GaWx

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."

This isn't just due to La Niña. It is also likely due to heavy convection in and near the MC, something that has been a factor for at least several years due partially to near record SSTs there.

The 12Z EPS 11-15 is milder in the E US than recent runs with it only down to near normal in the SE vs BN on prior runs. This likely has lead to NG dropping now to session lows (-4% on the day).

1. Agreed. With a cold E US December, NG would likely now be much more expensive! There are clear benefits to a mild winter. 2. Fwiw, a stronger +PNA coming out now on the 12Z GEFS in the 11-15.

1. Yes, the jet crash was in Jan of 1982. During the second week of Jan of 1982, Atlanta was just about totally shut down. First, they had their first below zero F since 1966. Then they had a three day barrage of a heavy mix of wintry precip (front part of this was the infamous "Snow-jam 1982") due to back to back Gulf of Mexico storms followed by a second very cold airmass dropping temperatures back to zero! 2. Just before Christmas of 1989, the SE coast/N FL got a historic snow giving first on record white Christmas to many with a dusting as far south as Sarasota!: 3. Nothing for me on Veterans Day 1987.

I agree about the south to southern mid-Atlantic (pretty strong correlation to cold of +0.5 to +0.6) though it is still a pretty cold signal even up into the SNE with a respectable +0.4 to +0.5 correlation even up there (nearly +0.5 at NYC):

But for many of us down here in the SE US, the 80s was a very wintry decade with quite a few major and widespread winter storms including March of 1980, Jan of 1982, March of 1983, Jan of 1987, Jan of 1988, Feb of 1989, and Dec of 1989. In some parts of the SE, the 1980s had the heaviest liquid equivalent for wintry precip in the better part of 100 years. That extreme cold that deterred snow in the NE US enhanced it further south.

NG market down another 2-3% as of now (~25% down vs Thursday's high!): https://www.investing.com/commodities/natural-gas As previously mentioned, this market is often as good a barometer as any of temperature trends in the 14 day forecast in the E US as a whole. SE cold lovers generally want NG to rise on any day. The trend in the E half of the US and especially E 1/3 in the most recent EPS and GEFS run means often has the most effect though the operational GFS and especially Euro 6-10 can have significant short term effect. Thus, NG is telling me that milder trends since Thursday in the E US over the next two weeks are still not reversing as of this moment anyway. We'll see how the rest of the 12Z GEFS as well as the 12Z Euro suite affect NG over the next few hours. A deadcat bounce is due regardless of the wx outlook.

The 12Z EPS is still another EPS run establishing a +PNA around 12/16-17. So, it has been persistent with this for several days. We'll see whether or not the model will finally be right and the pattern actually change to cold dominated around then. The PNA is forecasted to rise to neutral to possibly a slight positive then while a -NAO per the GEFS at least is forecasted to then be getting reestablished along with a -AO. The MJO per GEFS is forecasted to possibly then be headed toward low amplitude/inside COD on left side, which in combo with a -AO/-NAO/neutral to low amp +PNA would typically be cold in the SE in mid to late December. We'll see.

If you want to know how the 14 day model consensus (mainly GEFS and EPS runs) forecast for the E US is trending from day to day, especially in late fall and winter, a great clue more often than not is the natural gas (NG) market. If warmer/colder than the previous trading day (M-F), it will often be down/up. Currently, it is down a whopping 10% vs Friday's close! Also, it is down an amazing 22% just since the high of the Thursday session, which is only two trading days ago! So, the NG market is telling us that the models have been adjusting much warmer in early to mid December in the E US vs what they showed just 4-5 days ago meaning they've been strongly cold biased. I believe that this cold bias (models being much too cold) is probably mainly the result of intense convection in and near the Maritime Continent and Indian Ocean leading to a warmer pattern vs where the official MJO is. It thus acts like a warm MJO phase for the SE US. The models don't handle this well and thus it has resulted in a cold bias on many occasions over recent years. The intense convection has often been the result of (near) record warmth in that area. For this reason and as long as this too cold trend in the models continues, it is best to be more wary about cold runs than warm runs of models. At some point, this trend will cease and cold will start verifying better. But when? Current NG prices: https://www.investing.com/commodities/natural-gas-historical-data

I think the following might be of interest as I happened to have recently looked at the December 1-15 temperature anomalies at Raleigh-Durham, NC, (RDU) for the seven years since 1950 with an -NAO of -1 or stronger averaged out for the period 12/1-15 (year: average NAO for 12/1-15, RDU temperature anomaly): 1963: -1.5/very cold -7 2009: -1.3/cool -2 2010: -1.2/very cold -12 1977: -1.1/cold -5 1989: -1.1/very cold -7 1995: -1.1/cool -2 2002: -1.0/very cold -9 *Average was a cold -6 *None were mild. All were colder than normal with 5 of 7 cold to very cold. *2010 with -12 was the coldest of these and yet it somehow did this with a PNA way down at -1.0, the 4th lowest 12/1-15 PNA since 1950! The lowest 12/1-15 PNA since 1950 isn't that much lower (-1.2 in 1972). *2022's 12/1-15 NAO/PNA combo is forecasted by the GEFS to end up by far the closest to 2010 vs any other year since 1950. The latest forecast is for an NAO of ~-0.8 to -0.9 and a PNA of ~-1.1. In 2010, the NAO was -1.2 (3rd lowest since 1950) and the PNA was -1.0 (4th lowest PNA since 1950). *But despite the similarity to the NAO/PNA of 2010, the latest forecast temperature anomaly for RDU for 12/1-15/2022 is for it to average significantly warmer than normal, the opposite of 2010's extreme cold! With it only December 5th, the actual 12/1-15/2022 is still somewhat up in the air especially considering that this is a difficult pattern to forecast. Regardless, the period as a whole clearly isn't currently looking cold even with the possibility of it ending cold and thus looks to be far different from 2010. RDU temperatures: https://www.weather.gov/wrh/Climate?wfo=rah Daily NAO since 1950: https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.nao.cdas.z500.19500101_current.csv Daily PNA since 1950: https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.pna.cdas.z500.19500101_current.csv

The end of the 0Z Euro fwiw is by a good margin the coldest in the SE US at 850 mb for any run yet this season. The 240 hour is absolutely frigid at 850 mb with 850 mb temperature anomalies a whopping 10-15 C (18-27 F) colder than normal! I don't have 2m temps yet. Again, fwiw that far out. Runs like this for day 10 don't tell me what's likely or anything close to likely for day 10. They just tell me the kind of thing that potentially can happen, I.e., a small chance for something similar in day 10, especially considering that models have been too cold. Edit: Although not as cold in the 11-15 in the SE as the coldest yet prior run because the 500 mb trough axis is a bit further west, the mean 0Z EPS is still chilly with a +PNA forming. Moreover, with the trough axis near the Mississippi River instead of the SE, this run is more moist and includes a few members with Miller A Gulf lows moving ENE at the bottom of the cold air. I don't have access to mean snowfall or individual members' snowfall, but I bet a couple of members have snow around the end of the run.

Further to the above, I just saw the 12Z EPS and it is I believe easily the coldest run in the SE of any recent run for any 11-15 day period. It is significantly colder than any run of the last few days for sure. At face value, it is hard to beat this run if you like cold. Linking this to my post above, this is the kind of thing that is quite possible with an MJO forecast like what the GEFS has. But the EPS and other models have been too cold during earlier runs for the 11-15 day periods. As I said, I suspect high levels of tropical convection in the MC/IO are at least partial culprits. If that convection were to diminish, then that might reduce the tendency of models to be too cold in the SE and thus allow for cold similar to the 12Z EPS' 11-15 to actually happen. The timing will be crucial to be able to take advantage of the progged cold favoring MJO should it really end up as the GEFS has.

Here is the PNA for the seven strongest -NAOs since 1950 for Dec 1-15 along with the RDU temperature anomaly for the respective Dec 1-15: 1963: +0.8/-7 1977: -0.4/-5 1989: +0.9/-7 1995: 0.0/-2 2002: +1.2/-9 2009: +0.1/-2 2010: -1.0/-12 Here in 2022, the GEFS is now forecasting a Dec 1-15 PNA of -1.1, which would be tied for second lowest since 1950, and an NAO of -0.9, which would be ~8th lowest NAO for Dec 1-15. So, 2022's -PNA/-NAO for Dec 1-15 is actually most similar to 2010, which despite a strong -PNA was the coldest Dec 1-15 at RDU of the strong -NAO group! It is the only Dec 1-15 similar to 2022. Thus as mentioned earlier, this makes for an unusually difficult forecast for the models as well as forecasters. Therefore, my confidence in model runs is lower than normal and I expect continued volatility in model runs. Currently, for the first half of this month, warmth is winning out over cold for the SE US on the recent model runs as runs have largely been turning warmer for the same period. This may be due to enhanced tropical convection in or near the Maritime Continent/Indian Ocean, which tends to act like a warm phased MJO regardless of what the official MJO phase is. This has often occurred in recent years due to record or near record warm SSTs there and has often resulted in model runs being cold biased. This often results in runs showing cold and then backing off in later runs for the same period as it gets closer. Also, La Niña in general favors a stronger SER (southeast ridge) than other ENSO. Whereas La Niña isn't just going to disappear, the enhanced tropical convection that I mentioned can change. I suspect that IF a -NAO/-AO regime were to hold, the best chance for SE cold to take hold for a several week period would be if that enhanced convection were to diminish and possibly allow a +PNA to become dominant. The GEFS is saying to look for a slow moving low amp/inside COD MJO on the left side of the circle to possibly occur starting around Dec 17th. Research has shown that especially during and near midwinter that a slow moving low amp MJO just outside to inside the left side of the COD (especially rotating from 7 to 8 to 1 to 2) has on average been the coldest MJO for the SE US. IF this occurs, IF the -NAO/-AO were to still be around, and IF that convection were to diminish, I'd be looking out for a +PNA to dominate along with a cold 2nd half of this month. Lots of IFs though. So, this isn't a prediction. (Sorry for the big font, but I didn't do that on purpose. I wasn't able to change it using my phone.)

It was a warm day in this area today with highs near 79. Strong -PNA in control.

Today's 0Z GEFS based forecast for 12/1-15 is for an NAO of ~-1.0, which would be about tied for 7th lowest NAO since 1950. The quoted post above shows an average at RDU of a cold 6 colder than normal for 12/1-15 for the 7 NAOs since 1950 of -1.0 or lower. OTOH, today's GEFS based forecast for 12/1-15 is for a PNA of ~-1.0. This would be for 12/1-15 the 4th lowest PNA since 1950 and the lowest since 1973! Here are the RDU temperature anomalies for the six 12/1-15 periods since 1950 with a PNA of -0.8 or lower: 1956 (PNA -1.1): quite mild +7 1961 (PNA -1.05): normal -1 1972 (PNA -1.2): mild +4 1975 (PNA -0.9): normal 0 2012 (PNA -0.8): quite mild +7 2021 (PNA -0.8): mild +4 *Average: mild +4 *None were cold and 4 of 6 were mild to quite mild. So, there is a forecasting conundrum for the first half of this month with the strong -NAO analogs averaging a cold -6 and the strong -PNA analogs averaging a mild +4. This illustrates the complexity of the pattern and thus the higher level of difficulty of the models sorting this out. This tells me to keep confidence in any one model run (including ensembles) lower than normal and to expect larger than normal changes from run to run. --------------------- *Edit on 12/4/22: Although my list of strongest -NAOs for Dec 1-15 is correct, I inadvertently left off 2010's -1.0 from my list of strong -PNAs. Thus, I need to update the -PNA analysis and will do so with today's GEFS based forecast, which is ~-1.1 and ~tied for the second strongest -PNA since 1950 for the first half of December. The GEFS NAO forecast has risen from ~-1.1 to ~-0.9 though that's still strong enough to be ~8th strongest. Here are the RDU temperature anomalies for the seven 12/1-15 periods since 1950 with a PNA of -0.8 or lower: 1956 (PNA -1.1): quite mild +7 1961 (PNA -1.05): normal -1 1972 (PNA -1.2): mild +4 1975 (PNA -0.9): normal 0 2012 (PNA -0.8): quite mild +7 2010 (PNA -1.0): very cold -12 2021 (PNA -0.8): mild +4 *Average: normal +1 So, adding 2010's extreme cold despite a strong -PNA changes the average considerably since it is a near normal +1 vs a mild +4 without 2010. Including 2010 is extra important because it is by far the closest strong -NAO/-PNA analog to 2022 with 2022 ~-0.9/-1.1 vs 2010's ~-1.2/-1.0.

So, are these models right? Or are they underestimating the cold potential of the forecasted -1.1 NAO for 12/1-15? Which is more likely? I don't know but consider this for RDU's 12/1-15 temperature anomalies for the seven years since 1950 with a -NAO of -1 or stronger: 1963: very cold -7 1977: cold -5 1989: very cold -7 1995: cool -2 2002: very cold -9 2009: cool -2 2010: very cold -12 *Average: cold -6 *None were mild. All were colder than normal with 5 of 7 cold to very cold. RDU temperatures: https://www.weather.gov/wrh/Climate?wfo=rah

Per the 0Z 11/30/22 GEFS run, the first half of December is forecasted to have an average NAO of near -1.1. That would by a good margin be the strongest -NAO in the first half of December since 2010. Looking back to 1950, here are the strongest -NAOs for the first half of December: 1. 1963: -1.5 2. 2009: -1.3 3. 2010: -1.2 4-6. 1977, 1989, 1995: -1.1 7. 2002: -1.0 The remainder since 1950 are -0.8 or weaker. So, based on today's GEFS, 2022 is looking to be at about tied for 4th with 1977, 1989, and 1995 for the strongest -NAO for the first half of December since 1950. Only 2010, 2009, and 1963 were stronger than this forecast and there's a slight chance that it could reach 2010's strength. Daily NAO data since 1950: https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.nao.cdas.z500.19500101_current.csv Edit: Since 1963 and 2009 were during El Niño, 2022 is aiming to be tied for 2nd for the strongest non-Nino -NAO in the first half of December since 1950 (behind only 2010).