GaWx

I agree to take any of these forecast maps with a grain of salt like I usually do. I‘m not debating that at all. Absolutely! Seasonal modeling is typically not high confidence for me. They can sometimes provide good hints though. I was just debating where you’re saying the JMA H5 trough axis is located. And now I’m going to also respectfully debate you saying there’s a ridge on the E coast. This JMA’s H5 ridge axis looks well out in the Atlantic to me. Why do you say it’s on the E coast? We are definitely going by different definitions.

The following example of a (positively tilted) trough axis goes by the definition I’m using, which is where it is from W to E and which you’re not using: The JMA H5 trough axis for Jan is well E of the Plains (3rd map) (and positively tilted). In the Plains, the lines are from WNW to ESE as opposed to from W to E, meaning the trough axis is well E of there:

Chris, I respectfully disagree with you. You and I are going by a different definition of trough axis. I go by where it is from W to E, which is the official definition. It looks like you’re going by where the anomaly is most negative (darkest blue). Based on where it is W to E, it clearly goes from just E of Hudson Bay to Western Lake Erie to the Central Gulf Coast. If one looks closely and takes into account that this map is tilted by tilting the phone/screen, one can see that at Chicago it is still slightly S of due E rather than straight W to E. So, I still say the JMA H5 trough axis for Jan is well E of where you’re saying it is.

The southside of Atlanta/airport E to Augusta and into SC had a bad ZR in Feb of 2014. That one took down the Eisenhower Tree at Augusta National. In my area, where ZR events are typically few and very far between, we had a rare 1/4” of ice accretion from 1/2” of ZR in the great SE coastal winter storm of early Jan of 2018. It stopped just shy of causing widespread, major problems.

SST anomalies in Nino 3.4 continue with their big drop: OISST as of 12/14: new low CRW as of 12/15: new low CDAS as of 12/16 6Z: ~tied for its lowest though it’s cold biased The equivalent daily RONI is likely now well into moderate range.

Chris, Regarding the bolded, why are you saying the latest JMA has the mean trough axis in the Plains? The H5 map (last one) looks to me like it has it well E of that from just E of Hudson Bay SSW to Lake Erie/Ohio to the NE to central Gulf of Mexico (+ tilt). That’s 750-1,000 miles E of the Plains. I’m talking about where H5 is west to east. In the Plains it is WNW to ESE.

Predictably, the 0Z Euro isn’t as cold as the very cold 12Z run on 12/23-7 and doesn’t have that Christmas snow. The 0Z GFS cooled since 12Z but is still not as cold as the 0Z Euro.

18Z Euro ensemble means at 144 are similar to the cold 12Z EE at 150 and continue to suggest much colder than GEFS (18Z) and similar cold to the GEPS (12Z). So, the prospects for strong cold suggested by the 12Z Euro have survived at least through the 18Z as far as it goes out. 0Z will be much more telling.

Now for some much later periods of speculation for the SE temps **fwiw**: -The new Euro Weeklies mean (100 member ensemble) has no strong signal for another long period of torch after the upcoming week. -After next week’s chilly week, they have near normal/no strong signal 12/30-1/5. -They are showing quite a strong cold signal for being out at week 4 (for 1/6-12). This may be the next period to watch for potential excitement. I’m pretty interested myself based on the persistence of these weeklies runs. -They have a weak cool signal for 1/13-19. -They have no signal either way for 1/20-6.

This thread is no longer needed due to the 12Z Euro.

12Z Euro ens mean is very cold for 12/22-5, especially 12/22-4. It’s about the coldest run yet in our area for 12/22-5. Of course, it isn’t as cold as the operational. Edit: ~25% of the 50 runs look interesting for wintry precip potential even outside of the mountains

I just looked at TT 2m and they also agree with WxBell. So, the temps aren’t a WxBell issue here. So, now the question is whether or not to expect this to closely verify being that Christmas is still ~10 days out (fantasyland for an operational) and that the Euro is so much colder than the 6Z Euro AI, the 12Z GFS, and the 12Z CMC. So, this is a huge outlier. When looking at possibilities, I look at this as the extreme of numerous possibilities. So, at this point I say the odds are very low and to not be surprised if Christmas is way warmer than this. Buying into runs like this often leads to unnecessary disappointment. There’s often way too much significance placed on operationals past day 7. Ensemble means are way more credible day 7+.

Euro Weeklies coldest yet Jan 6-12 of the 17 runs and by a good margin! H5: now has even lower hts in Aleutian low position and the mean ridge is slightly further E allowing for even stronger +PNA along with some -EPO; note how E N.A. sticks out like a blue thumb on global view: for week 4 this is quite a strong signal for cold: 2 meter temps show easily the coldest yet of 17 runs for the E US: Global view of 2m: IF this is a real threat for cold that week as opposed to a head fake, the anomalies would likely grow substantially as we get closer as that’s how ensemble means usually work. At 4 weeks out, it is rare to get substantially sized areas colder than the 2nd level. This map for week 4 has a substantially sized 2nd level of cold.

I’m trying to figure out why the 12Z Euro is so much colder in the SE vs the 12Z GFS 12/22-7 on WxBell. Does that look right? Of course this is days 7-12 (much of it in fantasyland for an operational) and thus don’t buy how ridiculously cold it is at 2 meters, especially on these WxBell maps. The 850s are similar to TT’s, regardless. The 2 meters aren’t out there yet.

Thanks, Don. Along with the actuals for 12/1-15, GEFS two week forecasts continue to suggest a good chance for a record high tabular PNA for a non-Nino Dec (records back to 1950)…keep in mind that the tabular monthly values of +PNA months have averaged ~~1.8 times the amplitude based on the daily values shown in the charts that are updated every day. Thus, it looks to me as of now that Dec will likely come in ~+1.5 to +1.75. I roughly estimate 12/1-15 to be +1.60 (based on using a 1.8 conversion factor): The 5 highest tabular Dec +PNAs for non-Nino on record (2024 progged to have good chance to be new highest): 2020: +1.58 1960: +1.46 1985: +1.39 2005: +1.38 2000: +1.23 Thus, a record high non-Nino Dec PNA is quite possible. Subsequent Jan PNAs for these 5 non-Nino high PNA Dec: 2021 +0.19 1961 +1.41 (4th highest on record for non-Nino) 1986 +0.97 (tied for 7th highest on record for non-Nino) 2006 +0.43 2001: +1.51 (3rd highest on record for non-Nino) Avg Jan for these 5: +0.90 So, whereas the above has one case coming in just neutral for Jan (2021), it appears that the chances for a +0.75+ PNA in Jan are pretty good. The following 9 non-Nino Jans since 1950 had a +0.75+ PNA (all cold ENSO except RONI neutral 1961 and 1981): Year/PNA/E US temps (7 of 9 Jans cold/none mild): 1961 +1.41 cold 1981 +2.42 cold 1984 +0.97 cold 1985 +1.63 cold 1986 +0.97 normal 2001 +1.51 normal 2011 +1.29 cold 2014 +0.97 cold 2022 +1.01 cold Here’s the average of these 9 Jans using 1981-2010 normals:

Good info! To supplement your data, check this out: LOT avg low D/J/F 10 year periods; avg of DJF 1951-60: 23.2/18.4/22.3; DJF 21.3 1961-70: 21.4/14.6/19.2; DJF 18.4 1971-80: 21.5/12.8/18.1; DJF 17.5 1981-90: 18.3/14.6/18.6; DJF 17.2 1991-00: 22.0/16.4/22.4; DJF 20.3 2001-10: 21.3/17.9/19.1; DJF 19.4 2011-20: 25.3/17.4/19.1; DJF 20.6 So, imagine growing up there in the 1950s. It got significantly colder during the 1960s-80s before warming back significantly 1990s-2010s. But the warmest decade of these is still the 1950s. So, compared to their childhood, the 2010s were about the same. The 1960s-1980s were cold. Someone growing up in the 1980s could have been spoiled by how cold it was being that it was unusually cold that decade. https://www.weather.gov/wrh/Climate?wfo=lot

The latest available bias corrected extended EPS, CFS, and BOMM ensemble means all have the MJO reaching the left side of the diagram mainly at moderate to weak amplitude in early Jan, which though not nearly always have more often than not been associated with a cold dominated pattern in the E US in the first half of Jan during non-Nino ENSO: EPS bc: CFS: BOM: Here are non-Nino ENSO weak (near or inside circle) to moderate left side MJO dominated E US 1st half of Jan with diagrams shown for coldest: 2023 mild 2022 cool NE/mild SE 2002 slightly AN NE/cold SE 1999 cold: 1997 normal 1996 cold: 1994 cold: 1985 cool:

Charlie, doesn’t a weaker PV usually mean overall colder for the middle latitudes since the cold wouldn't be as locked up in the more N latitudes?

Indeed, the 0Z GFS is significantly warmer for 12/19-20 than almost all other runs the last few days. But cheer up, today’s Euro Weeklies were the coldest run yet for Jan 6-12. Edit: However, the consensus has also cooled some for 12/22-5/6.

It’s interesting that we’re having the coldest first half of Dec in the E US overall in a good number of years (since 2010 in many cases) and that this is during a robust MJO 4-5, which has more often than not been mild in Dec and averages mild. The +PNA has been one of the strongest for this period on record. *Edit: For non-Nino since 1950 only these had a similarly strong +PNA during 12/1-15: 2020, 2017, 1989, 1988, and 1960. *Edit 2: Of the above 5 strong non-Nino +PNA during 12/1-15, only 2020 and 1960 held on with a solid +PNA most of the rest of the month like is progged by the GEFS for 2024.

Plus strong non-Nino +PNA/cold Dec analogs suggest to at least be wary about the slightest hint for cold in Jan. Indeed the week 1/6-12 is the coldest for it at sfc and at H5 in the E US of any run yet (going back 16 runs) by a good margin. More strikingly, look at how much the 1/6-12 BN H5 in E NA sticks out on this global view, which tells me it is a very strong signal especially for being still out at week 4 (a rare occasion that far out on EWs to see that large/intense BN H5 in the current warming era): Note fwiw that the ridge is centered W of this month’s W NA ridging allowing a stronger -EPO, which may mean even colder anomalies especially up north.

Parts of upstate NY, Ontario and Quebec appear to be near or at all-time Dec record high SLP with the Massena to Ottawa corridor at ~1050 mb near records for any month: these are from 10AM EST: CITY SKY/WX TMP DP RH WIND PRES REMARKS MASSENA SUNNY 18 10 71 NE3 31.01S MONTREAL MOSUNNY 16 7 67 N5 31.00R WCI 9 TC -9 _____REGIONAL ONTARIO LOCATIONS_____ CITY SKY/WX TMP DP RH WIND PRES REMARKS OTTAWA MOSUNNY 14 9 79 NE7 30.99R https://ca.news.yahoo.com/record-breaking-pressure-over-ontario-012208535.html

Parts of upstate NY, Ontario and Quebec appear to be near or at all-time Dec record high SLP with the Massena to Ottawa corridor at ~1050 mb near records for any month: these are from 10AM EST: CITY SKY/WX TMP DP RH WIND PRES REMARKS MASSENA SUNNY 18 10 71 NE3 31.01S MONTREAL MOSUNNY 16 7 67 N5 31.00R WCI 9 TC -9 _____REGIONAL ONTARIO LOCATIONS_____ CITY SKY/WX TMP DP RH WIND PRES REMARKS OTTAWA MOSUNNY 14 9 79 NE7 30.99R https://ca.news.yahoo.com/record-breaking-pressure-over-ontario-012208535.html

From FFC: WILL BRING FLOW AT 850MB FROM THE EAST TO THE SOUTHEAST AS A MASS RESPONSE TO THE DEVELOPING LOW. HOWEVER, SIMULTANEOUS TO THIS, STRONG SURFACE HIGH WILL SET UP SHOP OVER THE NORTHERN APPALACHIANS, WHICH THE WEATHER WEENIES WILL KNOW BRINGS COLD AIR DAMMING (THE WEDGE) TO OUR CWA.

Newest from BAMwx: I haven’t watched it yet. Hoping it like the last couple provides sound reasoning for cold Jan and doesn’t hype: