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Mid to Long Range Discussion ~ 2023


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 Today's update vs yesterday on the 5 indicators I've been following with first 3 being 0Z GEFS 2 week based:

1. PNA: less + with it now dropping to neutral ~1/7 before slowly rising to ~+0.3 at end of week 2 (vs +0.6 yesterday)

2. AO: slightly + on/near 1/7 vs previously having been - through entire run a few days ago but then still goes back to solidly - (sub -1) by the end of week 2; strongly -AO Dec analogs do favor sub -1 Jan AO overall (more on that in another post)

3. NAO: strong + week 1 but now drops to ~0 by end of week 2 vs  +0.5 yesterday

4. MJO: still progged to be in a supportive position to allow for cold to dominate once into mid January with very slow moving low amp in/near phase 8

5. EPS: 0Z little changed with weak to borderline moderate +PNA after day 10

Summary vs yesterday from SE cold preferring standpoint (I know some prefer warm):

Worse: PNA overall; AO for week 1

Same: AO late week 2, MJO, EPS

Better: NAO


Conclusion: probably no return to cold domination through next 10 days but significant drop in NAO to neutral by day 14 (first time in many days showing this) along with solid -AO, beautiful looking MJO, and back up to a weak +PNA by then tells me that the potential remains for mid to late January to be when cold domination returns. Remember that mid January is still a virtual eternity away in terms of model forecasting abilities.


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 The 12Z EPS is a bit warmer through early week 2 than prior runs and has a mild SE through 1/13 overall in the means. However, it then quickly evolves to much colder with actual BN mean by 1/14-5 thanks to the strongest +PNA late in any EPS run since the runs from 12/27. IF this were to end up real this time (keep in mind we're talking way out in the unreliable late week 2 and that the BN/solid +PNA late in the 12/27 runs (for 12/9-11) has since changed to AN) and when considering my post above with progged favorable AO/MJO along with NAO finally dropping back to 0, mid January and potentially beyond would very likely be much colder than the first 12 days of the month. Keep in mind that the very strong December-AO has a memory of sorts per analogs and that mid to late Jan being dominated by a strong -AO is a distinct possibility.

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1 hour ago, WinstonSalemArlington said:



 This is mainly a rehash of old news for the SE with it showing a torch for 1/1-5 followed by downs and ups into the first half of week 2 with a lean toward AN. But it then shows a gradual transition to BN by the end of week 2 and the start of week 3. This is fully in line with recent days' expectations/model consensus. By the way, my take on RonH is that he's pretty objective in his Twitter posts with him mainly sticking to objective wx model output, whether warm, cold, or whatever from day to day.

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 This shows 850 mb temperature anomalies for the entire 12Z EPS. It shows at 850 mb (5K foot elevation) in the SE US a torch 1/1-4, a cooldown to BN 1/5-6, a warmup to AN 1/8-12, and then a cooldown to BN 1/14-5 in most of the US due mainly to a combo of the strengthening +PNA/-AO. Keep in mind these are 850s rather than ground temperatures. Ground temperature changes often lag 850 changes. Also, low level features like CAD are often not reflected well up at 850 mb:


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 The above two posts make it sound like AN temps will dominate the SE through the somewhat foreseeable future (say 15 days). If I read them and didn't look at any data, I'd be inclined to think that. Also, if I saw it that way, I wouldn't be afraid to suggest similarly as my style is to post with objectivity as a prime goal. But I don't see it that way.

 In a nutshell, the current torch will end abruptly all areas by 1/5 followed by a couple of chilly days. There will likely be a return to AN a few days later that is expected to last no more than 5 days. After that, the prospects for significantly colder starting ~1/13-4 are coming into better focus.

 Below is a link to the entire run of 12Z EPS 850 mb temperatures, which illustrate all of this quite well. The chance of a return to a solid +PNA by midmonth looks as high on this run as any in the last 5 days.

 For those preferring cold domination, the hope is that the EPS won't backtrack like it did for the period near 1/9-10 about five days ago. Based on midmonth GEFS progs of the combo of strong -AO (nearing -2), which is supported by the 3rd strongest Dec -AO on record since a strong Dec -AO tends to have a memory; a drop in NAO toward zero; and a favorable MJO for +PNA/cold SE, I feel that the EPS is probably on the right track this time as opposed to my saying this just based on my desire:


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 Since yesterday, the EPS (along with the GEFS) has warmed in the SE/much of the E US near midmonth and is now suggesting that the midmonth cooling may not last more than a few days or be as strong with the +PNA then quickly dropping back. Today's 0Z day 14 GEFS PNA forecast took a hit from yesterday's ~+0.5 to today's ~0. That's a drastic change for just one day.

 The day 14 GEFS NAO rose from yesterday's ~0 to today's ~+0.2. Though the AO still looks solidly negative and the strong Dec -AO favors a sub -1 AO this month, it doesn't look as strongly negative late in today's GEFS run as yesterday's nearing -2. Today's isn't much lower than -1 along with most members then rising. The MJO does still look favorable for cold with a phase 8 though with a little higher amp. (I prefer low amp.)

 Yesterday I said this:

"For those preferring cold domination, the hope is that the EPS won't backtrack like it did for the period near 1/9-10 about five days ago."

 Unfortunately for cold lovers, today's 0Z EPS backtracked somewhat for midmonth though it is just one run. We'll see whether or not the 12Z EPS agrees.

 The following link from a knowledgeable NYC forum poster "bluewave" shows very well how much the EPS and GEFS (especially the EPS) have backtracked from a return to cold/solid +PNA for January 10th on the 0Z/6Z 12/26 runs (what I was referring to yesterday) to a warm E US for January 10th on today's 0Z runs due to underestimating the strength of the Pacific jet:



 I mentioned last week that the Indonesian waters/MC are near record highs (similar to last several years) and that this along with La Niña would likely mean periods favoring the SE ridge. I wonder if this is the main reason for underestimating the Pac jet.

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 For those like myself who want the progged mid January chill to be the start of a long period of cold domination, the 0Z EPS and now even more emphatically the 12Z EPS is saying the chances of that are dropping. Whereas the 12Z EPS looks a bit colder than the 0Z toward midmonth with the cold period thanks to a decent +PNA, it is also showing it to be only a ~3 day long chilly period as the +PNA quickly transitions to a zonal/strong Pacific jet/warming pattern to at least near normal with no new cold then in sight. That progged quick end to the chill is still two weeks out and can obviously change drastically. However, today's ensemble consensus changes are clearly moving away from the possibility of the start of an extensive, long duration cold pattern at midmonth. Based on how often model consensus has been doing this kind of thing since late November outside of the big cold of late December, this isn't at all what I wanted to see.


Edit: I should reiterate it does look pretty cold on the 12Z EPS for ~3 days near midmonth. That would possibly be a period to look for the chance of snow from an off the coast storm for mainly NC north just taking the run at face value. The run is showing a pretty good number of members with off the coast storms centered at the start of this cold period late 1/13 to early 1/14. If there is a low there then, would enough cold air get entrained before the moisture is gone?

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6 hours ago, Grayman said:

Thanks for all the input. I punted until February anyway because you can’t just waste a late December pattern like that and put up a goose egg. I enjoy your fact based posting . Happy New Year. February will save the board lol

Only one problem .....  Februarys in a La Nina year typically mean torch city. So, if you are going to punt all of January, might as well punt February too....... Oh, and just food for thought, punting the entire winter on the second day of January is not a wise move. We are all sore about the bitter cold in December with nothing to show for it, however there will still be more chances.

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We missed the chance with the prolonged cold.  Unless the pattern shifts, we are going to need to rely on great timing with a quick cold blast and a low moving in a favorable path.  That's typically what we end up getting anyway.  Snow in the morning and melted by the afternoon.  

The ensembles do show some members picking up on a system around the 15th.  

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7 hours ago, CAD_Wedge_NC said:

Only one problem .....  Februarys in a La Nina year typically mean torch city. So, if you are going to punt all of January, might as well punt February too....... Oh, and just food for thought, punting the entire winter on the second day of January is not a wise move. We are all sore about the bitter cold in December with nothing to show for it, however there will still be more chances.

 I looked at February temperature anomalies of 34 La Niña Febs to see what are the chances based on the last 140+ years for a torch (using respective 30 year averages) in the SE using ATL stats as representative:

1887: +8

1890: +10

1893: +1

1894: 0 (major snow)

1904: -3

1909: +4

1910: -3

1911: +5

1917: -2

1925: +5

1934: -6 (major snow)

1939: +4

1943: +1

1950: +5

1955: +2

1956: +5

1971: -1

1974: +1

1975: +2

1976: +7

1985: -1

1989: +3

1996: -1

1999: +1

2000: +3

2001: +2

2006: -4

2008: 0

2009: -1

2011: +2

2012: +3

2018: +9

2021: 0

2022: +3

 If I use +5 as minimum required for torch, I count 8 torches (MA) (24%), which is a lot. There are also 10 A (+2 to +4)(29%). So, a whopping 18 of 34 (53%) are A to MA. Normally, A to MA would comprise no more than ~35-40%.

 There are 11 near  N (+1 to -1)( 32%). I count only 4 B (-2 to -4)(12%) and just 1 MB (-5 or colder)(3%). But that still means 47% (nearly half) were near normal or colder. So, whereas we often read about the assumption (likelihood) of a mild Feb in a La Niña, the reality is that that chance is only a little over 50% and the average of the 34 Niña Febs was only +2 at ATL. That's because the largest # in any category is actually near normal. In fairness though, the chance of cold is much lower than mild.

Conclusion: During any La Niña, there is a high chance that Feb won't be cold. However, there actually isn't a high chance but rather more or less only a coin flip type chance that Feb will be mild.

 ENSO data:

 Pre 1950 from Eric Webb:


1950+ from NOAA:



ATL temperature data:


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Wish I could say I'm surprised the models have backtracked on cold but that seems to be the theme this year (other than the 3 day cold outbreak) The Pacific is still raging. California is getting pounded by storm after storm. We (foothills of NC) haven't had a decent snow in February since 2015. It just doesn't happen much anymore. 

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