GaWx

1. Even though I replied to your post, I didn’t intend for it to be just for you. Temperatures are an important aspect of winter to monitor on their own, especially during winter. Although I’m not yet expecting super cold, the fact that it’s possible in ~10 days is intriguing. Widespread cold on its own can have at least as much (if not more in some cases) impact as a snowstorm. Plus it could set the table for a followup winter storm in more ways than one though that’s beside the point. 2. Last Dec MJO: I’m pointing out similarities for those who may find it interesting. You don’t care, but others might. There are a lot of members and guests that read these. I love to look at both similarities and differences of various factors when looking back in wx history.

Although likely too cold, the even colder 12Z CMC is somewhat similar with very cold air moving into the SE on 1/17, which would likely lead to the coldest of the winter to this point. Similar to last winter’s coldest around Christmas, this appears like it would be during a moderate to strong MC phase of the MJO interestingly enough. The strong -EPO/-AO/-NAO combo doing its thing.

In my area we quite possibly will have the coldest first half of January since 2018 with right at normal.

The 0Z 1/7/24 EPS mean has maintained the Jan 11-18 period of near or sub -150 (-1.5) EPO that was on this 0Z 1/4/24 run. An 8+ day long period of -150 or lower has occurred about once every two winters on average since 1948 with no winter having more than two of them. The 0Z 1/7/24 EPS run is implying that the low of this period would probably be sub -300. https://downloads.psl.noaa.gov/Public/map/teleconnections/epo.reanalysis.t10trunc.1948-present.txt

Thank you. So, the 0Z 1/7/24 EPS mean has maintained the Jan 11-18 period of near or sub -150 (-1.5) that was on the 0Z 1/4/24 run. An 8+ day long period of -150 or lower has occurred about once every two winters on average since 1948 with no winter having more than two of them. This EPS run is implying that the low of this period would probably be sub -300. https://downloads.psl.noaa.gov/Public/map/teleconnections/epo.reanalysis.t10trunc.1948-present.txt

Does anyone have the latest EPO forecast from the EPS or any model? TIA

Thank you!

I follow you. I just wanted to make sure that y’all were aware of the fresh snowcover bias. Regarding the CMC, it overall has a colder bias than the GFS. I don’t mean just over snowcover. I mean in general. Even if it doesn’t get as cold as the 18Z GFS but it still gets very cold, that would mean quite possibly the second winter in a row with the coldest of the season when the MJO was in a moderate to strong MC phase.

I saw the insane cold on the 18Z GFS. I recommend taking the GFS with a huge grain over fresh snow-cover because it has had a strong cold bias over modeled fresh snow-cover for at least several years: https://dtcenter.org/sites/default/files/events/2020/4-patel-ronak.pdf Cold is coming, no doubt. But the insane cold that far south on the 18Z GFS isn’t realistic. I believe the Euro may also have this bias (at least it did a few years ago), but I don’t think to this degree.

So, the 0Z 1/4 EPS was forecasting a strong -EPO for mid Jan, the period I’m analyzing for SE winter storm chances. That would be a pretty big deal if it verifies. 80% of the moderate right side MJO with widespread SE mod to heavy wintry precip had a strong -EPO. This shows an 8 straight day period of sub -150. How often does that occur in any one winter? There have been 40 instances since 1948 or about one every other winter on average. No winter has had more than two. So, if that EPS is right, it would be a pretty big deal, especially when combined with a -AO. But this is all looking to go against a robust MC MJO. The lengthy strong EPO strings fully in Jan were (temps/wintry precip are for SE): 1/10-18/1957: cold (-PNA, +AO, neut NAO) 1/18-29/1961: very cold/wintry (+PNA, -AO, neut NAO) 1/15-22/1962: cold/wintry (-PNA, +AO, neut NAO) 1/9-31/1963: very cold (+PNA, -AO, -NAO) 1/17-26/1969*: slightly AN (-PNA, -AO, -NAO) 1/1-11/1974: mild (-PNA, +AO, neut NAO) 1/1-9/1979: very cold to cool (MJO mod 7-6) (-PNA, -AO, neut NAO) 1/20-28/1991: cold/wintry (MJO mod 3-4) (neut PNA, +AO, neut NAO) 1/4-14/1993: mild (MJO strong 8-1-2) (-PNA, +AO, +NAO) 1/1-9/2005*: warm (MJO mod 4-5) (-PNA, +AO, +NAO) 1/14-23/2009: very cold (MJO strong to mod 7-8-1)(+PNA, +AO, +NAO) 1/20-28/2014: very cold/wintry (MJO mod 6-7) (+PNA, -AO, +NAO) 1/1-11/2015*: cold (MJO mod to strong 5-6) (neut PNA, +AO, +NAO) 1/1-8/2017: cold/wintry (MJO rt side COD) (-PNA, +AO, neut NAO) * = El Nino Analysis: - 10 of 14 were cold - 5 of 14 were wintry - MJO: all over the map - +PNA: all 4 very cold - All mild to warm had -PNA but half the -PNAs cold - Twice as many -PNA as +PNA - -AO averaged colder (4 of 5 cold) than the more common +AO but 2/3 of +AO still cold - Only 2 of 14 -NAO and one of those mild - 6 of 7 neut NAO and 3 of 5 +NAO cold Conclusions for upcoming -EPO: - Having a -AO will favor cold - Progged to have weaker -PNA than the 8 -PNAs listed. Thus, I don’t think it would prevent cold though it likely would prevent extreme cold. - Better chance for cold without than with widespread significant wintry precip but that’s no surprise since it is the SE. But 5 of 14 (36%) being wintry beats the odds of most 8-12 day periods in Jan. - And cold looking very likely per EPS. All 5 wintry cases were cold. That’s 5 of 11 (45%) cold cases being wintry. That’s high for the SE for an 8-12 day period in Jan! -Weak -PNA would likely neither hurt nor enhance the wintry chance. -If MJO is strong like what GEFS has, that may hurt wintry chance. Hoping MJO more like EPS. -Oddly enough, -AO/-NAO surprisingly didn’t seem to help with wintry when considering these 14 cases fwiw though I’d still rather have them. Anyone have the latest EPS (or any model) EPO forecast?

1. But if ONI peak were to end up +2.00+, why wouldn’t it be known as a low end super? I don’t follow you. 2. Now regarding RONI, which many have been saying is more relevant to sensible wx, it looks to most likely peak in only low end strong.

Today’s OISST dropped to +1.87, lowest since 11/16. But that’s a huge drop of 0.2 in just 2 days. Often there’s a correction soon after a sharp move. Regardless, OISST would likely need to average under +1.80 Jan 7-31 to prevent a super ONI peak. What are the chances for that? I’m still saying pretty low but it obviously is doable.

-That’s not Nov but rather it’s OND, which was +1.94 (rounds to +1.9). -Nov, itself, was actually +2.02. Dec was +2.07: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/detrend.nino34.ascii.txt -That means that Jan ERSST only needs to end up at +1.91 to allow NDJ to average +2.00. And you don’t need three months of +2.00+. Just the average of the 3. Currently, Jan 1-5 is ~+2.15 for ERSST, based on it having averaged 0.08 warmer than OISST over the last 5 months. For 11/1/23-1/5/24, ERSST is ~+2.05. To bring down ERSST to under +2.00 for 11/1/23-1/31/24, ERSST would need to be +1.87 or cooler for 1/6-31, which equates to ~+1.80 or cooler for OISST for 1/6-31. So, do folks think that OISST will average <+1.80 for 1/6-31? That’s about what it will take to prevent a super ONI peak. OISST hasn’t had a single day under 1.80 since Nov 16. Opinions? Yesterday it was at +1.94 but that was only after a good drop. I think the odds are pretty low, but we’ll see. That’s why I’m favoring that we get a super peak as of now.

Absent a steep fall in 3.4 the rest of the month, there’’d actually be a very good chance for a super as unrounded NDJ ONI (ERSST, which has been running slightly warmer than OISST for several months) would be +2.00+. ND is ~+2.05.

Followup on my search for a big SE winter storm when MJO was strong on the right: Couldn’t find any when right side strong like GEFS has (amp 2+) but found 3 big and 2 moderate storms when MJO was right side moderate (like EPS has): -1/24/1991: mod SN ATL-CLT; mod phase 4 -3/13/1993: historic SN for many; mod phase 4 -12/18/1996: mod SN ATL-GSP; mod phase 5 -1/9-10/2011: big storm for many; mod phase 5-6 -1/17/2018: big storm for many; mod phase 4 So, the progged MJO is a negative factor as most of us already knew. However, if it would end up moderate like the EPS instead of the GEFS’ strong, history says that there’d be a shot at a moderate to big winter storm over a good portion of the SE should the SE get as cold as the EPS shows (5-10 BN averaged over up to 10 days). Note that 3 of the 5 were during 1/9-24, in/near the progged cold period and near coldest climo though none were during El Niño. How was NAO/AO/PNA/EPO during these 5? 1. NAO range was -0.3 to +1.3. 2. AO range was wide: -3.4 to +2.2 (3 +, 2 -) 3. PNA range VERY narrow: -0.2 to -0.4 4. EPO range -320 to +60 with 4 of 5 strong - So, weak -PNA and strong -EPO prevailed. None had a moderate or stronger -NAO. AO all over the place. Has anyone seen an EPO prog?

The 0Z EPS, which is colder than the GEFS, is the coldest run yet overall for midmonth (1/14+) for the C & E US, including 5-10 BN SE. This includes extreme cold anomalies over the C Plains and a very cold Midwest. It implies two Arctic highs coming down into the Plains feeding cold but not plunging into the SE. This of course doesn’t necessarily mean there would be a widespread significant SE winter storm near or just after this cold period (1/14-21+) as widespread big SE winter storms are pretty infrequent. I’m not even saying I’d bet on it. But if there actually would be a 10+ day period averaging 5-10 BN in the SE during mid to late Jan (at/near the coldest climo means of the year) in El Niño, that would imply an above climo chance for SE wintry precip overall, including a significant winter storm chance. What would be best for snow would be for a very cold high to plunge into the Midwest and then move E near the Ohio Valley instead of into TX/OK because it would allow for the chance for moisture to return while it is still cold. Looking at indices, whereas the progged strong right side MJO isn’t at all favorable, the -NAO/-AO keeps the door open. If I get time, I’ll check to see if I can find a big SE winter storm when the MJO was strong on the right. Is the EPS right or is it too cold? I don’t know the answer.

Today’s GEFS progs of -AO/-NAO aren’t as strong as those of yesterday (which can be seen in the quoted post): 1/5/23 GEFS AO prog: 1/15/23 has 80% >-3 vs 80% <-3 on the 1/4/23 run: 1/5/23 GEFS NAO prog: 1/15/23 has most >-1 vs most <-1 on the 1/4/23 run:

Actually, I think I’m largely in agreement with @so_whats_happening.Wouldn’t it make sense that there always (not just sometimes) is a lag (of however many days, which would vary from case to case) between what happens in the tropics/MJO and what happens in the middle latitudes (E US temperatures for example)? However, my agreement doesn’t mean that I shouldn’t still use those composite maps for concurrent. I think that’s where we disagree. It is tricky. So, for example, if we want to predict E US temperatures during an upcoming phase 8, I’d say going with BN makes sense based on the maps, which show concurrent US temperatures. That’s even though the BN temps were likely a result of a lag from phase 7.

I understand the concept of a lag from the MJO (tropics) to the mid latitudes. That makes perfect sense and thus I’m not disputing it. By the way, how many days is the average lag? But this is tricky imho. Check this out, the link to the MJO/US temperature composites that I look at: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Temperature/ From that link, here are the DJF composites, for example: In the “Information” section linked below that goes along with these composites, it says nothing about lag between these composite maps and the respective phase noted for each map: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Temperature/readme.shtml As I see it, these composites aren’t actually disputing that there is a lag. Rather, they are the after effects of a lag. For example, let’s look at phase 8. The concurrent temperatures average BN in the E US. But in reality, these BN temperatures have to have been a result of a lag from what was earlier initiated in the tropics (an earlier MJO phase) rather than from phase 8, itself. I’m educatedly guessing that this earlier phase is 7 in a large % of cases since the MJO typically rotates counterclockwise. Which phase in a particular case would be dependent on the number of days of the lag for it. If the lag for a particular case is, say, 5 days, we need to see where the MJO was 5 days earlier for that case. Let’s say it was in phase 7 five days earlier. Let’s say it was BN in the E US five days later. Thus it was in reality the phase 7 of five days earlier rather than phase 8, itself, that lead to the BN E US five days later, which happened to be during phase 8. So, as I see it, what resulted in the BN in the E US during phase 8 actually likely originated from what was happening earlier in the tropics during phase 7. So, even though these composites show concurrent E US temps during phase 7 to average AN, that AN is apparently actually a lagged effect from an earlier phase (say phase 6 in many cases). Phase 7, itself, is probably associated with a BN E US but due to lag the BN doesn’t occur til the MJO has moved into phase 8. So, the E US warmth during phase 4/5/6 is likely largely a lagged effect from phase 3/4/5. The E US cold during phase 8/1/2 is likely largely a lagged effect from phase 7/8/1, etc. The extreme cold of 12/23-7/2022, which occurred during phase 5, was likely a lagged effect of phase 4 since it was mainly in phase 4 during 12/8-22/2022.

That sudden increase in members with a major SSW near midmonth is still there on today’s (1/4/23) 0Z EPS (just something to follow as it could impact Feb):

The SE may very well not as snow is so unpredictable and there is a mix of factors. However, sometimes such a strong combo of -NAO and -AO will dominate enough to overcome the others. For example, the Jan 9-11, 2011, big winter storm had a moderate MJO phase 5-6 along with a neutral to slightly -PNA. It did have a potent -EPO, which may be in its forecast. Anyone have a GEFS EPO forecast?

Not necessarily. Last winter’s coldest (near Christmas) had a similarly strong MC MJO. Also, Jan 20-31 of 1978 had similar. MJO, just like most indices, tells us what usually happens as opposed to what nearly always happens. I should add that I haven’t seen a GEFS EPO forecast. Anyone see it? I suspect that might be negative, which would be favorable.

The 0Z GEFS is forecasting towards midmonth easily the strongest Jan -NAO since 2011 and 2010. Both of these times, ATL and other areas had measurable snow with 2011 being major in much of the SE US. It is also forecasting a very strong -AO. In addition, it is forecasting a strong MJO phase 4 and moderate -PNA.

The 0Z GEFS is forecasting easily the strongest Jan -NAO since 2011 and 2010: The 0Z GEFS is forecasting a very strong -AO along with it: Along with these, it is forecasting a strong phase 4 MJO and a moderate -PNA.

Some 0Z/6Z models like the 6Z GFS are suggesting a chance for a major SSW near midmonth like yesterday’s 0Z EPS was suddenly doing.