GaWx

Plentiful rain on and off mid afternoon through now with thunderstorms included during the afternoon. Very gusty winds in the 40s this evening with the cold front totally unexpectedly knocked out my power ~11:30PM. So, these winds weren’t associated with thunderstorms, which occurred hours before. Now a light chilly rain with ~50 as I await with candlelight for my power to return. I hear generator(s) running. Update: Power back on 12:20AM, yay! (just under an hour out…not bad).

All of the sudden, today’s Euro Weekly for 1/8-15 came in much colder than yesterday and is the coldest for that week since it started being covered on Nov 30th: Also, today’s 12/25-1/1 isn’t quite as warm as yesterday’s.

Today’s Euro Weeklies SPV is significantly weaker in late Dec and early Jan than for any recent run. There are far more members with a major SSW in early Jan and there are even 6% Dec 27-31 after there being only one on the prior 3 runs, combined. Just for 12/27-1/7, alone, I count ~30%! Then for 1/9-16, I count a whole lot more. This is the first run with a clear majority of members with one (60%+). (For the stat nerds like me, I see ~23 sub -10, 8 sub -15, 4 sub -20, 2 sub -25, and 1 sub -30.)

The prelude to any potential upcoming major SSW is starting to get in range on the non-extended GEFS. The Siberian warming on this 12z GEFS 384 is stronger than what’s been on earlier runs fwiw. These runs will be watched over the upcoming week to see whether or not an actual major SSW appears to be coming. For a major, it isn’t just the warming, itself. It is the reversal of mean 60N winds at 10 mb that defines it:

The way things have been trending on recent Euro Weeklies, we may need a major SSW for multi-week cold potential. Hopefully for cold lovers they’ll reverse back colder. But yesterday’s Euro Weekly 2m temp map for 12/25-1/1 was the warmest run yet for that week for the E US (and yesterday’s 1/1-1/8 was also its warmest though not nearly this warm with the only E US BN suggested in the far SE US):

How have SE US temps been 1-3+ weeks following major SSWs (per ERA) in winter during El Niño? (Excluded 2/29/80 and 2/24/07 because too late to affect met winter) 1/31/58: very cold Feb 12/16/65: very cold mid Jan to early Feb 11/28/68: cold Dec & 1st half Jan 1/2/70: very cold Jan, cold Feb 1/31/73: cold mid to late Feb 1/9/77: very cold mid Jan-mid Feb 1/23/87: very cold mid to late Feb 12/8/87: cold took 3 weeks to start (very late Dec) and continued through Feb 1/18/03: cool late Jan-early Mar 2/9/10: very cold mid Feb-early Mar 1/2/19: cold mid to late Jan -So, ~half of Ninos since 1958 had a major SSW per ERA by mid Feb. vs 40% of others. -So, for the 11 that had one, all (100%) had BN temps in the SE dominating for a 3-8 week period starting 1-3 weeks after the major SSW date. Conclusion: Due to unanimous agreement of the 11 Nino cases: if a major SSW actually occurs in early Jan, I’ll be expecting a 3-8 week period of SE US BN domination starting mid or late Jan and ending anywhere from early Feb through early Mar. If instead one occurs in mid Jan, push these dates out 1-2 weeks. So, most likely period of cold due to major SSW in early to mid Jan would be late Jan-early Feb. It is possible that it will already be cold during or before any major SSW. I’m talking about aftereffects from the SSW, itself. https://en.m.wikipedia.org/wiki/Sudden_stratospheric_warming

How have E US temps been 1-3+ weeks following major SSWs (per ERA) in winter during El Niño? (Excluded 2/29/80 and 2/24/07 because too late to affect met winter) 1/31/58: very cold Feb 12/16/65: cold Jan mid-Atlantic south 11/28/68: cold Dec & 1st half Jan 1/2/70: very cold Jan, cold Feb 1/31/73: cold mid to late Feb 1/9/77: very cold mid Jan-early Feb 1/23/87: cool Feb 12/8/87: cold took 3 weeks to start (very late Dec) and continued through Jan 1/18/03: Feb very cold mid-ATL north/cool SE 2/9/10 (10 mb winds prior to this dropped to +2 m/s 1/29/10): very cold SE mid Feb-early Mar; cold Mid-Atl mid to late Feb 1/2/19: cold mid-Atl south mid to late Jan -So, ~half of Ninos since 1958 had a major SSW per ERA by mid Feb. vs 40% of others. -So, for the 11 that had one, all (100%) had BN temps Mid-Atl south dominating for a 3-7 week period starting 1-3 weeks after the major SSW date. In the NE US, 8 of 11 (73%) had BN and others were NN. Conclusion: Due to unanimous agreement of the 11 Nino cases: if a major SSW actually occurs in early Jan, I’ll be expecting a 3-7 week period of E US BN domination, with highest confidence mid-Atl south, starting mid or late Jan and ending anywhere from early Feb through early Mar. If instead one occurs in mid Jan, push these dates out 1-2 weeks. So, most likely period of cold due to major SSW in early to mid Jan would be late Jan-early Feb. It is possible that it will already be cold during or before any major SSW. I’m talking about aftereffects from the SSW, itself. https://en.m.wikipedia.org/wiki/Sudden_stratospheric_warming

OHC looked to have topped at least for now:

Today’s ext GEFS has this at 10 mb as of Jan 2, which looks like the kind of Siberian map you often see preceding a major SSW: the warmest of that is -18C, which is well above normal. That warmth then rotates N around the SPV toward the Arctic over the subsequent few days. The EPS has a good number of members with a major SSW in early Jan that appear to be associated with this same warming. So, these two ensembles are suggesting to look toward early Jan for the first good opportunity for a major SSW. This GEFS run also has a cold E US/+PNA and developing high latitude blocking the first week of Jan. By then, the MJO appears to be headed toward weak 1-2-3, which would be cold supportive. So, regardless of how mild parts of mid to late Dec end up in portions of the E US, Jan would appear to be a whole other ballgame:

Today’s Euro Weeklies SPV runs are similar to yesterday in that they don’t have any new can kicking though they maintain the Dec can kicking of the prior week of runs with only a moderately weak SPV then. A week ago the Dec SPV was significantly weaker. We need to see whether the can kicking looks like it will spread into Jan. But in Jan, today’s maintains a very weak SPV with a similar ~45-50% of members having a major SSW 1/3-22. I count ~16% (vs ~18% yest) that are sub -15, which would be a new record low for early to mid Jan. (The ~10% sub -20 and 2% sub -25 are same as yesterday.) It looks like the first clump is during 1/5-9 (from warming that really gets going in Siberia ~12/28) with a 2nd more spread out grouping 1/12-20. So, once the non-extended models reach the last few days of Dec, it will be quite telling about this first clump. Thus, we’ll start to know much more about the likelihood of that early clump being a real deal mid next week and learn more late next week. Jan 11th EPS mean: still very weak 12/8 run: 15 m/s 12/7 run: 14 m/s 12/6 run: 12 m/s 12/5 run: 17 m/s 12/4 run: 14 m/s 12/3 run: 15 m/s 12/2 run: 15 m/s 12/1 run: 18 m/s 11/30 run: 23 m/s 11/29 run: 23 m/s Check out this 10 mb temp anom and geopotential ht map for 1/8-15. Note the quite displaced mean SPV well S of the N pole at 70N and the high over S AK:

This GEFS PNA forecast tells me that Dec is likely to end up with a +PNA. Should that be the case, that would mean that every month Jun-Dec will have had a +PNA. Since 1950, the only other year with a PNA>0 for all of those months was 2009: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.pna.monthly.b5001.current.ascii.table

The latest AAM forecast (CFS ens) is dominated for the next month by a pretty robust +GLAAM, which is typically associated with El Niño:

The latest EPS extended (bc) MJO forecast is quite encouraging if you want the best chance for BN cold to dominate the E US, especially mid-Atlantic south, late month into Jan from an MJO perspective because it shows weak MJO: Keeping this EPS weak MJO forecast in mind, look at the amplitude of the MJO when there were E US cold events during DJF: almost entirely weak

How do you explain the following from the link below? This leads us to the third aspect of the convection– SST relationship, namely the reduction in convective activity above SSTs of around 30C. As documented by Waliser (1996), these warmest SSTs often occur within the Pacific warm pool region or the Indian Ocean, with timescales of weeks to a few months, and are termed SST ‘‘hot spots’’ or ‘‘warm anomalies.’’ These regions of warmest SST are often free from convection. The crucial point that we have attempted to add to the debate is that current theories on their own do not explain the reduc- tion in convective activity with SSTs greater than 30C. https://journals.ametsoc.org/downloadpdf/journals/clim/14/5/1520-0442_2001_014_0633_otrbtc_2.0.co_2.pdf

Today’s EPS is once again not as weak in late Dec as the prior run. This is the first run without a major SSW member in Dec. But it still has ~45-50 members with a Jan major, similar to yesterday. There are ~18% of members that go sub -15, which would be a new record low for the entire late Dec through mid Jan period. Yesterday, there were 19% that were sub -15. There are 10% sub -20 and 2% sub -25. Jan 11th EPS mean: 12/7 run: 14 m/s 12/6 run: 12 m/s 12/5 run: 17 m/s 12/4 run: 14 m/s 12/3 run: 15 m/s 12/2 run: 15 m/s 12/1 run: 18 m/s 11/30 run: 23 m/s 11/29 run: 23 m/s So, despite mid to late Dec can-kicking over the last week or so, no can kicking yet for around Jan 11th. I’ll be watching to see if early to mid Jan holds in future runs or if the can kicking spreads into Jan: Compare this to the 11/28 run to see how much weaker was Dec on the old run though Jan 5th-12th is weaker on the new run:

Why is +30C a sort of magical SST? From a wx physics standpoint, why is that SST so important? Why not a different SST?

Does +30C still have the same convective significance that it had when the globe was cooler? Let’s say way on down the road that due to AGW that the entire area of, say, 30N to 30S goes +30C+. Would 30C still have as much significance? Wouldn’t the key convection producing SST be higher then? Again, I’m thinking RONI style.

1. I’m not sure what Brad’s thinking is, but I’m suspecting he prefers to keep his area limited to the tropics in deference to the ENSO regions being limited to equatorial. Actually, he goes much wider than the 5N to 5S of ENSO and uses 15N to 15S for his N of Australia area. I recall your area going much further north (to ~30N). Are you sure you should be going so far N of the tropics? Isn’t the tropical area the most important? For that matter, isn’t the equatorial the most important? 2. I realize the record Nov SST warmth that you refer to. But the globe, overall, has been at its warmest much of this year by a significant margin with many other areas at record highs during much of the year. So, on a relative basis (a la the Roni way of thinking), is it really that big a deal that the area you referred to has record warmth? Why wouldn’t other record warm regions balance this out?

The WCS PDO has risen ~0.25 the last 3 days to -0.76 (NOAA PDO probably in/near the -1.3 to -1.6 range):

Keep in mind that this Dec 7th warming has been well modeled for awhile and I assume you realize this is not anything close to a major SSW, which I figure you know requires the mean 60N winds at 10mb to reverse/drop to <0. As one can see on the EPS run below, the 10 mb wind is still way up at ~+30 m/s as of 12/7. So, the current warming is at best considered a “minor” warming. Per this EPS, the first chance for an actual major SSW isn't for another 3 weeks with the best chance not til January. That’s when the real deal may come:

I agree that phases 4-7 have tended to be underestimated for the last few years due largely to the tropical warm WPac per met. Brad Harvey. As I’ve said, he looks at the tropical WPac area N of Australia. That area actually remains cooler than it has been since 2015 and significantly cooler than 2021-3. But what’s happened over the last 7 days? Have the forecasted phases 4-7 strengthened? A. 1) GEFS (bc) run from 11/30: 2) GEFS (bc) run from today: So, today’s GEFS is actually slightly weaker in 4 and significantly weaker in 5-7. ——————————————— B. 1) EPS (bc) run from 11/30: 2) EPS (bc) run from today: So, today’s EPS unlike GEFS is a bit stronger in 4/5 and the first part of 6 vs the 11/30 run. However, it then curls back into the COD beyond where the 11/30 run ended. So, it is a wash over the last week between the changes of the two models. But note that neither of today’s models has it strong at the end with GEFS just outside the COD in 8 and EPS weak inside the COD of 7. Hopefully, the models won’t trend stronger then and that the actual trek into 8/1/2/3 will end up weak. That’s because weak MJO would mean a much better shot at cold late month into Jan vs mod to strong MJO per this diagram of DJF MJO for E US cold shots:

Yeah, per last few extended GEFS and Euro Weeklies, the chance for a major SSW (say when 10 mb winds actually go <0) in late Dec is quite low as of now. The Euro has pulled back substantially on late Dec chances vs earlier runs. But just a few days into Jan, the chances pick up substantially meaning the 2nd week of your two week window has a far greater chance than your 1st week. The EPS is showing right now the best chances for 10 mb winds to first go <0 Jan 2nd-20th. The GEFS suggests best chances Jan 4th or later. Of course, getting one at all is still far from certain. But the signals are there and are probably about as strong as they’re going to be on models still this far (3.5+ weeks) out.

Absolutely awesome and as weak an SPV as on any Euro Weeklies run yet in early Jan! Still, we need to always make sure there’s no can kicking/mirage effect. There’s been some of that in mid to late Dec with not as weak a SPV vs earlier runs. OTOH, for now, I’m not seeing slippage for ~Jan 11th potential, which is where the greatest potential is currently centered. This run appears to have ~~50% of the members with a major SSW between 12/27 and 1/20! The mean EPS gets as low as a mere 12 m/s on Jan 11th vs a climo normal of 33 then! I’ll compare the Jan 11th mean to prior runs to see if there’s can kicking then: today’s run (12/6): 12 m/s 12/5 run: 17 m/s 12/4 run: 14 m/s 12/3 run: 15 m/s 12/2 run: 15 m/s 12/1 run: 18 m/s 11/30 run: 23 m/s 11/29 run: 23 m/s So, no slippage and if anything the opposite with the 12 m/s the weakest yet for Jan 11th. I count 19% that dip to the extreme level of sub -15, which would be near a record low for the entire 12/27-1/20 period. There are 9% that drop to -20, 8% to sub -25, and 5% that go sub -30. Combine that with favorable weak MJO and there would appear to be so much potential for January in the E US, especially mid-Atlantic south:

I was curious and decided to do a Google search to see if I could find any study of the relationship of MJO amplitude and E US temperatures and this is what I found: https://scholarsarchive.library.albany.edu/cgi/viewcontent.cgi?article=1007&context=honorscollege_daes It backs up what I've been saying about weak MJO (including inside COD) as opposed to strong MJO tending to be supportive of cold anomalies in the E US! That's why I'm hopeful for a much colder outcome late Dec onward than 2015-6 and many other winters. Figure 13 (shown just below) in this study suggests that cold anomaly events in the eastern U.S. tend to have weak (amplitude <1) RMM signals. But this includes ALL seasons. All but one of the 17 strong MJO phase 7, 8, 1, and 2 events seen in figure 13 actually occurred OUTSIDE of winter as you'll see in figure 14 shown further down. Figure 14 below is the same except just for DJF. In this, I count a total of 47 cold E US events. A whopping 85% (40) of the cold DJF events had the MJO either just outside, on, or within the COD! A mere one of the 47 (in phase 7) had strong MJO! If you want a cold E US period in winter, your best bet by far is if the MJO is near or inside the COD, which is where model consensus says we're headed. A picture is worth a thousand words: .

Not only Dec, but the entire DJF of 2015-6 was dominated by much stronger MJO than is being suggested this time at least from mid Dec into Jan. Stronger MJO generally translates to a warmer E US. Many of the coldest spells during El Niño have occurred during weak MJO, especially left side. I posted/reposted 15 occurrences with MJO/temps at NYC/ATL in an earlier post to back up my idea. From this point forward, there were only ~10 days of winter near or within COD MJO during 2015-6, with most of that Jan 18-25. The sole big snow of 2015-6 was on Jan 23rd, which was smack dab in the middle of that weak MJO when the MJO was inside the COD phase 2 (red line): In stark contrast to the stronger MJO of 2015-6, the following 2 week progs have a weak phase 8 MJO on Dec 20th with extended model progs suggesting it will remain weak and slowly traverse 8/1/2 going into Jan: 1) GEFS: very slow move in weak MJO 8 at end 2) EPS: slow move in weak MJO 8 at end