GaWx

Bump for @TheClimateChanger Do you have an update of Dec through the 30th? TIA I realize that with today still being colder than the avg of 12/1-30, the final Dec update will be a little colder than 12/1-30.

The model consensus is suggesting a good chance for the Jan MJO to stay inside the circle for 20+ days. Only the following Jans since 1975 were on or inside the circle for 20+ days (note that it’s been 23 years since the last one due to the MJO avg amp increasing): 1977, 1980, 1981, 1982, 1994, 1996, 2000, 2003 Of these 8 Jans in the E US, 1977, 1981, 1982, 1994, and 2003 were cold while 1996 and 2000 were NN to slightly BN. Only 1980 was AN and it was only modestly AN. That one had its MJO the furthest right of the eight Jans mainly on or inside the circle with none in phases 7, 8, or 1. Of its 31 days, 25 were in phases 4 or 5. So, none of the 8 were anywhere near a torch. Here’s the cold composite for these 8 Jans with 20+ days on or inside the circle: Here’s the composite for the other Jans near the endpoints and in between: MJO outside circle 12+ days

That is a legit concern for me, too. The forecasted -EPO/+TNH cold pattern for the central US eventually looks great for cold domination prospects for the central US, much of the Midwest, and the N NE. But the biggest risk against sustainable cold is in the SE primarily and Mid-Atlantic secondarily, where the SE ridge may be too strong if the PNA in the means doesn’t go positive. This is very difficult to forecast this far out. Although I don’t like the warmer model developments of recent days for week 2 in the E US, my hope is still that the PNA in the means will flip for Jan averaged out to match the 100% of -ENSO -PNA Decs since 1983-4 that went to a net +PNA for Jan. My other hope is that the 90 day -PNA bias of the GEFS/EPS/GEPS means that they’re currently off. The GEFS AO looks better for midmonth vs yesterday fwiw.

I’m enjoying the current cold and dry snap. I had two great walks in the Canadian air the last 2 days and expect another one today. The area got down into the high 20s for the low, not far from the 25 coldest so far. Keep in mind that as of just 10 days ago, this cold snap was nonexistent on the models! So, I consider it a bonus to enjoy.

Thanks, snowman. One of the favored analogs has been 2021-2. This was the GEFS PNA forecast 4 years ago today through Jan 14, 2022: it showed the PNA turning positive, which it did but the mean wasn’t positive enough for midmonth: To compare, here’s today’s GEFS PNA forecast, which is clearly going in the right direction at the end but still isn’t then yet a +PNA. Note the wide spread of the members, however:

Natural gas, which usually drops when the high pop. centers of the NE US and Midwest look warmer in the 2 week forecast, is down >4%. The forecasted -EPO/+TNH cold pattern for the central US eventually looks great for cold domination prospects for the central US, much of the Midwest, and the N NE. But the biggest risk against sustainable cold is in the SE primarily and Mid-Atlantic secondarily, where the SE ridge may be too strong if the PNA in the means doesn’t go positive. This is very difficult to forecast this far out. Although I don’t like the warmer model developments of recent days for week 2 in the E US, my hope is still that the PNA in the means will flip for Jan averaged out to match the 100% of -ENSO -PNA Decs since 1983-4 that went to a net +PNA for Jan. My other hope is that the 90 day -PNA bias of the GEFS/EPS/GEPS means that they’re currently off. The GEFS AO looks better for midmonth vs yesterday fwiw: Yesterday: Today:

Watch out for potential major Arctic plunges week of 1/19-26: this was released on Tue 12/30.Exclusive Weather Updates from Vaisala/X Weather & The Weather Co.Brad Harvey, senior operational meteorologist at Vaisala, says that the forecast for the 6-to 10-day period features much-above-normal temperatures from the West to Texas. Highs are forecast to reach the 50s in Denver, 60s-70s in Dallas, and 70s in Houston. The Midwest and East are forecast to be drier than normal thanks to rounds of high pressure migrating southward from Canada. The forecast is near normal for temperatures in the Upper Midwest and below normal in the East. Risks are mixed for the Upper Midwest, where our forecast takes the middle ground between the warmer GFS and colder ECMWF solutions. Meanwhile, warmer risks in the Rockies are associated with downslope flow, while the Great Basin could be colder under high pressure. The models have lacked consistency in both the 6-to 10-day and 11-to 15-day periods. “The GFS EN projects a –PNA pattern, while ECMWF trends toward a +PNA. Neither of these solutions are given higher favorability, with our forecast featuring a round of above normal temperatures in the Eastern Half and belows emerging late in the Midwest.” For more information, go to https://www.xweather.com/weatherdesk. Mickey Shuman, a senior meteorologist with The Weather Company, tells us that for most of next week, the Pacific pattern will reverse, helping to drive mild Pacific air into much of western and interior North America. However, a west-based -NAO block will impede the advancement of the mild air into the East. By the 11-to 15-day period, mild Pacific and maritime Atlantic air will overspread the entirety of Canada, essentially shutting down the risk of any major cold air intrusions, such that most of the CONUS moderates and ends up on the warmer side of normal, supporting a prolonged stretch of lower-than-normal GWHDDs. That being said, an emerging +PNA signal also suggests that there won’t be a major or sustainable warm-up and that some seasonably cold air attempts to expand south and east later in the period. The bigger story is the potential pattern change for the middle to end of the month, which could lead to noteworthy cold Arctic blasts over the eastern two-thirds centered on the week of the 19-26th. For more information, go to https://www.weathercompany.com/

I did the analysis of the 15 Jans with phase 6 during La Niña (1975-2025) Year….# phase 6 days…avg anomaly 1975…3…-8 1976…13…-9 1989…3…+8 1999…3…+2 2000…3…-4 2006…6…+3 2008…3…+8 2009…6…+1 2011…12…-7 2012…19…+1 2017…2…0 2018…3…-2 2021…8…-1 2022…4…-9 2025…2…-5 ————— 91 total days that averaged ~-2 3 MBN 3 BN 6 NN 1 AN 2 MAN BAMwx said that the phase 6 MJO/-AAM analogs had this at ~-6 to -7. So, I believe based on the above analysis that this is a good bit overdone and should be ~-2. Granted, it came in cool on average with the -2 anomaly, which to me is admittedly a bit counterintuitive. And 1975, 1976, 2011, and 2022 came in quite cold during their Jan phase 6 days showing it would be doable. But one can see that only 6 of the 15 (40%) Jans during phase 6 were in BAMwx’s cold vicinity. So, I’d still much rather it go 8-1-2. Any comments? @donsutherland1@bluewave

Thanks for clarifying for us. My bad for misunderstanding what they meant by “0-2.5% significance”. So, it sounds like they’re saying that the chance that the warmth in the E US is due to randomness is only 2.5% or lower. Do I have that right? That would make perfect sense and sort of jibes with @cny riderand my original thinking.

Actually, I think it’s the opposite because the strongest warm anomalies are in the E US though admittedly I don’t know why it shows that as “0-2.5% significance”. That doesn’t make any sense as it should be the opposite!

I love the SE brand of cold. I’ve had more than enough mild after 7 days straight of torchy and sweaty 73-80. Thank goodness a return to a long torch isn’t in the forecast. I’m hoping for mainly BN to NN with low dewpoints (sub-45 is best) til further notice! Highs of 65 or lower other than a few low 70s scattered in and lows mainly in the 30s-40s. This is best for walking.

This was released by BAMwx: Thoughts? I’m going to need to research this myself to feel comfy with BAMwx’s idea of the highly counterintuitive idea of a very cold E US on average during La Niña (-AAM) Jan phase 6 periods. They’re saying this probably because GEFS is forecasting phase 6 going into mid-Jan as per my earlier MJO forecast post. I can do the analysis but it will take time. I’m planning to look at actual temp anoms for a city like ATL, Chat., Nashville, or GSP that’s in the heart of the coldest (pink) for all phase 6 days during Jan since 1975. Actually anyone can do it but one needs lots of time to do this. In the meantime, I’ll continue to root for weak to moderate 8-1-2 over 6 or even 7. @donsutherland1@bluewave

I’m calculating that the Dec NAO will come in near -1, easily the most negative Dec since 2010. This is the first moderate to strong Dec -NAO during active Dec sunspots since 2002, when sunspots were 135. I’m estimating Dec of 2025 SSN to be 120.

Looking ahead MJOwise, I hope today’s GEFS forecast doesn’t verify as it has it going into a strengthening 6 as we approach mid Jan: Phase 6 in Jan is one of the warm E US phases along with 4-5. Say it ain’t so, GEFS! Of course, even if it verifies, the warmth is just based on the average and it can still end up cold. The EPS is better but not great as it heads into a weak 7, which is pretty neutral. I’d much prefer to see 8-1-2 for the best shot at a cold E US pattern:

Followup: The full torch period MJO is now in as I had to wait for the reporting lag. It turns out that the MJO during the heart of the torch (12/23-27) wasn’t in a typically cold track after all. Instead of a typically cold in Dec counterclockwise track of 8-1-2 of moderate to weak amp (including near or inside circle left side), it tracked clockwise weak 7-6-4-3, an unusual Dec track that one would not associate with cold as it kind of went in reverse and in typically not cold phases even though they were weak: 2025 12 23 -0.28945175 0.37228486 7 0.47157007 Gottschalk10_method:_OLR_&_ACCESS_wind 2025 12 24 -0.12800699 0.45807526 7 0.47562456 Gottschalk10_method:_OLR_&_ACCESS_wind 2025 12 25 0.16766728 0.36077648 6 0.39783412 Gottschalk10_method:_OLR_&_ACCESS_wind 2025 12 26 0.17544751 -6.13679737E-02 4 0.18587054 Gottschalk10_method:_OLR_&_ACCESS_wind 2025 12 27 4.42237742E-02 -0.35203809 3 0.35480496

One year ago today, this was the coldest Euro Weeklies map (for mid Jan): it’s always going to be hard to match something like this in the SE as a whole in the general sense. This was near the time of the first major snowstorm (that hit ATL among other places). And there was also a second very cold week around the time of the Gulf coast storm. But one doesn’t need historic periods like this to still have a great period of winter at least in more localized areas:

Today’s Euro Weeklies came in colder in mid to late Jan: 1/12-18 a week ago: 1/12-18 today 1/19-25 today:

Today’s Euro Weeklies’ SPV at 10 mb is even weaker based on mean zonal 60N winds: One week ago: Today: note Jan 12th dip to only 22 vs it being way up at 47 a week ago:

The historic January of 2025 looking better isn’t surprising as it had nearly wall to wall intense cold along with major winter storms in the SE and thus is always going to be hard to match in a general sense. The Euro Weeklies were much colder in the SE US for Jan at this point. Edit: But otherwise: 12Z ensemble means update for late week 2: good news overall for E US cold and also snow lovers: 1. GEFS H5 improved somewhat vs 0Z/6Z with a slightly higher PNA though it’s still a -PNA. The best news is that it’s significantly colder with BN temps and it’s snowier in much of the region. 2. EPS is very similar to the 0Z, which makes that good news because it’s chilly along with a nice +PNA. No caving whatsoever to the ugly 0Z/6Z GEFS.

12Z ensemble means update for late week 2: good news overall for E US cold and also snow lovers: 1. GEFS H5 improved somewhat vs 0Z/6Z with a slightly higher PNA though it’s still a -PNA. The best news is that it’s significantly colder with BN temps and it’s snowier in much of the region. 2. EPS is very similar to the 0Z, which makes that good news. No caving whatsoever to the ugly 0Z/6Z GEFS.

Thanks for your reply. I agree it is a risk, unfortunately. But my supported hopes (GEFS 2nd week on avg has been awful and much too warm) are that today’s 0Z EPS’ moderate +PNA, which starts Jan 7th, will prevail: Today’s 12Z ens runs will be extra interesting due to this major disagreement in week 2!

The 0Z EPS (another run with a transition to a +PNA and a chilly E US) and the 0Z/6Z GEFS (staying -PNA and a warm E US) are in different worlds for mid Jan. The CPC GEFS forecasts of yesterday vs today show a bad 24 hour trend if you want it cold in the E US in mid-Jan: Yesterday’s GEFS PNA forecast was heading up/nice trend vs earlier runs: Today’s 0Z GEFS said never mind, I’ll stay -PNA through the end of the run: yuck GEFS 0Z 360 hour 2m temps: mild in E US with the cold way out to the NW….yuck But the good news is that the GEFS has had a persistent -PNA and warm E US bias over the 90 day period for this map: And the EPS, a better performing and recently steadier ensemble, still has a +PNA and a chilly E US:

Carver/Met, I happen to already be knowledgeable about what BAMwx is trying to say. I don’t know why BAMwx is calling it 43 “points” gained for the GEFS. That throws off this tweet and makes it confusing. It’s actually 43 heating degree days gained for the period 12/28-1/3 vs what the run had 7 days ago (12/21 run). This means that the 12/21 run was much warmer for that period than the 12/28 run mainly because it largely was still missing the oncoming E US cold period. OTOH, the 12/21 EPS wasn’t nearly as far off because it was significantly colder than the GEFS in the E US due to already figuring it out much earlier than the GEFS. So, it only needed to gain 12 HDDs to fully see the light. The blues represent colder changes since 12/21 while the red/yellow means warmer changes.

Jax, The OHC has orange for the first time since early July:

CAD doing its magic in NC! I’m jealous of you caddies. Consider that here it is still 70.8 here (with overcast). But even this is better than high 70s with sunny 24 hours ago and better than earlier this afternoon. This contrast between GA and NC was forecasted quite well. Yesterday’s high at KSAV was a sweaty record tying 80.