GaWx

12Z model consensus is overall colder late in the runs and is just plain cold! Folks reading many posts in this thread might not realize this.

Latest bc MJO of two least inaccurate models are now very close with both into left side of circle early Jan. A good number of past instances of this sort of MJO during non-El Nino have been during cold in E US in Jan (see 7 cases below) GEFS: EPS: Past instances of left inside circle with cold E US in Jan non-El Nino: 2022 2nd half Jan: 2000 late Jan: 1999 early Jan: 1996 1st half Jan: 1994 1st half Jan: 1982 late Jan: 1976 early Jan: But this one failed to be cold: 2023 mid Jan was mild So, 7 were cold and only one wasn’t. But we may have the warm MC to contend with like for the 2023 case although the 2022 case was still cold. And we’ll have to see if the MJO really is going to verify left side inside circle/are these model progs accurate?

The multiday averaged CFS ensemble runs have been getting colder in the E US for much of early to mid Jan with a stronger +PNA/-EPO. Most recent individual CFS ensemble runs have had 2-3 weeks straight of BN temp domination in the E US. Euro Weeklies and extended GEFS from yesterday at 0Z agree. Let’s see how this evolves. Will be interesting. NG prices are at new 2024 highs. Newest run for Jan 3-9 (last 3 days of ens runs averaged): Run from one week ago for same period:

Strongest cold signal yet with NYC H5 for 1/6-12 down from 541 dm to 539 dm, which is 11 dm BN! That’s now within the 5th shade of blue vs 4th yest and 3rd on prior days. I don’t know if you folks realize how hard that is to do 2.5 weeks out for a full 7 day period on a 100 member ensemble in a warming world! The 2m temps are now the coldest in terms of how widespread they are. They’re still at the 2nd level of BN but I fully expect to start seeing the 3rd level soon assuming the strong signal continues undiminished.

Yesterday’s Euro Weeklies: Today’s Euro Weeklies: What does this change from yesterday’s run mean?

Latest MJO forecasts from the two best bc: closer together than yesterday as GEFS much closer to circle GEFS bc: EPS bc: colder potential but only if assuming MC convection doesn’t dominate as @bluewaveand my Maxar contact both warn:

The extended GEFS have on a good number of runs been suggesting 4-5 Canadian highs plunging down during ~1/3-18 thanks to a dominating W ridge/E trough. The latest 100 member Euro Weeklies mean for Jan 6-12 had a 9 dm BN H5 height at NYC (541 dm vs normal of 550 dm). IF that were to be anywhere close to verifying, that would likely allow for quite a cold week…again IF.

But if we could get most of 1/6-17 dominated by BN, there’d still be a good chance for near normal overall even if the SE ridge were strong at the end. If this were to occur after a modestly BN Dec. I’d be quite content as I never had expected Dec-Jan to average near or slightly BN.

I’d like to at least get the one cold week consistently suggested by the Euro Weeklies (EW) (Jan 6-12) for a good number of runs. And perhaps 7 or so days averaging modestly BN during ~7 days surrounding that week also sometimes suggested by the EW and extended GEFS. As long as the other 2.5 weeks aren’t too torchy, I’d be content.

Somebody in disagreement with what DT responded with this in the comments below: “Eastern based La Niña is better for cold and snow in the eastern U.S not a central based.”

DT says central Pacific La Niña is more favorable for E US cold and snow than is E Pacific La Niña. I’m confused @snowman19? Here him say this during very short portion at 5:08-5:30:

Folks, the new 0Z GEFS actually looks nice as early as Dec 30th and is the best looking that early in at least 4 days of runs. Progression is really good to see. And the 0Z EPS is a real beaut!

The 0Z 12/18 GFS ens extended looks beautiful at H5/H8 along with many Canadian surface highs dropping down during Jan 6-17. Consistent with the Euro. Bring it on!

The Euro Weeklies still look nice for cold potential Jan 6-12. H5 is a beaut for a period that’s still 2.5-3.5 weeks out!

Today’s Euro Weeklies: Jan 6-12 back to about as cold as 2-3 days ago (a strong cold signal for still being 2.5-3.5 weeks out): H5 anomalies for that week are the most negative of any run. They stick out even more prominently on the world map with the coldest now being the 4th shade of blue (vs 3rd shade on prior runs and vs only 1st shade of blue for most negative in rest of world), which gets NYC down to 9 dm BN/541 dm (vs normal of 550 dm). That’s not easy to do in a warming world for a full week on a 100 member ensemble out 2.5-3.5 weeks: If Jan 6-12 isn’t solidly cold in the E US, I’ll consider it a big bust of the Weeklies. There almost has to be some extremely cold members to achieve this cold of a mean.

End of Euro: not as pretty as prior 2

Regarding colder to start new year, EPS/GEPS agree but last few GEFS don’t, which I feel are likely largely MJO related. We’ll see which is closer to being correct regarding MJO/Pacific:

The bc GEFS and EPS MJO forecasts are on two different planets for end of Dec/Jan 1st: forecasting battle of the titan ensembles GEFS bc stalled in moderate phase 7 not far from phase 6/not favorable to cold as H5 shows: EPS bc headed into left side of circle 7/8: more favorable to cold potential E US: note that H5 is going toward restrengthening +PNA

The often highly changeable CFS ens based AAM forecast (last one from 12Z on Mon) dropped significantly vs 9 days earlier fwiw: 12/16 12Z: neutral mean by Jan 9 12/7 0Z: strong +AAM on Jan 9

End of runs (0Z): time for rate the models GFS: kind of ugly (3) Euro: decent (6) Cdn ens: pretty (7) GFS ens: still ugly (2) Euro ens: still very pretty but tiny bit less pretty than 12Z (8)

I agree this is realistic. This will include two days, Dec 26 and 27, that may flirt with record warmth for the country as a whole. But wait til just after Jan gets here though! Things could change drastically. I know. Where have we heard this before? But wx history doesn’t have to repeat itself. Don’t place any big bets one way or the other. Even my pro met contact at Maxar admitted that Jan is a tough call. I’m expecting very robust discussions and debates in here over the next few weeks. Should be fun, regardless!

18Z GEFS end: like 12Z GEFS still not pretty (actually kind of ugly) unlike beautiful EPS/CDN ens

New from BAMwx:

I agree that it is still a decent cold signal. You don’t want it that cold but I (in the SE) would love for it to be very cold.

Today’s Euro Weeklies have a slightly weaker cold signal in the E US for Jan 6-12 vs the prior 2 days though it is still a decent signal for being out at week 4. Also, the moderate cold signal for Jan 13-19 of yesterday’s run has been replaced with a neutral signal today. Also, the SPV averages a bit stronger today (not what I wanted to see). Jan 6-12: not as strong of a cold signal