GaWx

Regarding cold periods during DJF in the E US, a large portion of them occurred during weak MJO per this: https://scholarsarchive.library.albany.edu/cgi/viewcontent.cgi?article=1007&context=honorscollege_daes

Note that the coldest and snowiest part of the month was Jan 15-31, when the MJO was weak (near or inside the circle). Jan 1-14 averaged near normal temps whereas Jan 15-31 averaged B to MB. This was similar to the case in the SE US, where Jan 1-14 averaged A with temps before being MB Jan 15-31 along with above average snow.

From Judah Cohen’s blog: “A larger PV disruption is more likely in early January that has the potential to reverse the overall mild pattern for the NH to a much colder one. Hard to provide details just yet and I expect a lot of volatility in the forecasts so buckle up.” “It is of my opinion, much of the winter will likely hinge on the nature of this SSW that is predicted to begin the last week of December.” https://www.aer.com/science-research/climate-weather/arctic-oscillation/ ————————- Interesting update from Judah! Keep in mind that major SSWs are often though not always accompanied by mildness in the E US before, during, and afterward prior to it later getting colder as their influence moves down into the troposphere and often results in a -AO/-NAO to then dominate. It often takes 1-3 weeks (avg ~2 weeks) for them to get deep down into the troposphere. It can of course already be cold when they occur, but that would obviously be due to other factors like a favorable MJO, for example.

Today’s 0Z extended GEFS mean, like recent runs, suggests a significant weakening of the SPV and warming of the Arctic in early Jan. But will there actually be a major SSW/reversal of 60N winds? That’s the big question:

Today’s Euro Weeklies are about as weak as any run yet for the last few days of Dec/early Jan. Total major SSWs are ~~50%. The highest concentration of major SSWs occur Jan 2-9 (~25% of members), which is supported by E QBO climo. (The extreme SSWs throughout Jan increased with ~17% total sub -15, ~15% sub -20, 5% sub -25, and 2% sub -30.): 10 mb temp anoms/hts 1/1-8: Also, Jan 8-15 cooled back almost to as cold as the run from 3 days ago. But no football spiking from me!

Yeah, this trend isn’t at all what I wanted to see. This means that the NOAA PDO is quite possibly back down to ~~-2.0. My hope is still for a sharp enough reversal soon to allow for a JF PDO to average >-1 in the NOAA table, a doable but unfortunately very tall task as of now. But regardless of the PDO, the good news from an E US cold lovers standpoint is always having the major SSW wild card possibility to shake things up drastically via -AO/-NAO blocking in Jan and/or Feb as it often means a major atmospheric reset. All major SSWs since 1958 during El Niño have had a 3+ week long period of cold domination after 1-3 weeks following them as I’ve posted about. 60% of El Niño winters have had a major SSW. Also, QBO E have had more than QBO W. The best shot at a major SSW during QBO E per analogs is very late Dec to early Jan as per@40/70 Benchmarkand SSW history. If we can get that combined with weak MJO, I’d be pretty excited about potential for E US cold in a good portion of Jan and/or Feb.

1. That’s about to drop to ~+1.9 based on WCS dropping from +2.0 to +1.89 in today’s update. 2. The WCS PDO has been falling sharply in recent days and is -1.35 in the latest, the lowest in two months (NOAA may be back down to ~~-2):

1. It dropped from 48% to 32%, but 32% is still significant. The EPS is at least that high for very late Dec into early Jan. 2.

Why do you feel it us even a toned down version of 1997/2015? At best as it looks now the MEI may get only to ~1/2 the MEI of those two (say, low +1s). The RONI is looking to top at only low end strong vs the ~+2.35 peaks of 1997/2015. So, based on MEI and RONI, should 2023 even resemble those?

Thanks, very interesting stuff! Regarding what I bolded, is this Nino really all that strong when you consider it is only low end strong on a RONI basis and was still only weak on an MEI basis as per the ON of +0.6? Much of this thread's discussion for a long time has been emphasizing that the current Nino is not that strong and not well coupled with the atmosphere.

+GLAAM wouldn’t favor an Aleutian low instead of a GOA low?

Wow, look at how high the CFS is now forecasting GLAAM to go (consistent with strong El Niño influence)! I don’t recall seeing it this high before. But to be fair I haven’t seen all that many of these charts before as I’m only now first following it regularly:

Now I see why you picked those dates. If I looked at the list linked below, which is more up to date (though it still needs 2/16/23 to be added), it even more emphatically backs up your thinking because it shows Dec 31-Jan 9 to be the most concentrated period throughout winter for a major SSW during QBO E since it also includes 1/9/77 and 1/2/2019. So, for E QBO going by ERA, this source has 1/9/77, 1/1/85, 12/31/01, 1/5/04, 1/6/13, and 1/2/19. So, 6 events in just that 10 day period. If W QBO were also to be included, this source has a whopping 9 events within that 10 day period because 1/7/68, 1/2/70, and 1/5/21 would be added. The only other comparable period for all QBO is the 8 events within the 9 day period 2/21-29. https://en.m.wikipedia.org/wiki/Sudden_stratospheric_warming

The strat stuff discussed by Cohen and others is so fascinating! To me, getting a major SSW resets the whole winter playing field. It is like getting a new QB and perhaps even more like getting a whole new team mid-game. Here’s something I found recently: In this, I noticed these things: -QBO: E beat W by a large margin, 22 to 13 -QBO E: 14 displaced vs 8 split -QBO W: 4 displaced vs 9 split -QBO E El Niño: 6 displaced vs 3 split -QBO W El Niño: 2 displaced vs 4 split -Best bet for one is QBO E La Nina followed closely behind by QBO E El Niño -El Nino had 15 from 12 winters (out of total of 20 winters) and La Niña had 13 from 11 winters (out of total of 18 winters), but neutral had only 7 from 7 winters (out of total of 18 winters) -To get two in one winter, you almost always have to have first one by Dec

Mitch, I didn’t say it that way, but you’ve got the general idea. A study was done showing that the vast majority of cold E US events in DJF were when the MJO was weak (near, on, or within COD) as per this: So, whereas I didn’t go as far as to say that weak MJO results in cold in the E US, I did say that the best chance by a good margin from an MJO perspective for it to be cold is if it is weak. That’s what this chart shows. So, whereas it sometimes is mild even during weak MJO, it is difficult for it to be cold when the MJO is strong. So, as a cold lover, I always prefer weak MJO to dominate so as to maximize the chances for cold. Also, I earlier (independently of the study from which came that diagram because I hadn’t yet been made aware of it) posted 15 periods during El Niño that had weak MJO, mainly left side, that were cold dominated in the E US, especially SE.

1. Today’s Euro Weeklies are still weak with the SPV in late Dec and especially early to mid Jan. The highest concentration of members with a major SSW is during Jan 1-12. Whereas the number of members with one dropped some (~~50% today vs ~~60%+ yest), the number of extreme SSW actually rose (~15% sub -15, 10% sub -20, 5% sub -25): 2. Today’s 1/8-15 warmed up a lot since yesterdays cold E US map.

The MEI warmed from +0.3 in SO to +0.6 in NO. That warming is good news as the 10 coldest El Niño winters in the SE US since 1950 had a DJ MEI of +0.5 to +1.5. So, we needed the MEI to warm up and now we’ll need the next two MEIs to maintain this warmup and preferably warm a little more as we reach DJ. The 10 coldest El Niño winters back to 1951-2 were 1957-8, 1963-4, 1965-6, 1968-9, 1969-70, 1976-7, 1977-8, 2002-3, 2009-10, and 2014-5. Per Webb’s table these were the rounded DJ MEIs: +1.5, +0.9, +1.3, +1.2, +0.8, +0.8, +0.7, +1.0, +1.1, and +0.5. So, a range of +0.5 to +1.5 for the DJ MEI with a mean of +0.95 and a median of +0.95. So, sweet spot near +1.0 for the 10 coldest in the SE. The 6 coldest were 1957-8, 1963-4, 1969-70, 1976-7, 1977-8, and 2009-10. MEIs for these 6: +1.5, +0.9, +0.8, +0.8, +0.7, and +1.1. So, range of +0.7 to +1.5 with mean of +1.0 and median of +0.85. El Niño Winters with DJ MEI within +0.5 to +1.5 that weren’t cold: -1958-9: +0.7 cool -1979-80: +0.7 NN -1986-7: +1.1 NN -1987-8: +0.9 cool -1991-2: +1.5 mild -1994-5: +0.9 NN -2006-7: +0.8 NN So, when DJ MEI was within +0.5 to +1.5 during El Niño, the SE had a cold winter 10 times, cool twice, NN 4 times, and mild once. When the DJ MEI was outside that range during El Niño (7 times with 4 higher and 3 lower), the SE had no cold winters. For the SE if we could get a DJ MEI to within the +0.6 to +1.2 range, a <-0.50 DJF AO, and a <+0.25 NAO, I’d bet heavily on a 2F or more BN DJF. —————- MEI: https://psl.noaa.gov/enso/mei/

Bullseye! The MEI warmed from +0.3 in SO to +0.6 in NO. That warming is good news as the 10 coldest El Niño winters (in the SE US, TN, and at least nearby areas to the north) had a DJ MEI of +0.5 to +1.5. So, we needed the MEI to warm up and now we’ll need the next two MEIs to maintain this warmup and preferably warm a little more. The 10 coldest El Niño winters back to 1951-2 centered on the SE and nearby were 1957-8, 1963-4, 1965-6, 1968-9, 1969-70, 1976-7, 1977-8, 2002-3, 2009-10, and 2014-5. Per Webb’s table these were the rounded DJ MEIs: +1.5, +0.9, +1.3, +1.2, +0.8, +0.8, +0.7, +1.0, +1.1, and +0.5. So, range of +0.5 to +1.5 for the DJ MEI with a mean of +0.95 and a median of +0.95. So, sweet spot near +1.0 for the 10 coldest in the SE and nearby. The NE’s list is probably not too dissimilar. El Niño SE winters with DJ MEI within +0.5 to +1.5 that weren’t cold: -1958-9: +0.7 cool -1979-80: +0.7 NN -1986-7: +1.1 NN -1987-8: +0.9 cool -1991-2: +1.5 mild -1994-5: +0.9 NN -2006-7: +0.8 NN So, when DJ MEI was within +0.5 to +1.5 during El Niño, the SE had a cold winter 10 times, cool twice, NN 4 times, and mild once. When the DJ MEI was outside that range during El Niño (7 times with 4 higher and 3 lower) the SE had no cold winters. All of this likely largely applies to the NE, too. Actually, 1958-9 was downright cold there vs just cool in the SE. —————- MEI: https://psl.noaa.gov/enso/mei/

Today’s released weekly SST anomalies (which cover last week) show a dramatic cooling in 1+2 to only +1.3 from +2.1 the prior week! Nino 3 remained at +2.0 while Nino 3+4 dropped slightly from +2.0 to +1.9. Nino 4 dropped notably from +1.7 to +1.4. So, the bookends dropped while the middle two regions stayed about the same and have the warmest anomalies. This makes it currently a cross between EP and CP. With Nino 1+2 so much cooler now and Nino 4 still unusually warm for it, it is arguably a little more CP than EP. Regarding the current RONI, it is likely hanging only near low end strong (~+1.5 to +1.6). So, we currently based on RONI appear to have the equivalent of a low end strong CP/EP El Niño and nothing close to a super strength EP.

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