GaWx

Latest CFS mean +AAM back a bit stronger again for late Dec/early Jan (El Ninoish despite it also rapidly cooling 3.4):

The CFS mean of the last 10 days is still going with record shattering rate of cooling from Nov to Dec in 3.4 though I don’t believe it will cool as drastically and is one reason I say to take the CFS extended temps for the US with a humongous grain:

Taking CFS extended with a huge grain so fwiw:

I feel this is bordering on hype as I’m seeing no evidence of above climo chance at major SSW later in the month at least as of now though I’ll continue to follow: Despite what he says: So, why is he saying “major stratwarm to develop later in the month”? Major stratwarm requires 10 mb wind reversal. Euro says 2% chance and GEFS says 0%.

The 1st week of Dec at KSAV has a shot at ending up the 6th coldest since 1874! Only colder for sure assuming I didn’t miss others: 2000, 1910, 1896, 1886, 1876. 1944 was very close. Low today 25, coldest of season so far. Edit: 2024 ends up tied with 1944 for 6th coldest 1st week of Dec since 1874. When taking into account warming climo, 2024 looks like it is the 3rd coldest 1st week in Dec behind only #1 1876 and #2 2000!

The 1st week of Dec at KSAV has a shot at ending up the 6th coldest since 1874! Only colder for sure assuming I didn’t miss others: 2000, 1910, 1896, 1886, 1876. 1944 was very close. Low today 25, coldest of season so far. Edit: 2024 ends up tied with 1944 for 6th coldest 1st week of Dec since 1874. When taking into account warming climo, 2024 looks like it is the 3rd coldest 1st week in Dec behind only #1 1876 and #2 2000!

Thanks. Based on this run, I’d be most excited from a cold perspective if I were in, say, Minneapolis. Also, as Chris knows well, the models often are cold biased in the E US due largely to the warm MC. So, what often happens if that they verify warmer in the E US vs what they show as the SE ridge verifies more strongly (i.e., leading to cold bias of models)

Just to clarify for the readers, the last week, indeed, has an impressive cold area but it’s bottled up in SW Canada, N Rockies/Plains, and upper Midwest (Ninalike) with not much of a push SE from week 5. The SE ridge is then keeping the cold from the E US and making it mild in the deep SE, a common pattern during La Niña. I’ve seen many cases like this that only allow any cold to slowly seep SE and never cool the SE/Mid Atlantic that much. From the E US perspective, these situations make this “wasted cold”. Long way to go and it will change many times for better or worse, but that does fit Niña and warm MC climo well: Here’s the week prior (week 5): @bluewave

The one thing I hope doesn’t verify is the SE ridge of the final week, something a La Nina tends to favor and why I like El Niño much more: I want the +PNA to return/W ridge too far W!

New Euro Weeklies: stronger SPV (NN) vs yesterday’s slightly weak SPV; any hints of late Dec warming are reduced vs yesterday’s run: climo favors any possible major SSW this winter to be later than this, regardless: Fwiw, Christmas week has cooled on the new Euro Weeklies with mainly NN E US (no torch):

Latest EPS (0Z) based HDD: that second spike centered on Dec 12th had increased the last couple of days (though 12Z backed off some I think) but otherwise week two is mainly mild:

Latest available CFS ens based AAM: still positive but not as strongly positive in late Dec and early Jan as prior runs (these often jump around and aren’t reliable): Prior run:

Based on the +QBO/high solar analogs (thank you Dr. Dewpoint (Joe D’Aleo) for inspiring me to check): If it looks like DJF SSN is going to be 135+ (don’t know yet as Dec has started out lower), I’m going to increase the chance in my mind for a major SSW to likely this winter/early spring from the moderate chance I previously felt was the case.

I thought that when you said, “I think being near solar max as opposed to ascending 2 years ago is somewhat less favorable” that you were impying the chance for an SSW this winter being lower than that of two winters ago because it’s no longer ascending. So, you’re not saying that?

Based on the analysis I just did due to what Joe D’Aleo said about the correlation of high solar/+QBO to SSWs, I don’t agree with you about ascending vs descending in this particular situation. Here’s why: Solar DJF 135+/west QBO: 57-8: SSW 1/31/58 about right at peak 59-60: SSW 1/17/60 descending 69-70: SSW 1/2/70 descending 78-9: SSW 2/22/79 ascending 80-1: SSW 2/6/81 descending 90-1: no SSW descending 99-00: SSW 3/20/00 ascending 01-02: SSW 12/31/01, 2/18/02 descending So, these +QBO major SSWs that occurred during high solar were as follows: - two ascending - one near peak - six descending - So, three times as many during descending as ascending - So, I don’t think that if 2024-5 winter turns out to be descending (but still 135+) that that itself would necessarily reduce the chance for a major SSW - However, the criteria requires DJF SSN to exceed 135. If it falls to below that, then winter 24-5 wouldn’t even qualify as high solar (135+) and thus the correlation of high solar/W QBO to SSW frequency would no longer be relevant. https://www.sidc.be/SILSO/DATA/SN_m_tot_V2.0.txt

Unlike yesterday’s BAMwx tweeted hype showing that extreme record-breaking 6Z CFS way out in mid-Jan, this (along with his Wednesday video) is well presented by Michael Clark with minimal or no outright “hype” showing his ideas of a mainly warming rest of Dec followed by realistic potential for a cold Jan (many models are shown rather than just the CFS and the CFS shown is not a cherry picked extreme WeatherBell map):

Unlike yesterday’s BAMwx tweeted hype showing that extreme record-breaking 6Z CFS way out in mid-Jan, this (along with his Wednesday video) is well presented by Michael Clark with minimal or no outright “hype” showing his ideas of a mainly warming rest of Dec followed by realistic potential for a cold Jan (many models are shown rather than just the CFS and the CFS shown is not a cherry picked extreme WeatherBell map):

This video along with the Wednesday video were well presented with little or no outright hype. These are in contrast to yesterday’s BAMwx tweet showing the extreme WeatherBell map from the 6Z CFS, which I still think was cherry-picking hype to get more clicks. Many folks who read it don’t have the knowledge to realize that the chance of that verifying closely is extremely small being that it would be record breaking mid Jan cold. But again this and the Wed. video were well done imho.

New Michael Clark (BAMwx) video followup from early this morning: again like the Wednesday video, this is well presented with little or no outright “hype” (unlike yesterday’s tweet about the cherry picked extremely cold mid Jan portion of yesterday’s 6Z CFS) and he does talk about a bunch of models rather than just the CFS and the CFS shown is not a cherry picked extreme WeatherBell map:

I’m very confident BAMwx (and assume Don agrees) wasn’t implying yesterday’s extreme 6Z CFS maps with (near) all-time record cold in mid-Jan would necessarily verify closely/literally. But what I think Don and I agree on is that tweeting that extreme 6Z 12/5 CFS way out at weeks 5-6 (and the typically too cold WB version of it to boot) is hype to get more clicks and is cherry-picking. Many folks looking at that aren’t going to understand that the chance of that verifying even closely is extremely low. He did say that the CFS was “on board” with his ideas when he showed that run. I think it was a poor decision to post that map even though it was just for illustrative purposes. As I posted, the very next CFS run (12Z) was literally 23-5F warmer for that mid-Jan week. As I posted on Wednesday, I felt Michael Clark’s Wednesday video was overall well done as far as clearly communicating his general feeling about the warming Dec pattern and cold Jan potential. But then a day later (yesterday) BAMwx tweeted that extreme 6Z CFS, which I didn’t like.

Per Joe D’Aleo at WB: “Strat warm favored in west QBO near solar max” I checked it and by golly I think he has a point: Solar DJF 135+/west QBO: 57-8: SSW 1/31/58 59-60: SSW 1/17/60 69-70: SSW 1/2/70 78-9: SSW 2/22/79 80-1: SSW 2/6/81 90-1: no SSW 99-00: SSW 3/20/00 01-02: SSW 12/31/01, 2/18/02 -So, of these 8 high solar/+QBO winters, 7 had at least one major SSW and one had two! - earliest 12/31 - 3 in Jan - 3 in Feb - 1 in Mar - So, perhaps one will actually be likely this winter should DJF SSN be 135+. SSN: https://www.sidc.be/SILSO/DATA/SN_m_tot_V2.0.txt

The very next WB CFS ens run (12Z) map for the same period was ~25F warmer at Chicago, Great Falls and Madison and was ~23 warmer at Indianapolis:

Thanks, Mitch. I’m curious. Why is just a weakened PV better than (major) SSW? I know they haven’t all resulted in a cold E US within a few weeks afterward. But a decent number have done that, some impressively so. They may do better though when we don’t have a preexisting strong -PNA/strong SE ridge. That muted and shortened the cooling from the mid Feb of 2023 major SSW even though we in the SE got a chilly week in early to mid Mar (coldest in quite awhile).

The 12Z WB CFS ens mean temps are not surprisingly much warmer than the 6Z WB CFS for 1/9-15 even though it is still pretty cold in a smaller area 6Z: Chicago ~25 BN 12Z: Chicago ~5 BN

I’ve been focusing on temps. However, I’m also leaning toward WB CFS H5 runs averaging too low. I’ve seen numerous WB CFS H5 maps with blue colors dominating the hemisphere, which isn’t realistic in a warming world since avg H5 is also rising. Regardless, BAMwx cherry picked a very cold CFS ens late in the run, which is my point.