were 1/2" or smaller but only ~1/8 of winters have gotten ANY accumulation. Dec of 1917/Feb of 1895 were the 4th coldest Dec/coldest Feb on record here.

To give you an idea of how much colder the model consensus for especially the E 1/3 of the US is now vs what it was Friday at 12Z, the natural gas market this evening opened up a whopping 10% over the last price traded of Friday!! That's almost, if not totally, unheard of in the 30 years this market has traded!

Some interesting climo for major Atlanta ice and sleet storms based on my own research done several years ago: 1. Every one since Feb of 1979 has occurred when the MJO was within the COD with one exception: the Feb 1979 sleet, which started in phase 3 just outside. But then even it moved inside for most of it. 2. Every one since 1940 had predominantly east winds, not NE winds. Any major winter storm that had mainly NE, N, NW, or west winds (~18 of them) was mainly or all snow as opposed to mainly sleet or ZR.

12Z GFS fwiw has not just one, not just two, not just three, but FOUR different short waves that produce wintry precip over LA. Details that far out (1-2 weeks) aren't important due to very low credibility of the very jumpy GFS. But this shows the potential threat for wintry precip in parts of the SE US at some point(s) in the second half of December. Looking at ensemble consensus for then, practically the entire US is a cold island sticking out like a wintry thumb, which is rare. If enough of that cold were to reach the SE US, it could easily mean significant wintry precip in parts of the SE and quite possibly more than once, especially as usual in the more favorable northern parts. Down my way, where wintry precip is rare (only about once every 4-5 years longterm average and more often trace or light than not), I'm mainly just wanting a cold pattern. Down this far SE, I don't live or die based on getting wintry precip as I'd be dead almost all of the time lol though I never give up hope for a miracle when it is cold. The indices per today's GEFS forecast for that period are rather favorable for cold overall with a continued strong -AO (-2 to -3), weak to borderline moderate -NAO (-0.25 to -0.50), and a rising PNA from the prior three weeks of -PNA to a neutral to possibly weak +PNA during this period. Also, the MJO is pretty conducive for then per forecasts for allowing cold with it mainly low amped inside the bottom part of the circle although the EPS has it going outside right side in about 10 days, which itself would favor mild in the SE.

This month the AO plummeted to just below -4. The NAO plunged to -1.95 while the PNA fell to -1.86. For all months since 1/1950, there's only one other month that had a sub -4 AO day that also had BOTH a daily PNA at least this low AND a daily NAO at least this low: December of 2010. Its AO dipped to -5.3, NAO to -2.0, and PNA to -2.1. So, a more extreme for all 3, especially the AO.

Here's something one will see only very rarely, a 360 hour EPS map with BN essentially in all of the lower 48! It is especially hard for all of Florida to be included in these situations, where usually some ridging nearby keeps it at least normal especially in S FL. Note also that this is for Christmas morning:

We're pretty much on course for a cold most of 12/16-20 in most of the SE. Shortly after, we warm to normal to above for ~2 days at least. So, I'd like to look further: Take it with a grain considering recent models being too cold in the 11-15 day period, but fwiw the 12Z EPS is decidedly colder at 850 mb and the 500 mb pattern is also more conducive for it to not warm up as much or for as long after the aforementioned brief warmup. It suggests cold likely returns to much of the SE by 12/23. Again, fwiw! But I prefer models showing this as opposed to not because I would strongly prefer the return of cold over the warmth of the first half of this month!

The 6Z GEFS was about the coldest GEFS run yet in the SE in general for 12/16-20 and the 12Z is almost as cold. Looking ahead to after that period (11-15), here's some food for thought regarding models recently being too cold to keep in mind when looking ahead from a non-hyping pro met company (Maxar) (unlike the hyping Bastardi): "These are larger swings and much is due to poor model performances of late. As an example, here is how the past five days verified:" This is much warmer than the model consensus had when this period was 11-15 days out. "Looking into these errors, we found that the models underestimated the warmer influence from tropical circulations. Our method was to find MJO cases which also featured the already established –AO. These cases decently matched the upper air pattern that was observed and provides proof that the MJO had a role in what was a warmer period for the Eastern Half. " "We can’t guarantee that the models are mishandling this forcing again, as one case does not necessarily represent a bias that will continue. That said, the MJO looks to return to those warmer phases within the 11-15 Day period, and this contributes to our forecast leaning warmer than the models for the South and East during that period." "The alternative is based on model projections at 500mb. The upcoming cold pattern is due to a strong polar ridge, with signals like the –AO and –EPO. As of now, the models show colder than normal air reaching the South and East, at least for a few days, but are more anomalous from the Northwest to the North-Central:" "When we look at the –AO and –EPO correlations, they imply a colder risk for the South and East as well:" "So mixed signals is the message here, between the warmer forcing from the tropics to the colder pattern signals being projected. Confidence is lower than usual as a result."

Impressive! That's the warmest so late in the season by a full week! The only other day this warm in December on record back to 1878 was 79 on the first. Not a total shocker though with such a strong -PNA.

Per 12Z EPS temperatures for deep SE: warmer than normal most days through 12/15; cold (below to much BN) 12/16-19; back to warmer than normal 12/21-22 followed by cooling back to normal 12/23 with potential for cooler soon after The model consensus is pretty set on a cold snap for 12/16-19 after the mainly mild next week or so. The main question is whether or not we get another cold snap during the last week of the month. There likely be will be plenty of cold to our NW, but will a decent piece of that reach deep into the SE? It won't be easy. If it were to do so, there'd be a small chance for December as a whole to end ~normal as opposed to AN. It would take quite a bit of cold then to help negate the very warm 12/1-15.

It is 81 F as of 1PM at both major local reporting stations (maybe KSAV has been fixed?). As of the same time yesterday, KSVN was at 82. The alltime December record high is 83. So, we'll probably not quite reach that.

12Z GEFS 174 vs 0Z 186: 500 mb ridge centered significantly further east on 12Z from NW Canada down to just off the west coast vs Alaska down to well off the west coast on the 0Z. As a result, the mean Arctic surface high centers are further east in NW Canada vs the 0Z. We'll see how the rest of this run evolves, but this is potentially a better setup vs the 0Z if you're wanting a sustained +PNA or at least a less -PNA, which would be more conducive to more sustained cold in the SE US setting up soon after this. Edit: This results in the 12Z GEFS being the coldest run in many days for the SE US starting 12/18.

The GEFS from 24 hours ago (0Z of 12/7) was suggesting we could finally get a sustained +PNA starting ~12/23. The new run (0Z of 12/8) says no sustained +PNA in the foreseeable future with the ridge instead staying offshore in the E Pacific. Delay, delay, delay...that has been the theme for quite awhile. Edit: 0Z EPS concurs that there will be no sustained +PNA pattern through 12/23. It has a cold snap ~12/16-8 with warming afterward, especially deep in the SE where slightly warmer than normal 850s return late and what looks like a La Niña favoring SE ridge possibly rebuilding near the end of the run. Like I said earlier, I'd be quite content if I can get a near normal last half of Dec in my area (especially if we could get dews mainly 40s and lower instead of the current/recent 50s to low 60s dews). In other words, something resembling winter unlike the first half of this month.

Not down in GA/most of SC though I wish that were the case. Most of 12/8-15 (at least) is forecasted by model consensus to continue significantly warmer than normal as the -PNA dominates. It is after that that we'll finally have a chance for near to possibly BN to dominate deeper into the SE for an unknown period as the PNA rises to at least neutral. We're headed for a very warm first half of December here, similar to 2021, 2015, and 2012 of the ones over the last ten years. How were those three's last half of December here? -2012: normal -2015/2021: very warm/warmer than first half! So, as one who prefers colder than normal and considering it is La Niña, I'd take a near normal second half of December in a heartbeat.

I'm not normally a fan of warmth, but it sure did feel good going out today in shorts. We'll have a similar opportunity tomorrow due to similar warmth with sunny skies and light westerly winds again. We may not know today's official KSAV high for a few days or longer, but I'm thinking 82+. KSVN was 82+.

@Awesomesauce81 @gtg947h FYI for the record, the KSAV (airport) automated temperature sensor suddenly became erroneously too warm around the start of this month and is thus supposed to be replaced within a few days per CHS. This is of extra importance now because the 1PM there is showing 85 F, which if real would mean 2 F warmer than the alltime December record of 83. In reality, it is very likely "only" in the lower 80s as it is too warm by ~3 F. The Hunter (KSVN) station's 82 is likely about what it really is. CHS NWS has human observers there. So, at some point later the official record will reflect what they record. As it is though, 82 would be only 1 F from tieing the alltime December record at KSAV. So, KSAV is already flirting with the 83 monthly record. Strong -PNA/La Niña ftw if you like warmth in December! This was posted starting on December 1st by the CHS office: "EQUIPMENT TEMPERATURE DATA AT THE KSAV ASOS ARE SUSPECT. PARTS ARE ON ORDER AND WILL ARRIVE THIS WEEK. USE DATA WITH CAUTION."