GaWx

To add: -1983 doesn’t fit -1985 strong 2nd half of Oct -1989 was fairly stout last 1/3 of Oct -2000 wasn’t strong but was stronger than avg

The 6 coldest La Niña to neutral ENSO Decembers in the E US as a whole since 1974 have been 1983, 1985, 1989, 2000, 2005, and 2010: Here are the respective Dec MJOs: 1983: mainly inside COD or just outside/no strong 1985: almost all inside COD 1989: most of 8/1 just outside COD or inside it/no strong 2000:almost all just outside or inside COD 2005: all inside COD 2010: all just outside or in COD What do these 6 have in common regarding the MJO? No strong and most days just outside to inside COD. Below are the extended progs that have the Dec 1-21 MJO: look how strong they are, especially GEFS but even the Euro is solid compared to the six cold Decembers posted. My concern is that the MJO amplitude will be too strong, based on history, to allow for a widespread intense cold dominated E US in Dec. Thus, I’m hoping the progs remain going into 8, but weaken. My hypothesis as to why strong MJO has had a tendency (though not always, of course) to not be as cold as weaker MJO is because the higher amp may tend to bring up too much warmth from the tropics, where the MJO is measured: Any opinions?

Domination in the SE by mild/SE ridge in the first half of Dec has been forecasted by the Euro Weeklies for over a week. They’ve been steady as a rock. I’d be very surprised if it isn’t mild in the means. After that it is up in the air though recent runs have been suggesting a weaker version of a SE ridge/slightly warmer than normal for 12/15-21 has been suggested for the SE.

There hasn’t even been one 3+ day long Dec MJO phase 8 since 2017 and the one before that was way back in 2009! So, if the models are right with their 3++ day long phase 8, it would the first time in 8 years and only the 2nd time in 15 years! A whopping nearly 80% of 3+ day long Dec phase 8 periods averaged colder than normal at Raleigh though with lots of variation. When amplitude is <1.5, that rises even further to 85% along with an average of 5.0 F BN. If it’s a pretty strong amplitude (1.5+), it actually averaged only 0.5 F BN at Raleigh. At Baltimore, it’s pretty similar for Dec phase 8 with 4.8 F BN for amp <1.5 but only 0.3 F BN for amp >1.5. Fortunately, most Dec phase 8 are <1.5 amp.

Today’s Euro Weeklies 10 mb zonal wind mean is slightly weaker early and allows most to reverse unlike yesterday. However, afterwards it looks like yesterday’s significantly stronger run: Today’s: Yesterday’s: Two days ago: significantly weaker

Thanks, Don. One thing helping 2025 vs 1983 is that 1983 didn’t have a weak SPV as it didn’t get <25 m/s through Nov and Dec:

Today’s GEFS gets to phase 7 a day earlier than yesterday’s (11/28 vs 11/29) and three days earlier than the run from 2 days ago. The 11/19/25 Euro-ext gets it to phase 8 ten days earlier (12/5) than the prior run (12/15): Prior run (11/18/25):

Based on H5 height comparisons (not H5 height anomaly comparisons), I strongly doubt that H5 temps on 11/11/2025 were as cold as those of 11/26/1950: 11/26/1950 0Z: N NC ~520 dm per upper right map 11/11/2025 6Z: N NC 528 dm However, in terms of H5 temperature anomalies for any date in Nov back to 1950, I feel it’s likely because NC H5 ht anomalies on 11/11/2025 were as low as -45 dm vs 11/26/1950’s lowest being ~-41 to -42 dm per the comparisons of these two maps. Had the 11/11/2025 pattern instead occurred 2 weeks later, I believe it likely would have broken the Nov H5 temp. record. Keep in mind that H5 heights are directly related to air temps from H5 down to the surface.

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.