GaWx

Why not? Other long range models run daily like GEFS. Long range should always be taken with a grain, regardless, due to high levels of forecast uncertainty. But why not run them daily since despite unreliability they can at least hint at potential trend changes past 2 weeks. The EW have been halfway decent imho. For one thing, they had very early hints about the upcoming very weak SPV. For another, they’ve done pretty well with hints about general levels of Atlantic tropical activity weeks out.

Today’s Euro Weekly 2m temp anomalies vs yesterday’s run: Dec 1-7: ~same Dec 8-14: similar for most/slightly stronger cold in Lakes region Dec 15-21: similar for most/slightly colder NNE Dec 22-28: similar for most/slightly colder NE/slightly less cold Lakes region:

Today’s Euro Weeklies 10 mb 60N mean zonal wind isn’t as weak as recent runs: Today’s run (11/19): Yesterday’s (11/18): Does anyone else see what I’m referring to? I’m not just talking about whether it actually reverses. I’m talking more about the period afterward.

This is a good post imho and mirrors my general thinking:

12Z ensemble means at H5 just after the cold shot at the end of Nov: GEFS: EPS: more amplified including much stronger SE ridge than GEFS: We’ll see which verifies more closely. Lately, cold has had the edge.

Thanks Don, I see your point about the unpredictability of upcoming NE snow. Moreover, this thread isn’t strictly about NE snow (as you know). It’s of course also about NE and other areas’ temperatures, wintry precip in other areas, and many other things. Wintry precip, which is usually more variable/localized than the cold influence of Arctic airmasses, is thus often less predictable than temperatures. Therefore, regarding the potential lagged effects of an SSWE, I’m guessing that temperatures in the NE US as well as for other areas for whatever period would be less unpredictable than snowfall. From what I’ve learned, there’s a significantly better chance than normal for a multi week long period of cold domination in the E US usually starting 2-3+ weeks after an SSW. More often than not the cold will appear in the E US. Most likely that would naturally mean increased wintry precip in parts of the E US, but where is the question? Especially if there’s a decent sized sample, I do like to look back at specific cities’ stats (temps and wintry precip) to give me some idea of the potential, regardless.

Natural gas is up 4.5% on colder model trends.

AAM forecast (CFS ensemble): big change for mid Dec vs forecast from two days earlier (warning: these are highly volatile on right side of graph): 11/18/25 AAM forecast: suggests it may go + (El Ninoish) in mid-Dec?!? 11/16/25 AAM forecast: 11/11/25 AAM forecast: @snowman19

More stuff related to weak to moderate Dec phase 8 having been the coldest Dec phase 8 MJO on average: Dec 9-18 of 1989 was frigid/~tied for the coldest Dec phase 8 in the E US since 1974 along with 5.5” of snow at Baltimore (2 events) and it was weak/near the circle and slow moving: also note that it stayed frigid through this very weak phase 1 and the moderate phase 2: About tied with the frigid 1989 was the very cold 12/6-9/2002. Note that this phase 8 wasn’t too far outside of the circle (moderate phase 8): Temperatures are based on Baltimore as an E US proxy.

IF the 11/18 bc version of the extended EPS were to be right, you couldn’t ask for a better position of the MJO in Dec/Jan: just outside the circle in phase 8 (and very slow moving making it last longer would be a big bonus) is about the coldest on average in the E US as it’s colder than strong phase 8 on average (though there’s always lots of variation of course): if you asked me to place it in a better place and speed of movement in Dec or Jan I couldn’t:

Latest (yesterday’s) Euro Weeklies for 12/1-7 fwiw shows it warmer than normal in much more than FL though we’ll see whether this cools off today considering the colder end of Nov (lots of model volatility currently):

Today’s 2 week GEFS MJO progressed significantly more quickly vs yesterday’s run into phase 7! Today’s 2 week GEFS (11/19) is 2 days faster making it into phase 7 vs yesterday’s run and is already halfway through phase 7 as of 12/3! Yesterday’s 2 week GEFS (11/18) didn’t get to phase 7 til 12/1 vs today’s 11/29: Yesterday’s extended GEFS (11/18) didn’t have it halfway through phase 7 til 12/7 meaning today’s 2 week GEFS gets to halfway through phase 7 four days faster (12/3) than yesterday’s extended GEFS (not til 12/7)!

How much snow did Baltimore get during the 13 phase 7 Dec periods that were during La Niña? I’ll check now: 12/16-19/1974 (temps 1 AN): 0.4” 12/7-9/1988 (temps 1 BN): 0.8” 12/23-25/1988 (temps 5 AN): none 12/9-19/1995 (temps 7 BN): 1.5” (3 snows) 12/20-23/1998 (temps 4 AN): 3.0” on 12/23, which was very cold 12/20-30/1999 (temps 3 BN): 0.2” 12/11-14/2000 (temps 5 BN): T 12/14-21/2008 (temps 2 AN): T 12/16-20/2010 (temps 11 BN): 1.2” 12/9-11/2017 (temps 5 BN): 2.8” 12/17-20/2017 (temps 5 AN): none 12/19-31/2021 (temps 7 AN): T 12/28-31/2024 (temps 13 AN): none ———- From this list: -Temps averaged right at normal -9.9” snow over 77 days or on avg 0.13”/day How does 0.13” snow per day of phase 7 in Dec La Niña compare to all of 1974-2025 Dec climo at Baltimore? They averaged 2.2”/Dec 1974-2025 or 0.07”/day. Compare the 0.13”/day to 0.07”/day: that’s 185% of the average for all Dec days since 1974 and the conclusion is that Baltimore did quite well overall with snow during phase 7 in Dec for La Niña vs the avg for all Dec days. @stadiumwave

I’d call it average. At Baltimore since 1974 during 3+ day long phase 7 periods during Dec (32 of them adding to 185 days), they’ve averaged 0.5 F warmer than normal with the coolest tending to be somewhat weak and warmest tending to be somewhat strong though with much variation. The range during La Niña has been as cold as 11 BN (12/16-20/2010), 7 BN (12/9-10/1995), and 5 BN (12/9-11/2017) to as warm as 13 AN (12/28-31/2024) and 7 AN (12/19-31/2021). Breakdown of these 13 phase 7 periods during La Niña in Dec: 1 MB, 4 B, 2 N, 5A, 1 MA

That’s pretty amazing considering that Brooksville, FL, got down to an incredible 27 on Nov 12th!! Here’s where Brooksville is located, well on down into C FL! To be fair though, elevations are 100-180 feet, quite high for FL.

Today’s Euro Weeklies 2m temp anomalies vs prior run in E US Dec 1-7: slightly cooler NE US but still mild overall Mid-Atlantic and especially SE/warmest week of Dec Dec 8-14: NE cooled slightly from slightly AN to NN but SE ~same Dec 15-21: slightly warmer SE (was NN); ~same NE Dec22-28: slightly warmer but still coldest week of Dec

~Dec 14-16th is my hope for a change to cold domination in most of the E US based on the MJO being progged to then get into 8 and allowing ~2.5 weeks following an SSWE to start a cold dominated pattern in the E US. In the meantime, the weekend after Thanksgiving giving has cooled a lot and looks a bit chilly as of now vs having looked mild just 3 days ago.

This only recently seen on the models cold shot is for the weekend after Thanksgiving. So, this is technically during the last days of Nov. Then I still expect a mainly mild first half of Dec. while the MJO crosses 7 and we wait to see what the SSWE does just afterward. Of course expectations and reality sometimes don’t match well.

That’s quite the cooldown! The EPS has also cooled down over the last 48 hours of runs for the weekend after Thanksgiving though not to as cold as GEFS.

MJO model progs: -11/18 GEFS/EPS runs similar to yesterday day by day along with good progression into 7(GEFS) and well into 7 (EPS). -11/17 extended EPS remains consistent with recent runs with it getting into 8 on 12/14. But the big news is that the extended GEFS is its most progressive yet and with it actually moving into 8 a day earlier than the EPS (12/13). At RDU/BWI since 1974 for the 23 three+ day long Dec phase 8 periods averaged out: lots of variation but with solid tendencies -78%/61% of Dec phase 8 were cold -Compare that to only 22%/13% that were mild -Phase 8’s three+ day long periods have averaged 5 days with the longest being 13 days -Phases 1 and 2 have also averaged cold at BWI but with again lots of variation but with solid tendencies Based on all of this as well as a typical couple of weeks+ lag of cold in the E US after an SSWE, I’m hoping for E US cold domination to start around Dec 15th. Until then, I expect mild to dominate much of the E US, especially mid-Atlantic south. 11/17 GEFS extended: 11/17 EPS extended:

To me, NYC has a very snowy climate. Then again, my avg annual snow is only 0.2” with most winters getting none. My area hasn’t received a foot+ of snow for an entire season since 1800. I’ve also lived in Atlanta, where their avg is still “only” 2”. So, when I see a city’s average at 20”+, ten+ times as much as ATL and 100+ times as much as SAV, that there is very snowy! Atlanta’s never even gotten close to 20” in a season! Aside: Cloudflare problems had been causing widespread outages this morning, including here.

From JB today: Euro MJO closest analogs 1983 and 1989 The severe cold Decembers of 1983 and 1989 both raise the spectre of a cold shot letting loose into the Texas Citrus areas, with Fla secondary concern had a major stratwarm in mid to late November, almost identical to now —————- The only problem with this is that there was no major stratwarm in mid to late Nov of 1983 or 1989 or anytime during early to mid winter for both for that matter: https://www.researchgate.net/figure/The-SSW-and-SFW-event-onset-date-year-and-type-identified-in-the-NCEP-NCAR-dataset-The_tbl1_267063738 ———- Also, I checked to see if the 60-90N temperatures in the strat. in mid to late Nov were notably warm and they weren’t. Lastly, I checked the zonal winds at 60N in both Novs to see if they were weak despite no actual reversal. They weren’t as they were pretty close to normal. https://acd-ext.gsfc.nasa.gov/Data_services/met/ann_data.html#ncep_clim_stats_nh

This is by a good margin the weakest SPV on any run. If this verifies closely, this would be the weakest late Nov to early Dec SPV by a good margin since way back in 1987! We know that one month later there was a historic SE winter storm, which gave Atlanta 4” of sleet, very heavy snowfall in some other areas, and ZR down all of the way down here.

Per this EW run’s weekly 2m maps directly from the source, it remains a step down process from a mild E US start: Dec 1-7: mild Dec 8-14: cools some to slightly mild to normal Dec 15-21: cools to normal Dec 22-28: cold comes in around Christmas!