GaWx

So, these 11 very cold RDU weeks since 2011-2 averaged an impressive 2.7” of snow and/or sleet. But the median is much lower, 0.9”. Thus, if I were living there, I’d certainly consider 2” during Jan 6-12 a solid win and 4” a big win. And having 3 of 11 with 6-9” (at or above avg season total) tells me that getting a full season’s worth then due to the degree of cold is not at all out of the realm of reasonable possibilities, especially if the bulk of the wintry falls as snow. Possibly a 25% chance? Of course any is a win in my book. Also, these stats show that getting a significant portion of the wintry as ZR is quite possible (maybe 25-33% chance). So, it is mean/median SN/P 2.7”/0.9” plus possibly some amount of ZR.

More regarding the frigid Jan 6-12 on the Weeklies. As has been said, it isn’t projected to be dry like very cold weeks can be. As has been shown for several days, the signal is mainly neutral to slightly wet. Today’s is slightly wetter than yesterday’s/others and this continues to show good chances for Gulf Miller A potential as many members and operationals have shown. Most are 0.8-1.1” qpf. RDU is at 0.8” qpf for Jan 6-12 along with 13 BN: RDU coldest 7 day periods (-10 BN or colder) since the winter of 2011-2 show this would be the coldest week since Jan 1-7 of 2018. In terms of absolutes as opposed to anomalies, 1/6-12/25 is being forecasted by today’s Euro Weeklies to be the 3rd coldest 7 day period at RDU since the winter of 2011-12 with only Jan 1-7, 2018, and Feb 15-21, 2015, colder. RDU 7 day period temp. anom: rainfall/wintry 12/20-26/22 -11: 1.22” rainfall/T wintry 12/6-12/18 -11: 2.48” rainfall/8.9” SN 1/14-20/18 -11: 0.49” rainfall/6.1” SN 1/1-7/18 -21: 0.06” rainfall/0.9” SN 2/9-15/16 -15: 0.33” rainfall/0.2” wintry 1/17-23/16 -12: 1.19” rainfall/1.2” mix +icestorm 2/15-21/15 -22: 0.67” rainfall/1.4” mix 2/23-3/1/15 -15: 1.87” rainfall/6.5” mix 2/11-17/14 -10: 1.30” rainfall/3.7” mix 1/20-6/14 -10: 0.50” rainfall/0.1” wintry 1/22-28/13 -10: 0.33” rainfall/0.2” mix So, all 11 of these periods had wintry precip with all but one having measurable. The heaviest snowfalls tended to be with over 1” of rainfall though the 3rd heaviest snow (1/24-20/18) had only 0.49” of liquid equiv. So, I’d say that 0.8” of liquid equivalent would be pretty favorable for significant wintry precip.

Ditto to the above with today’s Euro Weeklies ens mean once again coldest by a decent margin for the SE US so far for Jan 6-12 and coldest for the SE US a week+ out I can recall for any week since I’ve been following this product (several years). The bulk of the SE US active posters are ~11-13 BN. The coldest days are 1/10-11 when many are nearly 20F BN, a very strong signal from a large ensemble still 12-13 days out! Don’t be surprised if we end up with 1-2 days that are nearly 25F BN! Note that the area covered by the 4th shade (-11F or colder) is even larger today. We could easily not have another week like this in the SE US for many years to come. Credit to the Euro Weeklies starting to see a cold signal for Jan 6-12 two weeks ago! It still looks solidly cold for Jan 13-18 though not at least yet close to this degree.

Ditto to the above with today’s Euro Weeklies ens mean once again coldest by a decent margin for the E US so far for Jan 6-12 and coldest for the E US a week+ out I can recall for any week since I’ve been following this product (several years). The bulk of the E 1/3 of the US is 9-13F BN. The coldest is near Nashville with 15F BN! Note that the area covered by the 4th shade (-11F or colder) is even larger. We could easily not have another week like this in the E US for many years to come: Credit to the Euro Weeklies starting to see a cold signal for Jan 6-12 two weeks ago!

The last 2 EPS runs have each had 15 (30%) of its members with at least a T of wintry precip here, something we haven’t had in 7 years (longest drought at least since 1880s). The 0Z EPS mean has us way up at 0.6” from those 15 members! That means that run’s mean is at 3 times our average annual snow in just the next 2 weeks. I haven’t seen model predictions like this since the big 1/3/18 coastal winter storm. The next run probably won’t have as much. So enjoy it while it is there. @gtg947h @Awesomesauce81

Per the model consensus, especially today’s GEFS, there’s a good chance for the following to verify when averaged out over Jan 1-11: PNA > +0.5 AO < -2 NAO < -0.5 -EPO Since 1950 the only Jan 1-11 with this combo were 2010 and 1985 (the only La Niña). So, this would be a rare occurrence if it occurs. On top of that the MJO is forecasted to be favorable for a cold E US.

Per the model consensus, especially today’s GEFS, there’s a good chance for the following to verify when averaged out over Jan 1-11: PNA > +0.5 AO < -2 NAO < -0.5 -EPO Since 1950 the only Jan 1-11 with this combo were 2010 and 1985 (the only La Niña). So, this would be a rare occurrence if it occurs. On top of that the MJO is forecasted to be favorable for a cold E US.

12Z EPS: a whopping 30 of 50 (60%) have at least a T of wintry precip somewhere in FL (largest % I can recall seeing over the years on EPS this far (a week+) out) with 13 of those giving TLH a T+! 18Z GEFS: 14 of 30 FL!

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+.