GaWx

 Today’s GEFS is progging ~-1.7 PNA for Dec as a whole. That would be ~5th strongest -PNA since 1950. But what were similarly strong -PNA Dec followed by in Jan since 1984-5 during -ENSO?

1984-5: from -1.6 to +1.6

2008-9: from -1.4 to +0.6

2010-1: from -1.8 to +1.3

2021-2: from -2.6 to +1.0

 All 4 of these Januaries were cold in the E US.

The radiational cooling in much of the SE has been quite impressive the last 4 hours!

 This afternoon’s walk was another pleasant one due to still pretty dry air (dewpoints mid 30s), blue skies, and light winds though it was ~20 warmer (60 vs 40). So, though it was pleasant, it felt better and more invigorating yesterday.

 Natural gas is down still another 3% today making it a total of a whopping 29% just since the high of Dec 4th!

30 minutes ago, wncsnow said:

I don't even have an account on there. 

7 minutes ago, BooneWX said:

You don’t have to. I peak over there to cross check the vibes and today is a hilarious war of words. That’s why I stick here. Everything is measured and while they have some great posters, it’s full of too many folks speaking in absolutes and getting obnoxious when the ball doesn’t roll their way. 
 

I go here to converse, read anything from @Carvers Gapto learn, and head there for my entertainment.

 The two forums are very intertwined between many (probably a majority) of its members also being members and former posters here as well as some currently posting at both (in some cases with different names). I’m sure many read both boards daily.

1 hour ago, BooneWX said:

It is what it is at this point. We won’t be the only ones suffering. Best advice I’ve got is for everyone to take a deep breath at the keyboard, go outside, smell some Christmas trees, golf, fish, get some vitamin d. It’s been a cold 3 weeks and a break won’t be bad. I hope it’s not extended but what can any of us do about it? Jammin January and Fab Feb are just around the corner. 

 For me it wouldn’t be “suffering”. It isn’t anything like, say, bad health/getting sick. “Suffering” is too harsh a word from my standpoint even though it’s not at all what I prefer as I want it colder than normal at any point in the year. The good thing is that it’s my favorite season of the year and warmer than normal in winter is still much colder than, say, below normal in summer. In addition, this warmer period will be following one of the coldest 3 week periods from Thanksgiving through the first 17 or so days of December I’ve ever experienced and easily the coldest since 2010.

 Even if it’s going to be mild for awhile, forecast discussions would still be interesting in the most volatile season of all, winter.

6 minutes ago, 40/70 Benchmark said:

Does anyone have the link to the historical ERA5 10hPa 60N zonal wind data? For some reason my link no longer takes me to it....

Ray,

 If you mean the link to the site that produces the graphs of 10 hPa/60N mean zonal wind back to 1978-9, those could be produced by going in here:

https://acd-ext.gsfc.nasa.gov/Data_services/met/ann_data.html#ncep_clim_stats_nh

7 minutes ago, JenkinsJinkies said:

Also 16-17, 22-23 had no measurable December snow in the DC and Baltimore area airports. Very much not the case this year.

Also, Dec of 2016 had a +WPO and Dec of 2022 had a neutral WPO unlike the -WPO of Dec of 2025 fwiw.

 Our airport had a low of 25 for the 2nd morning in a row. My lowest was likely ~30 vs 26.6 yesterday. But the freeze last night was radiational rather than advective/windy with a much longer duration of ~9 hours.

1 hour ago, 40/70 Benchmark said:

All 6 of those seasons finished with a mean DM -WPO, so this season should, too....though we could have a month or two average +WPO, as was the case in 1990. Looks like I am going to be off on the WPO again...it's so tough to forecast. At least I didn't go strongly positive....

57 minutes ago, EastonSN+ said:

3 good and 3 bad winters snowfall wise. Nice even split.

 Thanks. That’s based on my 1st list, which is of those Decembers that had 1+ days dipping lower than -3.48. But those Decembers didn’t necessarily have a solid -WPO dominating through the entire month. One of those Decembers, 1996, actually averaged a +WPO overall. Also, 1983 and 1977 didn’t average a negative enough WPO. And there were a bunch of Decs left out of that 1st list that had a very -WPO with it dominating throughout but that didn’t have at least one day dip below -3.48 like 2013, 2010, 2009, 1995, 1980, 1961, and 1956 that make them good -WPO Dec analogs.

 OTOH, the 2nd list included some that weren’t -ENSO through the winter or at all like 2009, 1989, 1980, and 1956. In addition, 2005 and 1995 had a moderate or strong +PNA in Dec.

 So, what are we left with for the best analogs based on solid -WPO throughout Dec, -ENSO through the winter, and a moderate to strong -PNA in Dec? 2013, 2010, and 1961. Of these three, the PNA flipped to positive in Jan in 2014 and 2011 and to neutral in Jan of 1962.

  So, the closest -ENSO/Dec -WPO/Dec -PNA analogs are 2013, 2010, and 1961.

1 hour ago, BlizzardWx said:

I've been trying to think about what is "going wrong" with such a prolific -WPO to be talking about record warmth down my way. Do you know if a -WPO is typically good for the southern Plains? Is it perhaps atypical to have a -WPO paired with a -PNA or is that typical? I know when I look at the current pattern it seems reasonable to have a west coast trough downstream of that high but maybe sometimes ridging extends further southeast? 

Mostly just trying to build my understanding for this index. 

 I’ll check now for December. These 9 were solidly -WPO Decembers dominating throughout the entire month:

2013, 2010, 2009, 2005, 1995, 1989, 1980, 1961, and 1956. Of these:

1) Cold in the S Plains?

2013, 2009, 2005, 1989, 1961

2) Near normal S Plains?

2010, 1995

3) Mild S Plains?

1980, 1956

 So, strong -WPO Decembers leaned somewhat to the cold side in the S Plains, but only 5 of 9 averaged cold. It looks like this year may end up averaging near normal based on a cold 1st half and mild 2nd half. But we’ll see.

PNA for these 9 Decembers:

2013: moderate -PNA

2010: strong -PNA

2009: weak +PNA

2005: strong +PNA

1995: moderate +PNA

1989: moderate +PNA

1980: weak -PNA

1961: strong -PNA

1956: weak -PNA

 So, PNA for these solidly -WPO Decembers is very mixed.

 Well, as of Dec 13th, the MJO still hasn’t returned to phase 8! It was in 8 only Dec 3rd-7th. Dec 8th-13th have all been in very weak (essentially neutral) phases 5-7. I still think it has a good chance to get back into 8 very soon, but we’ll see:

 The 12/13/25 WPO of -3.48 is the most negative WPO on any day in December since 12/25/1996!

 The only Decembers since 1948 with at least one day lower than -3.48 are:

1996, 1989, 1983, 1977, 1966, 1955

I just took a walk in very refreshing and invigorating 40 degree single digit dewpoint air along with beautiful blue skies and light winds. I love this wx!

OHC has been rising sharply the last 30 days:

21 minutes ago, SnowGoose69 said:

That looks like a lock.  Unfortunately if the PNA is still -2 to -3 that won't work, even getting it to 0 is ideal

Yeah, unfortunately here’s the ugly truth for E US cold preferrers (NG is down another 1% today making it a whopping 26% drop from the peak 11 days ago):

left graph has EPS HDD (latest out/0Z in purple); note the cliff dive it takes from today’s very cold 33 HDD, which is a whopping 10 above the normal of 23, to 12/18’s mild 18, which is 6 below the normal of 24! It later gets as low as 15 on 12/25, which is 10 below the normal of 25!

3 hours ago, Buckethead said:

I'm starting out at 23. I wasn't expecting that!

Sent from my Pixel 10 Pro using Tapatalk
 

2 hours ago, Met1985 said:

Must be something about part of the PV rotating through and out.

 It looks like that’s the case (rotated quickly through and out) per 850 temps on the models:

7PM in degrees C last night near the coldest brrrrr!

1AM last night had already warmed some with coldest already rotating to E NC/VA:

7AM this morning had warmed a lot everywhere!

16 minutes ago, PhiEaglesfan712 said:

Looks like it's completely in the center. That's a bullseye if we're playing darts.

Indeed. The official RMM record always puts it in one of the 8 phases (6, 5, 6, 7, 7 per the bolded below for 12/8-12), but, regardless, this is about as bullseye/weak as you can get for a 5 day period:

2025          12           8  0.16185258      0.31161267               6  0.35113916      Gottschalk10_method:_OLR_&_ACCESS_wind      
        2025          12           9  0.23143651      0.18252292               5  0.29474986      Gottschalk10_method:_OLR_&_ACCESS_wind      
        2025          12          10  0.12193847      0.22910139               6  0.25953120      Gottschalk10_method:_OLR_&_ACCESS_wind      
        2025          12          11 -9.49310213E-02  0.16355878               7  0.18911207      Gottschalk10_method:_OLR_&_ACCESS_wind      
        2025          12          12 -2.23553125E-02  8.96196812E-02           7  9.23658386E-02  Gottschalk10_method:_OLR_&_ACCESS_wind

https://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt

MJO still hadn’t gone back into 8 as of 12/12 with it technically still in a very weak 7 per the record: so, 12/8-12 in very weak phases 5-7 essentially neutral with it not far from the center

38 minutes ago, suzook said:

If you had any cajones, you would go for a walk this morning. Ha, just kidding. Currently 17 degrees here. BRRRRRR.

No, I’ll pass lol.

26.6 is coldest I saw for here (at 7:40 AM)

 The official (airport) low was 25 as of 7AM.

 Cold air (SE style) is always appreciated by cold weenies like me because heat/humidity are so dominant much of the year. I had an invigorating walk just after it went through here early this evening. It was still in the upper to mid 50s, but it still felt so clean and crisp due to the combo of the the wind and dewpoints plunging into the mid-20s! Dry cold gives me so much energy! We’d better enjoy it while we still have it.

 Forecast is for low 20s even down in this area! But there’s still a long ways to go with it still at 43.5 here.

1 hour ago, mitchnick said:

Wish I had seen these before I made this post as I would have stuck them in with it. Stole them from my MA forum. Eps ensemble members for Christmas Day temps. Laughable. 

Thanks, Mitch.

For the MidAtlantic, I roughly estimate 55% AN vs 45% BN. So, quite mixed as you’re implying. Thus, the predictability for Christmas and other days nearby is pretty low.

Despite my more optimistic posts in recent days, I always still try to be objective and show everything, good or bad. The Euro Weeklies remain steadfast on a warmer than average SE and Mid-Atlantic westward/solid -PNA through almost the entire run. The torchiest still remains well to the west of the E/SE US thanks to occasional cool-offs likely largely related to CAD saving the day. The NE is not far from normal.
 It tries to cool off in general in the E US toward normal the last week (1/19-25), but it isn’t really exciting looking.

  I continue to hope that just like the models have performed in many cases for the last 3.5 weeks, that they keep busting too warm in the E US.

11 minutes ago, MJO812 said:

Here comes another period that was supposed to be mild but took a turn to the colder side. 

 This has been going on a lot since the Nov 20th and earlier runs were too warm for Thanksgiving week in much of the E US.