GaWx

1 hour ago, donsutherland1 said:

Yesterday, I noted that the GEFS was trying to push an EPO+, but its forecast 500 mb pattern was profoundly different from any of the December WPO-/EPO+/AO-/PNA- clusters. That suggested that either the teleconnection idea was off or the pattern was off, rather than some novel outcome. 

Overnight and through today's 6z cycle, the GEFS has continued to evolve. It has added a WPO+ to its EPO+ idea and restored its earlier idea of a AO+. It has now joined the Canadian ensembles that keep the MJO out of Phase 8 through its forecast horizon. In short, its previously significant areas of "disconnect" have disappeared overnight. Its forecast pattern is now more consistent with what one would expect.  For now, the GEFS is trying to build a credible milder alternative scenario for the pattern/temperature evolution in North America toward mid-December. 

The EPS has not shifted toward that emerging GEFS idea. Therefore, the baseline idea remains that the northern tier of the U.S. and most of Canada should remain cold toward and probably beyond mid-December. The Southeast could still turn warm despite some shots of colder air.  

Mid-December and beyond is still in the low-skill distant realm. The big story through the weekend will be the significant snowstorm that will affect parts of the Midwest and Great Lakes Region. As a result, Chicago, Detroit, Milwaukee, and Toronto remain on track to experience their snowiest fall in five or more years. As an appetizer, Detroit added 0.1" snowfall yesterday and Toronto picked up 1.2 cm (0.5") yesterday.

Related to this, check out the differences in the means (green) between the +AO of the 0Z GEFS and the slight -AO of the EPS:

GEFS:

EPS:

 With the unfavorable changes in the MJO and AO/NAO, today’s 0Z GEFS is not surprisingly significantly warmer than yesterday’s run for the 2nd week in Dec. However, today’s 0Z EPS, which maintained its very long phase 8, is much colder than yesterday as well as the GEFS:

Yesterday’s 0Z EPS for 12/5-11 2m temps:

 Today’s 0Z EPS for 12/5-11: it’s pretty rare for a 7 day period of the EPS to have that much of a change within just 24 hours:

 As a result, the aggregate of today’s Euro Weeklies 12/1-7 and 12/8-14 2m temp anomaly maps will very likely be notably colder than yesterday’s.

MJO:

Yesterday’s EPS:

Edit: Adding yesterday’s ext-EPS: record shattering 26 day phase 8 Dec 3-28 (current record 18 days)!

Today’s EPS excellent consistency with yesterday with a very long (10+ day) long phase 8: 

Yesterday’s GEFS:

Today’s GEFS hopefully this is off as it went from yesterday’s similar to Euro very long phase 8 to no phase 8 through at least Dec 12th: 

 In summary, mixed results today: fantastic EPS and not so good GEFS. Hoping with the aid of the current major SSW that the EPS will end up the winner for today’s runs!

30 minutes ago, brooklynwx99 said:

this just looks like twitter engagement bait. every MJO forecast has another wave propagating into 8… those plots just don’t go out far enough

It may be Twitter bait. But that’s not because they don’t go out far enough. Rather, it’s that that this Tweet’s runs are “bias corrected” versions, which have more often than not not been making the correct adjustments based on my following them. Here are the corresponding non-bc versions, which are very bullish for phase 8 within their runs:

11/26 ext GEFS: 8 day long phase 8 mid Dec (12/13-20) with a potential 2nd move into phase 8 a few days after this ends:

11/26 ext EPS: extremely bullish 15 day long phase 8 (12/13-27), which would be 2nd longest of all time on record for any month:

1 hour ago, Terpeast said:

Models want to add more ridging across the polar domain. This may be the early effects of the recent SSW and if well timed with the next mjo 8 wave, this could set us up nicely for late dec - early jan. Still expecting a mid month relaxation where we warm up for a week or so. 

 I agree 100% about the realistic possibility that the models have been slow to react to a more -AO/-NAO as potential effects of the current SSWE. Why? I have to look no further back than the 2/16/2023 major SSW. Even on the run of the day of the actual strat. reversal the GEFS was still clueless about the impending drop of the NAO late Feb into mid March:

2/16/23 (day of SSWE) GEFS NAO forecast through 3/2/23 was dead neutral (0) through 3/2/23:

Actual daily NAOs: look how the GEFS run from the day of the SSWE was way too positive for Feb 26th-Mar 2nd!

2023  2 16  0.918
2023  2 17  1.051
2023  2 18  1.202
2023  2 19  1.122
2023  2 20  0.775
2023  2 21  0.480
2023  2 22  0.330
2023  2 23  0.157
2023  2 24  0.155
2023  2 25  0.047
2023  2 26 -0.301
2023  2 27 -0.742
2023  2 28 -0.748
2023  3  1 -0.956
2023  3  2 -1.006
2023  3  3 -1.093
2023  3  4 -1.161
2023  3  5 -1.109
2023  3  6 -1.132
2023  3  7 -1.187
2023  3  8 -1.091
2023  3  9 -0.614
2023  3 10 -0.356
2023  3 11 -0.293
2023  3 12 -0.254

 The next day and the following days, the GEFS started catching on and had this just 4 days later (2/20/23), which was much closer to what actually happened: this was through Mar 6th:

 Similar trends happened with the AO.

 The moral of this real-life story? Stay tuned for more potential big NAO/AO drops for mid December!

Daily NAO:

https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.nao.index.b500101.current.ascii

@donsutherland1

 And here’s even more good trends vs yesterday for cold lovers:

Yesterday’s (11/26) GEFS AO through 12/10: rose to solid +AO of +1:

Today’s (11/27) GEFS AO: neutral/near 0: 

 If the more favorable phase 8 progs today vs yesterday are not enough good news for those who prefer it cold in the E US, I’ve got more:

Yesterday’s (11/26) GEFS NAO through 12/10: headed to moderate +NAO 

Today’s (11/27) GEFS NAO through 12/11: no +NAO as it stops rising at dead neutral (0):

24 minutes ago, Terpeast said:

Yeah, according to hovmollers the models are trending towards weaker forcing at 6/7 after Dec 7. Between now and Dec 7, we have a clean mjo 8 pass. Then weak forcing reappears at 6/7, which is strongest with gefs. But even the gefs begins to propagate that eastward after Dec 7-10. So we may yet get another mjo 8 pass soon afterward.

Yesterday’s (11/26) 2 week EPS (through 12/10): barely made it to phase 8 on Dec 5th-6th before circling back to phase 7 (extended showed it made it back to phase 8 12/13-27+):

Today’s (11/27) 2 week EPS through 12/11: gets to phase 8 on 12/3 and stays through the end of the run (12/11), meaning a 9+ day long phase 8, which would be the longest Dec phase 8 at least since the 10 day long phase 8 of 1989: (tomorrow’s ext EPS will show the total length)

In summary, all GEFS/EPS MJO forecasts are more favorable with regard to phase 8 vs what was available yesterday (2 week and extended). Both of today’s 2 week forecasts (GEFS and EPS) have phase 8 Dec 3-11+.

 Yesterday’s (11/26) 2 week GEFS (through 12/10): didn’t make it to phase 8 (extended showed it made it but not til 12/13):

Today’s (11/27) 2 week GEFS through 12/11: already makes it to phase 8 on 12/3, which is TEN days earlier than yesterday. It remains in phase 8 through the end, meaning it would be a 9+ day phase 8, the longest Dec phase 8 since 1989:

 Yesterday’s (11/26) EPS 2 week MJO forecast through Dec 10th: was then curling back away from 8 after barely getting into it and we were wondering whether it would ever get back to phase 8:

Yesterday’s (11/26) EPS extended, which adds 12/11-27: had a 15+ day phase 8 12/13-27, which would be the 2nd longest phase 8 on record for any month (2nd only to the 18 day long phase 8 of Dec-Jan 1975-6) and the more favorable for cold weak to moderate amp (vs strong) to boot:

Yesterday’s (11/26) GEFS 2 week through 12/10: was then curling back away from 8 and we were wondering whether it would ever make phase 8:

Yesterday’s (11/26) GEFS extended, which adds 12/11-12/27: it turned out that it made phase 8 for an 8 day period (12/13-20), which would be longest phase 8 since Feb of 2019’s 9 day long ph 8 and the longest Dec ph 8 since Dec of 1989’s 10 day long ph 8 along with it being a more favorable for cold weak to moderate amp:

AAM has been verifying much more + than CFS ensemble forecasts have been indicating in the relative short term: if it can’t even get the relative short term right, how credible are these CFS ens. progs?

Today’s (11/27) run has +0.5 to +1.0 late Nov/1st part of Dec:

But look at what earlier runs had for the same period:

11/21 run: -0.25

11/19 run: -1

11/16 run: -1.5

11/11 run: -1 to -1.25

37 minutes ago, donsutherland1 said:

The pattern evolution for the opening 10 days of December still looks very good. With respect to the December 11-25 period, the guidance has shifted. For a time, the GEFS was showing the development of a pronounced AO+ pattern. Now, it has backed off (12z and 18z cycles). As a consequence, the baseline Scenario 1 still seems to be the best one going forward, while recognizing that there is some risk of a break near mid-month. 

The latest ECMWF weekly forecast largely maintains the sensible weather effects from Scenario 1. Given the shifting of the guidance, it makes sense to continue to monitor the teleconnections (and other factors) while reserving judgment for changes until later to avoid making changes based more on model noise than actual developments.

Milwaukee, Chicago, Detroit, and Toronto remain in line for a snowstorm during the November 29-30 period. Significant snow is possible in Milwaukee and Chicago. A moderate snowfall looks reasonable for both Detroit and Toronto. Changes can still occur. WPC is now showing a 70% chance of a moderate winter storm impact in Chicago and surrounding areas for the 24-hour period ending November 30 7 am.

Chicago remains on course to experience its snowiest fall since 2019 (8.3") and possibly even 2018 (12.7"). Milwaukee should see its snowiest fall since 2019 (13.4"). Detroit will likely experience its snowiest fall since 2021 (7.1") and possibly 2019 (9.5"). Toronto could see its snowiest fall since 2020 (23.4 cm/9.2") and perhaps 2002 (27.2 cm/10.7").

Fall 2025 Snowfall Totals (through November 26):
Chicago: 1.7"
Detroit: 2.2"
Milwaukee: 0.6"
Toronto: 12.8 cm (5.0")

 

 Look at how much colder H5 on the Euro Weeklies is compared to yesterday’s: that’s a big change for a 30 day period!

Yesterday’s:

Today’s:

Regarding today’s Euro Weeklies, it’s the most bullish (i.e., colder changes vs prior run) overall in a long time in the NE and SE. I’m not saying they’re cold in the SE,  but they are colder than they were/not as mild or not mild overall. I don’t have time to post details right now, but y’all check it out! Or someone else please post the maps.

Edit: Every one of the 5 weeks is colder and/or less mild in both the NE and SE US vs yesterday’s run including one dramatically colder week. That hasn’t happened in quite awhile.

3 hours ago, John1122 said:

The late month could be, if everything works well, very epic, even beyond this next two weeks with several potential events. The Euro has the MJO in the low amp/c.o.d into late December/Early January. @GaWx has noted that essentially every low amp pass through 8 has coincided with well BN temps, but that high amp passes were not always cold in the east. 

East Asia should become more favorable soon, to allow west coast ridging downstream as well.

Hey John,

 Thanks for bringing up the amp. What you said generally coincides with my thoughts. But I’d like to clarify what I’ve said just to make sure there’s not a misunderstanding. Indeed, various analyses I’ve done over the last 10-11 years or so, which all have involved calculations of actual temperatures in a place or places in the E US, have shown that the average anomalies have tended to be colder with low to moderate amp (1.7 or lower in my latest study, which was 8+ day long phase 8s) vs strong AMO of phase 8. But not “essentially every low amp pass”. It’s more like a majority of low amp have been cold vs pretty balanced for high amp.

 Today’s MJO through 12/10: tune in tomorrow to see what they’ll do 12/11-27:

On 11/25/2025 at 9:18 AM, FPizz said:

Is the ext available to compare the same outputs?  Maybe instead of doing the loop in phase 7, it does it right on the line between 7/8 then goes back into 8.  Yesterdays did the loop in 7

So, now I can give you the answer

Yesterday’s 2 week GEFS (through 12/9/25) was starting to loop in 7 through the end of the 2 week run: was it going to stay in 7 or was it going to go into 8?

 Here’s the much anticipated answer: it ended up doing just a small, quick loop in 7 but then it went a little ways into 8 on 12/11. But that little ways was enough for the moderate amped 8 to last 8 days (12/11-18), which alone would be enough for the longest Dec phase 8 since Dec of 1989’s 10 days and longest, period, since Feb of 2019’s 9 days. However, it then looped back into 7 a little ways 12/19-26 with it stalled at the end. Now my question is whether or not it would have gone back into 8: we’ll never know that far out on this run

4 hours ago, GaWx said:

The colder trend for early Dec is happening on all ensembles including GEFS: these are all for a week from today at 7PM: watch the SER disappear:
 

 

@donsutherland1@bluewave

 The above noted colder GEFS trend for early Dec continued with the 12Z run.

51 minutes ago, TheClimateChanger said:

Interesting. At least at looks to be moving through at a pretty good clip, so might just be a temporary excursion in Phase 8.

That ext Euro phase 8 lasts 11 days, which would be the longest in Dec since 1975. I just hope it actually gets there and stays for awhile rather than curl back to 7 to stay.

24 minutes ago, FPizz said:

Is the ext available to compare the same outputs?  Maybe instead of doing the loop in phase 7, it does it right on the line between 7/8 then goes back into 8.  Yesterdays did the loop in 7

1. No, ext for same run comes out a day later.

——————

2. GEFS 2 days ago:

GEFS yesterday: gets to phase 8 five days earlier than any other GEFS as of then:

GEFS today: curled back very slightly vs yesterday (E US cold lovers wouldn’t want a curl back into phase 7) but very similar to yesterday/look how different it is vs 2 days ago!

Yesterday’s Euro: phase 8 starts 12/14:

Today’s Euro: phase 8 starts 10 days earlier, 12/4, (with a 6+day long phase 8 implied) although I’d want to make sure it isn’t curling back into 7 and staying there:

last time Dec had a 6+ day long phase 8 was way back in 1995 (12/20-5):

Euro Weeklies 2m temps for 11/24-30 and this is before the very recent cooldown for early Dec:

11/17 run:

11/24 run:

The colder trend for early Dec is happening on all ensembles including GEFS: these are all for a week from today at 7PM: watch the SER disappear:
 

@donsutherland1@bluewave

11 minutes ago, donsutherland1 said:

That’s one possible factor that has led me to continue to monitor the period. By the end of November, I think there will be greater clarity.

 I’m wondering if despite the clear warming trend of the Euro Weeklies related to its insistence of a stubborn potent SER along with the current progged switch to a +AO if there’s lower than normal confidence due to a combo of the MJO taking a track that’s often cold (though far from always as we know) and the current very weak SPV, which typically takes 2+ weeks to bring the E US persistent dominating cold.

 I didn’t pick up on this earlier and don’t know if anyone else posted this. Today’s GEFS has phase 8 starting on Dec 8th, which is about 5 days earlier than any other run: