GaWx

You’re looking at Phil only though. 1/2018 was significantly colder S and W of you.

They keep getting colder. The bulk of the SE US being 8-12 F BN for 1/6-12 is easily the coldest Euro Weekly map I can recall for the SE US still over a week out and probably ever for any one week. Also, the weeks surrounding that week are cold, especially the week after with even it having many areas 7-10 BN! This run suggests a 5 to 7 BN Jan would be quite possible in most of the SE US similar to 2018, 2011, 1985, 1904, and 1887 Niñas. 1996/1984 Nina’s were not as cold and only 1918/1893 were even colder. So, this run implies a chance for the SE to have a top 3-7 cold Jan for La Niña out of ~40!

I keep saying this but it’s because they keep getting colder. This image below for 1/6-12 with the bulk of the E 1/3 of the US 8-13F BN (4th shade went from just tiny bit over W VA to much larger area several hundred miles either side of line from near Chicago to ATL as well as Richmond to Savannah and nearby areas) is easily the coldest Euro W map I can recall for the E US still over a week out and probably ever: Also, 1/13-18 is the coldest by far for it with most of the E US in the 3rd shade. This run suggests a 5 to 7 BN Jan would be quite possible in a decent portion of the NE and SE US similar to 2018, 2011, 1985, 1904, and 1887 Niñas. 1996/1984 Nina’s were not as cold and 1918/1893 were even colder.

The 0Z EPS has a whopping 21 (42%) of members with a T+ of wintry precip in FL! The entire SE is covered with about the highest mean yet:

I’m surprised @snowman19hasnt posted about the suddenly much more active sun! Chances for a major SSW in late Jan through Mar are high per Joe D’Aleo’s report, which showed a significant correlation between active solar/W QBO and major SSW chances. 2024 12 01 2024.917 119 17.1 25 30 2024 12 02 2024.919 132 19.8 19 22 2024 12 03 2024.922 125 13.3 20 24 2024 12 04 2024.925 125 15.8 14 16 2024 12 05 2024.928 129 9.8 12 16 2024 12 06 2024.930 117 23.9 18 22 2024 12 07 2024.933 136 17.4 15 18 2024 12 08 2024.936 146 28.5 12 15 2024 12 09 2024.939 115 11.0 10 12 2024 12 10 2024.941 149 17.5 7 9 2024 12 11 2024.944 124 12.4 9 11 2024 12 12 2024.947 115 6.6 11 13 2024 12 13 2024.949 112 16.7 12 13 2024 12 14 2024.952 97 18.3 13 15 2024 12 15 2024.955 109 11.9 12 14 2024 12 16 2024.958 100 9.9 13 16 2024 12 17 2024.960 92 13.2 16 19 2024 12 18 2024.963 116 6.8 17 19 2024 12 19 2024.966 128 15.3 15 17 2024 12 20 2024.969 155 15.9 26 29 2024 12 21 2024.971 162 16.7 14 16 2024 12 22 2024.974 193 26.6 13 15 2024 12 23 2024.977 224 32.9 12 14 2024 12 24 2024.980 216 44.5 9 9 2024 12 25 2024.982 239 24.1 11 12 2024 12 26 2024.985 267 32.5 9 11 2024 12 27 2024.988 257 23.0 10 13

The above posted NOAA weekly week 3/4 outlook had been until today the coldest week 3/4 outlook on record (back to 2015) for the SE in Jan. Now it has been replaced by today’s as it actually has a stronger signal in FL, much of GA, SC, NC, and VA as those areas are all further into the 3rd shading: Precip signal is neutral to weak wet in all of SE (nearly 2” or more qpf) which would be quite wet compared to most very cold periods:

New Euro Weekly 2m temps for Jan 6-12 (see image below) is by a good margin the coldest yet and is the coldest Euro Weeklies map covering a 7 day period and still over a week out I can ever recall seeing for the E US: the 3rd shading of blue is 3-6 C/5.4-10.8F BN, which covers just about everywhere in and near the E including 200-300 miles offshore the E coast. That means the bulk of the E US is 7-10 BN! There’s even a tiny area of 3rd shade (-5.5F) in Cuba! The coldest is in W VA, where for the first time a tiny bit of the 4th shade is showing (~11F BN)! This map is easily the coldest on the entire globe for that week and beyond. Also, the subsequent week is cold. Here’s Jan 6-12:

New Euro Weekly 2m temps for Jan 6-12 (see image below) is by a good margin the coldest yet and is the coldest Euro Weeklies map covering a 7 day period and still over a week out I can ever recall seeing for the SE: the 3rd shading of blue is 3-6 C/5.4-10.8F BN, which covers everywhere in and near the SE including 200-250 miles offshore along the SE coast. The bulk of the SE is 7-9 BN! There’s even a tiny spot of 3rd shade in Cuba (~5.5 F BN)! That’s very hard to accomplish. The coldest is in W VA, where for the first time a tiny bit of the 4th shade is showing (~11F BN)! This map is easily the coldest on the entire globe for that week and beyond. Also, the subsequent week is cold. 1/6-12 Precip map is wettest for that period, yet (NN to AN everywhere)! It shows Miller A potential. That equates to ~1-1.25” in most areas, a lot of qpf for such a cold period since they’re often dry:

A quick look at all 3 12Z ensemble run members continues to show a decent % with wintry precip (flurries/T or more) in FL. I counted on the EPS 15 of 50 (30%) in FL! On the relatively conservative EPS this far out (7 days+) that is very notable and gets me excited for a shot at least flurries here. Haven’t had even a T of any kind of wintry here in 7 years.

All 3 12Z ensemble means are very cold in the SE late. It’s almost a certainty that an overall cold first half of Jan is on the way for the SE with the coldest first half by far since 2018 (all others since NN to AN). It will very likely end up colder in the SE overall than 2014 and 2015, which weren’t that cold in the deep SE. So, it looks likely that the first halves of Jan in 2011, 2018, and 2025 will be the coldest 3 of the last 15 for the SE overall, all 3 being La Niña. Both 2011 and 2018 had one major winter storm in the first half of Jan affecting parts of the SE: -1/9-10/11 was big in much of the well inland SE including Atlanta, where it had a very large impact and lead to closings much of that week -1/3/18 historic SE coastal winter storm A notable winter event or two is likely in the first half of Jan 2025. How notable and where nobody knows.

The updated bc GEFS/EPS are still looking favorable for cold (it’s hard to be in a better position than these weak left sided tracks): Yesterday’s extended bc EPS *fwiw* suggests no strong MC anytime in Jan:

That would make 2024-5 a significantly stronger La Niña than 2008-9 on a relative basis to surrounding tropical waters’ anomalies considering that RONI and ONI were very close in 2008-9 vs 0.5 to 0.6 apart now.

If this daily RONI chart is pretty accurate, OND RONI would end up near or slightly cooler than -1.0. That would already give 2024-5 a borderline moderate/weak La Niña peak at the very least on a relative to surrounding global tropical waters basis. My guess for official OND RONI is at least down to -0.95. When combined with other factors including the SOI, I consider that we’re in moderate La Niña for all practical purposes although not officially (not ONI-wise).

The 0Z EPS mean is much colder than the 12Z and is the coldest of any yet. For example, much of the Carolinas are ~9F BN over the 9 days Jan 2-10! That long of a period is categorized unofficially as cold for an ensemble mean. The E US easily has the coldest anomalies of anywhere on the globe for Jan 2-10 overall! Thus, I’ll be surprised if tomorrow’s weeklies aren’t the coldest yet for the week of 1/6–12. The southern extent of the measurable snow mean is about the furthest south yet of any EPS run with it reaching much of the Gulf/SE coasts keeping in mind that the EPS is the most conservative of the 3 major ensembles: The typically more liberal GEFS (0Z) has the measurable down to @pcbjr’s abode in Hogtown! This is about as far south as I can recall even the GEFS mean ever going in the FL peninsula:

1. Thanks. But operationals are almost always jumpy at 240+. So, I put little importance on operationals days 10+, when I prefer ensemble means. 2. So, looking at 12Z Euro/GFS/CMC ens means, the trof is ~80W/near our longitude. 3. Would it be too dry for the SE to get a synoptic scale winter storm with the mean trof near 80W? I’d say yes in many cases, especially when there’s just the N stream keeping it dry. I’d then prefer it be ~90W. However, an often hard to prog (more than a few days out on models) short-wave induced split flow underneath the N stream would be a way to make it moist while the N stream to the north keeps the cold air in place at the sfc. 4. Here are 9 examples of moist split flow just in advance of SE winter storms even with the N trof even further east in all but one case: 12/8/18: (El Niño) N trof 72W but WSW flow SE 12/8/17: (La Nina) N trof 85W but SW flow SE 1/21/16: (El Niño) N trof 70W but WSW flow SE 2/25/15: (El Niño) N trof 77W but WSW flow SE 1/9/11: (La Nina) N trof 70W but incoming SW flow underneath 2/11/10: (El Niño) N trof 65W but incoming WSW to SW flow underneath 1/29/10: (El Niño) N trof 70W but incoming SW flow underneath 2/25/04: (warm neutral) N trof 70W but SW flow SE 1/9/04: (warm neutral) N trof 60W but WSW flow SE 5. Could there be a shortwave induced moist split flow underneath the progged 10-15+ day +PNA induced cold mean E trof coming that can’t yet be seen on ens H5 means? It’s very possible. Would I bet on it? No because we’re in La Nina, when it is more difficult to get a split flow. If this were El Niño with a frequent moist S stream, I’d be more excited. Regardless, sometimes these occur during La Nina like in 2 cases posted above, 12/8/17 and 1/9/11. Also, the progged couple of week long cold dominated period as opposed to just one and done helps. Plus there are obviously other ways to get a winter storm. So, keep hope alive, folks!

Are you talking about the Euro operational trough or the Euro ensemble mean trough? Also, what forecast days/hours are you referring to?

Despite the recent at or near record rapid strengthening of La Niña from Nov to Dec, Jan is likely going to be another BN temps month in much of the E US. If so and with 2 of the 3 winter months BN, this winter would highly likely not be the AN E US winter (+2+ F) many including both of us expected. In that case Feb would have to be an absolute blowtorch just for the slight chance for DJF to average +2+.

This is about the coldest 12 run CFS ens map I can recall ever seeing for the SE for a full week not starting for 2 weeks meaning a very strong cold signal for the start of the period being 2 weeks out: this has 5-6F BN over almost all of the SE! Remember that this is 12 runs of a 4 member ensemble and is actually likely underdone, if anything, due to smoothing. Precip averages 0.25” BN, which for such a cold period is actually decent since strong cold is more often than not dry. That would still be 0.5-1” of qpf for most.

A split flow (more frequent in El Niño) is often the best bet to get significant wintry precip for much of the SE, including the deep SE (see image below for a deep SE modeled example): -Having the N stream to the north of one’s latitude with the trough axis nearby or to the east (it’s actually well to the east in the image below) allows for ample supply of cold at low levels -Having the S stream near or a little south of one’s latitude with its trough axis to the west allows for moist WSW or SW flow bringing the Gulf moisture/warmth above the low level cold A textbook modeled split flow: note the N stream with cold WNW flow well to the north (trough axis to the east) while at same time there’s S stream with moist WSW flow nearby bringing in ample moisture (trough axis to the west). The precip map for this showed snow on the northern fringes in the deep SE: Edit: These are not easy to achieve as one could imagine (delicate setup), probably moreso when not in El Niño. These are often not going to be seen on ensemble means out more than a few days and they often appear for only a short period.

When I start counting more than just a couple of ensemble members with wintry precip in FL (anywhere from T to measurable), it starts to get my attention for especially us deep SE folks where it is pretty rare. I haven’t had even just a T of any kind of wintry precip in nearly 7 years, the longest for this area at least going back 140 years! The latest runs of 2 of the 3 major ensembles all have the largest # of members like that yet this season (not surprising considering how cold they are and the strong hint of multiple cold plunges as opposed to just one and done). -18Z GEFS: 11 of 30 (37%) have it in FL! Prior 3 runs had 5 each. This usually has highest of the 3 ens but 37% is still very impressive! -12Z GEPS: 4 of 20 (20%); 0Z had only 1 and yesterday’s 12Z had none -12Z EPS: 4 of 50 (8%) but 0Z had 7 of 50 (14%); this usually has lowest of the 3 ens. -The bulk of the wintry events are near the end (Jan 8-10) but a couple on the GEPS are as early as Jan 4. @pcbjr

The latest model consensus covering much of the 1st half of Jan suggests a good chance for a +PNA (trended recently from neutral or -PNA), -AO, and -NAO. (The 2nd half of the month, which only the extended ensembles show, is still too far out for reliability.) During non-El Nino DJF back to 1950, these are the 15 non-Nino months with a +PNA (+0.25+), AO (-0.5-), and -NAO (-0.25-) along with E US temps: -2/2013 (weak +PNA/-NAO; +EPO): cool SE/MidATL, NN NE -1/2011: cold -12/2005: cold -1/2004 (weak +PNA/-NAO but -EPO): cold -12/2001 (+EPO): mild -12/2000: cold -12/1995: cold -12/1989: cold -1/1985: cold -2/1968: cold -2/1963: cold -1/1963: cool -1/1960: mild -1/1955 (+EPO): cool -12/1952 (+EPO): cool SE/mild NE So, 11 of these 15 were cold or cool most everywhere. The other 4: -2/2013: +PNA and -NAO weak and +EPO -12/2001: +EPO -1/1960: can’t explain -12/1952: +EPO So, if we end up with the full Jan averaging +PNA/-AO/-NAO and considering the favorable MJO for at least the 1st half, the odds would be high that the only index standing in the way of a cool to cold E US Jan would be a +EPO. Current consensus has it mainly negative to neutral much of first half of Jan.

12Z ensembles are still cold dominated in the E US day 9+: - 12Z GEFS is colder than 6Z, which was overall slightly warmer (by 4 HDD) than the then coldest run to date 0Z and looks to be back at least about as cold as 0Z. Did it gain at least the full 4 HDD back? I’m guessing yes, which would mean at least tied for coldest run yet. - 12Z EPS looks colder than 0Z, which was overall a bit warmer than yesterday’s 12Z, which had been the coldest run to date. The 0Z was 6 HDD warmer than yesterday’s 12Z. But today’s 12Z EPS may be back to at least as yesterday’s 12Z. If so, it is at least tied for coldest run yet. I’ve said this before and feel it deserves to be repeated for readers who don’t come here often and thus who may be confused. Based on some of the posts ITT, a reader not too familiar might not realize the cold potential in the E US for at least much of the 1st half of Jan. The potential is very real and is not baseless hype, which I actually hate. Model consensus has been insisting on this being likely. It will of course warm back up eventually. That’s obvious. But well before that we have the strong cold potential. It looks like the most intense cold would likely come in at least two waves meaning warming in between of course.

PNA update: 1. The PNA after applying a rough 1.8 tabular conversion factor is roughly +1.8 MTD. It will be dropping for the rest of Dec as has been well predicted by GEFS means since the Dec 14th run. But I maintain that won’t be enough to prevent 2024 from having a decent shot at the record high Dec +PNA for non-El Nino, which is currently 2020’s +1.58. My current projection is for ~+1.45 to +1.70. So, it will probably be pretty close. The 2nd highest for non-Nino is 1960’s +1.46. So, I still think there’s a very good chance that 2024 will exceed the current 2nd highest and end up either highest or 2nd highest for non-Nino Dec PNA. (Records go back to 1950.) The reason I’ve been posting a lot about the strong Dec +PNA projection is that there’s a significant tendency for a strong non-Nino Dec PNA to carryover to Jan. As posted previously, the average Jan PNA for the non-Nino winters with the strongest 5 Dec PNAs on record has averaged +0.9 with 3 of the 5 Jans strong (within top 9 for non-Nino Jan): +1.51 (2001), +1.41 (1981), and +0.97 (1986). The other two were either weak +PNA (2006’s +0.43) or neutral (2021’s +0.19). 2. Even more significantly when looking ahead to Jan, especially with a strong -AO and moderate -NAO being predicted as well as a favorable for cold MJO, is to note that today’s 0Z GEFS based PNA prog for the 1st week of Jan has risen notably (see images below) and easily has the highest of the last 6 runs going into Jan as the 0Z GEFS maps showed a significant shift toward recent EPS runs: Here’s yesterday’s to compare to: Tabular monthly PNA since 1950: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.pna.monthly.b5001.current.ascii.table

MJO forecasts: pretty consistent with the often favorable for cold E US with still having weak left side

Merry Christmas and also Happy Hanukkah as it starts later today. 0Z ensembles: 1. Whereas EPS retains a very cold look at 500 mb at the end and is still cold overall especially at the end, the total HDDs of the run dropped some vs the 12Z. Thus, today’s Weekly for 1/6-12 may not be as cold. 2. Bigger news: Last 2 runs of GEFS have gone a long way toward the EPS. HDDs are up significantly. The end of the 0Z GEFS is even colder than the 0Z EPS or even the 12Z EPS. The end is the coldest GEFS run yet vs the extended portions, which go out further at 0Z, of prior 0Z runs. The very cold end has MB 850s covering almost all of the E 1/2 of the US: