GaWx

I'd agree with your post if you changed one word, "no". I wouldn't at all say "no" value. That is simply not true. Your overall point of not relying on model output is understood but saying no value is hyperbole. Thus I still see plenty of value and thus will continue to follow and post model output.

I’m still amazed at how the Euro weeklies went from this trend, which covers through the 12/24 run: followed by the strongest signal for an early Jan major SSW (the 12/26 run), to the weakest signal for an early Jan major, the 12/28 run as noted in my post earlier this morning. Simply astounding!

Yesterday’s 0Z EPS mean (0Z 12/28/23 run, latest available as of now on these graphs) went even further from the expectation of a major SSW in early Jan with only 4 members (8%) having one vs 20% on the 0Z 12/27 run per Allan. This 8% is only two days after the most impressively weak SPV for any 0Z run in early Jan, the 0Z 12/26 run (see 2nd of two graphs just above this in quoted post), a most unexpected turn of events!

Based on the tweet from Allan saying only 20% major SSWs on today’s 0Z EPS, here’s what some of us have been waiting for to see if it agreed: it seems to be in agreement in being much less impressive in early Jan! The mean dips down only to +5 on Jan 6th vs yesterday’s -3: Compare that to the very impressive run from yesterday at 0Z, what then was about the most impressive yet with a dip of the mean to -3 on Jan 6th: So, that means that today’s 0Z EPS, GEFS, GEPS, FNMOC ens, and GFS are all less impressive than 24 hours ago. Will we now get a @mitchnickstyle reversal tomorrow? Stay tuned!

I think that the subsurface already peaked in Nov.

Here are the 0Z 12/27 model means for the 60N 10 mb wind low point for the GEFS, GEPS, FNMOC ens, and the GFS along with the respective comparisons to the 4 prior days’ 0Z: 1. GEFS: 12/27 +11 vs 12/26’s +8, 12/25’s +6, 12/24’s +18, and 12/23’s +17 2. GEPS: 12/27 -4 vs 12/26’s -9, 12/25’s -16, 12/24’s -2, and 12/23’s -5 3. FNMOC ens: 12/27 0 vs 12/26’s -3, 12/25’s -2, 12/24’s -2, and 12/23’s +7 4. GFS: 12/27 +8 vs 12/26’s -1, 12/25’s 0, 12/24’s 0, and 12/23’s +32 All four dipped to lows 12/25-6 followed by a rise today. Despite today’s rises, the runs are still significantly lower than the 12/23 runs except for the GEPS being ~same. GEFS has been the highest overall while GEPS has been the lowest. Keep in mind that we’re still ~9-10 days out from a potential crossing of the 0 line, still a fair ways out to allow the details to be pinned down yet. If the low were to turn out, say, +2 vs -2, I don’t think it would make much difference as far as potential effects on the troposphere in the US, whether significant or not. Now comparing something like, say, +5 vs -5 would likely be a different story obviously. Being that lows were hit just 1-2 days ago and it is still ~9-10 days out, another reverse downward could easily happen as per @40/70 Benchmark 's post from two hours ago:

Per Allan’s same source, the % on the EPS fell a little more from the 25% (13) he showed per yesterday’s 12Z to only 20% (10) on today’s 0Z. We’ll be able to compare this with the Euro Weeklies output this afternoon to make sure they agree:

Based on comparing the GEFS runs of 0Z 12/25 and 0Z 12/26, the main reason for the small rise in the mean wind from the ensemble mean was not the % of members with a major SSW but rather the average intensity of the majors was a little softer on the 12/26 run. But in terms of frequency, the 12/26 run is still one of the most bullish for the lagging GEFS for Jan 5-11 with 10 (32%) majors vs 11 (35%) on the 12/25 run.

I wonder where he gets these graphs from. Something doesn’t seem right.

OHC continues to plunge:

Also, 1986-7 and 2015-6 El Nino winters had both under an inch through Dec and 20”+ Jan+. So, there have been four and all four had 11.6”+ in January, alone. Since 1939-40, there have been 10 El Niños with <1” through Dec. That’s out of 28 total El Ninos. So, 36% of them had <1” meaning not highly unusual. Thus out of those 10, four (40%) had 20”+ Jan+. That’s not that low of a %. I’ll now compare to non-Nino winters. Regarding non-Nino winters since 1939-40, I count 13 with <1” through Dec. That’s 13 out of 56 non-Nino or 23% of them. So, having <1” through Dec has been significantly more unusual during non-Nino (23%) than during Nino (36%). Out of those 13 during non-Nino, only 4 (31%) ended up with 20” Jan+ vs the 40% for El Niño. So, being in El Niño helped some for the slow starters. Out of all 84 winters since 1939-40, 41 of them (49%) had <20” Jan+. So, not getting 20”+ Jan+ is nearly a coin flip for all winters. Out of the 23 total winters with <1” through Dec, 15 (65%) had <20” Jan+. That means that out of the 61 total winters with 1”+ through Dec, 26 (43%) had <20” Jan+ vs the 65% for winters with 1”+ through Dec. So, having <1” through Dec does increase the chance somewhat for Jan+ to have <20”.

The # of members with a major during just Jan 5-12 went from the 0Z 12/24 GEFS’ one (3%) to the 0Z 12/25 GEFS’ 11 (36%)! I’m getting very close to the @40/70 Benchmarklevel of confidence that there will be one in early Jan.

So, the 12Z EPS is implying a most likely major SSW (when winds reverse) centered on Jan 6th. Per the 0Z, the most likely reversal dates appear to be for Jan 5th-8th. The 0Z was the first 0Z EPS with the mean touching 0 m/s. The lowest prior to that had been yesterday’s +2.5. And now this 12Z drops it to -5! A Jan 5-8 SSW date would suggest the period of greatest potential cooling from it on the E US would start ~Jan 20th and go at least well into Feb meaning covering a large portion of the best climo period for E US winter storms, especially.

1. That looks like a major SSW (with a split) on the 12Z GFS. The 0Z was right at 0. 2. The 0Z CDN ens mean dropped way down to -16 vs -3 yesterday (see below). A -16 for an ensemble mean 14 days out is extremely impressive! Anything -15 or under would be a record breaker for late Dec through mid Jan and there have been many in early Jan, alone. 3. The 0Z GEFS mean dropped way down to +7 vs +17 yesterday (see below):

That Atlanta to Carolinas major snowstorm was on Jan 2-3 and the SSW was on Jan 2nd. So, it’s likely that the snowstorm occurring had little to do with the SSW.

Agreed 100% about the difficulty in estimating what would have occurred without a SSW should one actually occur.

The MJO progs from the model consensus of early Dec were much too weak for late Dec: near circle (top image) vs actual well outside the circle (bottom image):

The model consensus continues to go in the direction of a split major SSW in early January. Almost all of the El Niño years with them had following the splits significant periods of notable cold and/or winter storms, including some wintry precip quite far south (like N Florida).

Following up on this, the GEPS mean had a major 14 days out yesterday and 13 days out today vs having to wait til 10 days out in advance of the 2/16/23 major. So, its signal is much stronger than then. OTOH, the GEFS mean in advance of 2/16/23 was ~+10 or less from 15 days out before also going major 10 days out. But with it still up at +17, it is a much weaker signal than that of GEPS vs having a stronger signal than GEPS 15-14 days in advance of 2/16/23. So, there are mixed signals between the GEFS (less bullish) and GEPS (more bullish) vs last year. Based on my memory, the EPS is stronger than it was then. So, two of the three ensemble means are more bullish currently vs 2/16/23 and one is less bullish. I expect the GEFS to get more bullish on the coming days.

0Z 12/24 (orange) barely makes major SSW status with it a hair under 0 m/s at the end and still dropping. The 0Z CDN ens mean (blue) is at 2 days in a row at a major. But the 0Z GEFS mean never gets below +17.

The 0Z 12/24/23 EPS holds onto the very good chance for a major SSW Jan 3-9. Also, I count ~12 extreme cases (sub -15) throughout the run:

And we can now add the 12Z GFS op to the split SSW list. Here’s the way I look at the SPV: -Weak much better than strong -SSW better than not -Major SSW better than minor. E 1/3 of US affected most. -Split major seems to be somewhat better than displacement major -Split during El Niño may be best of all though displacement during Nino normally good enough

Here is a screenshot of a list of major SSWs broken down by split vs displacement: noteworthy splits include 1/30/58 (El Nino), 1/8/68, 2/2/73 (El Nino), 1/9/77 (El Nino though not listed), 1/2/85, 12/8/87 (El Nino), 1/18/03 (El Nino), 2/9/10 (El Nino), and 1/2/19 (El Nino; too recent to be listed here but was a split). Note that there have been 7 split SSWs since 1958 during El Nino that were early enough to impact met. winter and all 7 were notable in terms of subsequent cold and/or historic E US winter storms:

The 0Z EPS is also hinting at a split per this that just came out from BAMWx (left map is 0Z EPS hour 360 at 50 mb) meaning all three of the latest major ensemble means are leaning toward a split now:

So does the 0Z GEPS (CDN ens):