December 2019 Med/Long Range Disco

[Bob Chill]

Figured I'd open a thread for Dec specific discussion now that it's almost in range with ens guidance and it will soon be a hot topic as we roll through the second half of November. 

As I've said multiple times, I don't have high expectations but that doesn't mean I think a lame Dec is a lock. Seasonal/weekly guidance is pretty unanimous with Dec featuring a mean +AO/NAO. And that's certainly possible as it's been a recurring theme for quite awhile now. It's worth discussing the opposite because the Nov mean AO is looking likely to go down as a solid -AO month. If ens guidance is right, the Nov AO should finish at least 1sd BN. There is a decent correlation with Nov AO readings below -1 and December also featuring a -AO.

I dug this spreadsheet out of my archives showing Dec -AO lower than -1.0 and the seasonal snowfall at DCA. Not a bad list but like all lists like this... there are notable outliers and ENSO plays an important role. Overall as a group, having a -AO points towards higher odds of near to above normal snowfall than a disaster. We've discussed this at length so nothing groundbreaking here. 

 

1961 has been showing up at the top of CPC analogs for a while now and it caught my attention so I pulled some composites for Dec 1961. The 61-62 year as a whole kinda sucked in our area for snowfall but that stat is so volatile so you can't just look at that and expect the same result. One notable thing about Dec 61 is it featured a fairly stout -NAO (especially second half) on the means. Total coincidence or possible clue? Not sure but worth taking a look at. 

First half Dec 61:

 

Second half:

 

I'm not thinking Dec 61 overall is a good analog for this year and even with a -NAO the general pattern that year was so-so at best but looking at the NAO in isolation it does pique my interest a little. Ops and ens have been consistently hinting at fairly stable AN heights in the NAO region during the second half of Nov. I don't see all of this as a screaming signal for a -NAO or AO in December yet but looking at all guidance right now it makes me wonder if in fact all these little hints are legit signs that Dec may be a blocky month even though seasonal and weekly guidance says hell no. 

[mappy]

10 year 12/19 anniversary. book it for some snow. 

[psuhoffman]

@Bob Chill 1961-2 was one of the greatest "forum divider" winters in history.  DC had a mediocre winter with only 15" at DCA, but BWI recorded 35" and Winchester and my area had over 50".  That is unusual.  There was a storm on xmas eve that dropped a general 4-8" snowfall to the NW of DC but was mostly rain in the city.  There were a few moderate 3-4" storms in February that were similar and then a big storm early March that was mostly rain in DC but a HUGE snowfall to the NW of the city.  It must have been fairly cold because the local coop up here recorded 40 days of snowcover that year which is high even for up here.  It was also an above normal snowfall winter at most locations north of DC.  Seems DC was just on the SE fringe of where the boundary set up that winter for the handful of significant snowstorms.  But no 2 years are exactly the same...so of course if that were to play out again...and the boundary were 50 miles south we all win.  If its 50 miles north...we all lose.  Or we get a repeat and the DC area tries to kick the northern 1/3 of the region out of the sub-forum.

[psuhoffman]

If we start December like this I am happy 

[WxUSAF]

The consistent Aleutian trough and Scandinavian ridge is nice for sure. Blue ball near the pole less so, but it’s way out there. Verbatim that’s a pattern that could certainly give us snow with a few more weeks of climo cooling temperatures.

[psuhoffman]

2 minutes ago, WxUSAF said:

The consistent Aleutian trough and Scandinavian ridge is nice for sure. Blue ball near the pole less so, but it’s way out there. Verbatim that’s a pattern that could certainly give us snow with a few more weeks of climo cooling temperatures.

For December I would settle for a "workable" pattern given what we typically deal with lately.  

[Bob Chill]

@PSU

It is an interesting look and there's been a slow but noticeable trend with all guidance showing the NAO may start to cooperate. Or at least not be super hostile. The GFS op started spitting out panels like this 3-4 days ago and it caught my eye because it was one after another and not fleeting. This is just a recent run. A bunch of previous op runs kept showing different variations. Now the GEFS are catching on so maybe it's not fantasy. 

Does it really mean anything though? Too soon imo but if there's a continuation and verification as we close out the month then all seasonal/weekly guidance for Dec starts looking very suspect. Which is a good thing in this case. haha

 

@WxUSAF

Yea, no sense worrying about mid latitude patterns yet. Nov is notorious for fooling us with good and bad mid latitude looks. The high latitudes are different and they already look far better than I thought before Nov started. Having favorable high latitudes but crappy mids isn't that bad because it can flip good quickly. Takes a lot more work when high latitudes suck...as we've seen for way too many years in a row now...

[CAPE]

17 minutes ago, psuhoffman said:

If we start December like this I am happy 

EPS is very similar. Looks a bit better out west with a more defined ridge. If this ends up verifying, it will be interesting to see how quickly the NA look breaks down, given what the majority of longer range/seasonal models are depicting for Dec.

[WinterWxLuvr]

Ridge west trough East can also be cold, dry, windy. Might get lucky with a clipper but those don’t seem to exist anymore. We need some flow to under cut that ridge and bring us something to work with. 
 

I’ll never stray from my winter theory of give me precip and I’ll take my chances. It’s not temp that will cause me to not see snow for the next week or so.

[psuhoffman]

1 hour ago, C.A.P.E. said:

EPS is very similar. Looks a bit better out west with a more defined ridge. If this ends up verifying, it will be interesting to see how quickly the NA look breaks down, given what the majority of longer range/seasonal models are depicting for Dec.

The seasonal and monthly guidance has all continued to busy badly even at 1 month leads. The ensembles have been doing better lately our to day 14 or so. After that guidance continues to go off on a tangent. The climo models busted on the current pattern from range. So I really don’t give them any thought and that has nothing to do with the fact I don’t like what they show. I don’t ignite things I dont like. I do ignore things I don’t think have any validity.  

[psuhoffman]

@C.A.P.E. 

PS. The climo models weren’t the basis of my forecast last year either. I only bought them because they matched my analogs and expectations. When I saw in mid January things weren’t going as expected I had my mini melt down. Good or bad the long range seasonal guidance has such awful skill it’s not worth much. 

[BristowWx]

11 minutes ago, WinterWxLuvr said:

Ridge west trough East can also be cold, dry, windy. Might get lucky with a clipper but those don’t seem to exist anymore. We need some flow to under cut that ridge and bring us something to work with. 
 

I’ll never stray from my winter theory of give me precip and I’ll take my chances. It’s not temp that will cause me to not see snow for the next week or so.

I used to think otherwise but now I think we need precip first...cold dry sucks donkey marbles...even under ideal conditions getting snow in the forum is a crap chute...my brother lives just north of DTW and will end up with a third of my seasonal snowfall today in Nov

[WVclimo]

1 hour ago, psuhoffman said:

@Bob Chill 1961-2 was one of the greatest "forum divider" winters in history.  DC had a mediocre winter with only 15" at DCA, but BWI recorded 35" and Winchester and my area had over 50".  That is unusual.  There was a storm on xmas eve that dropped a general 4-8" snowfall to the NW of DC but was mostly rain in the city.  There were a few moderate 3-4" storms in February that were similar and then a big storm early March that was mostly rain in DC but a HUGE snowfall to the NW of the city.  It must have been fairly cold because the local coop up here recorded 40 days of snowcover that year which is high even for up here.  It was also an above normal snowfall winter at most locations north of DC.  Seems DC was just on the SE fringe of where the boundary set up that winter for the handful of significant snowstorms.  But no 2 years are exactly the same...so of course if that were to play out again...and the boundary were 50 miles south we all win.  If its 50 miles north...we all lose.  Or we get a repeat and the DC area tries to kick the northern 1/3 of the region out of the sub-forum.

That early March storm, the Ash Wednesday storm, was one of the most destructive nor'easters in history.  Dropped 18"+ in this area.  Had the stall off of our coast that we always root for, which was incredibly destructive to the towns on the coast.  I'd like to see a storm with that kind of power, but ideally in Jan or Feb.

[CAPE]

37 minutes ago, psuhoffman said:

The seasonal and monthly guidance has all continued to busy badly even at 1 month leads. The ensembles have been doing better lately our to day 14 or so. After that guidance continues to go off on a tangent. The climo models busted on the current pattern from range. So I really don’t give them any thought and that has nothing to do with the fact I don’t like what they show. I don’t ignite things I dont like. I do ignore things I don’t think have any validity.  

They all suck in general. We all know that. Ofc one might ask why anyone would bite on the LR ensembles depiction of a legit -NAO given recent history. I am skeptical until it happens in real time. Looks nice on paper. Lets see what happens. We have seen transient/bootleg stuff, but not a legit block.

[CAPE]

41 minutes ago, BristowWx said:

I used to think otherwise but now I think we need precip first...cold dry sucks donkey marbles...even under ideal conditions getting snow in the forum is a crap chute...my brother lives just north of DTW and will end up with a third of my seasonal snowfall today in Nov

It's not black and white that way. Many times however, having a cold air mass firmly entrenched, with moisture moving into it , gives the best chances for widespread frozen for much of our region. We don't need super cold, just need the correct h5 setup. High pressure over the lakes, Low to the NE off the maritimes.

[psuhoffman]

9 minutes ago, C.A.P.E. said:

They all suck in general. We all know that. Ofc one might ask why anyone would bite on the LR ensembles depiction of a legit -NAO given recent history. I am skeptical until it happens in real time. Looks nice on paper. Lets see what happens. We have seen transient/bootleg stuff, but not a legit block.

A true NAO block is very rare. When it happens we have a high score rate. But the general tendency of ridging in the AO and NAO regions lately I would gladly buy during winter and take my chances. 

[CAPE]

1 minute ago, psuhoffman said:

A true NAO block is very rare. When it happens we have a high score rate. But the general tendency of ridging in the AO and NAO regions lately I would gladly buy during winter and take my chances. 

Yes it is, in winter. Extinct practically. Been what, 9-10 years now?

[frd]

The memorable high impact snowstorms of Jan 1996 and Feb 2003 was moisture moving into an established arctic air mass. 

Careful what you wish for though, as in my general area, the flow eventually rides from far over the Atlantic and warms the upper layers. 

Both the blizzards, 03 and 1996 changed over to sleet in my area while Philly hit something like 33 inches of snow. 

To score in a true sense with snow from start to finish we need ( or certain areas need ) that extreme -NAO which many times will steer that storm ENE versus NE. 

My best storm in the winter of 09-10 was actually the the December storm, which measured 26 inches, OMG, I long for that again!!   

The other two storms in the 09-10 winter did mix. 

The Feb 03 storm though was close to all snow event  here, but eventually I read a 2,000 miles long of Easterly fetches warmed the upper layers, stopping me at about 23 inches, otherwise I would have surely hit well over 30 inches. 

Each high impact snowstorm varies. 

I love snowstorms! 

 

  

 

 

[CAPE]

@psuhoffman

Having an established tendency for HL blocking is fine. That works. I am making a distinction between that and ridging that develops in the NAO space as a result of a deep NS vortex lobe rotating through. That might look impressive on guidance, but it lasts a day or 2 and quickly moves out- that becomes a thread the needle deal for it to work for us.

[CAPE]

4 minutes ago, frd said:

The memorable high impact snowstorms of Jan 1996 and Feb 2003 was moisture moving into an established arctic air mass. 

Careful what you wish for though, as in my general area, the flow eventually rides from far over the Atlantic and warms the upper layers. 

Both the blizzards, 03 and 1996 changed over to sleet in my area while Philly hit something like 33 inches of snow. 

To score in a true sense with snow from start to finish we need ( or certain areas need ) that extreme -NAO which many times will steer that storm ENE versus NE. 

My best storm in the winter of 09-10 was actually the the December storm, which measured 26 inches, OMG, I long for that again!!   

The other two storms in the 09-10 winter did mix. 

The Feb 03 storm though was close to all snow event  here, but eventually I read a 2,000 miles long of Easterly fetches warmed the upper layers, stopping me at about 23 inches, otherwise I would have surely hit well over 30 inches. 

Each high impact snowstorm varies. 

I love snowstorms! 

 

  

 

 

That's just the nature of the beast on the coastal plain. We still get hammered usually in those classic setups.. other than something like 2016 when the poorly modeled dryslot from hell was the culprit. Even so, 'half a storm' produced 15" here.

[frd]

5 minutes ago, C.A.P.E. said:

That's just the nature of the beast on the coastal plain. We still get hammered usually in those classic setups.. other than something like 2016 when the poorly modeled dryslot from hell was the culprit. Even so, 'half a storm' produced 15" here.

 

Exactly just throw me a bone!  

And yeah,  I try not to think about 2016, I believe I measured about 17 inches, while Bob's hood had 5 feet :-) 

[JakkelWx]

6 minutes ago, C.A.P.E. said:

That's just the nature of the beast on the coastal plain. We still get hammered usually in those classic setups.. other than something like 2016 when the poorly modeled dryslot from hell was the culprit. Even so, 'half a storm' produced 15" here.

I hated that dry slot. We stopped at like 13 inches before it sleeted, then a couple inches on the backside. The dry slot caused it to start sleeting because we were too close to the r/s line plus the rates weren't high enough. 

[psuhoffman]

@C.A.P.E. @Bob Chill

Euro ens still looks good to me heading towards December. This look probably won’t get it done in late November but I would take it during peak Climo. And still no signs of the flip up top that the seasonal guidance expects. 

[psuhoffman]

Cross polar flow is great if you want to go ice fishing. But we don’t need it for snow. Air that originated in northern Canada will be cold enough to snow even if it was above normal for them!  

 

[CAPE]

11 minutes ago, psuhoffman said:

@C.A.P.E. @Bob Chill

Euro ens still looks good to me heading towards December. This look probably won’t get it done in late November but I would take it during peak Climo. And still no signs of the flip up top that the seasonal guidance expects. 

Yup I commented on this when you posted the GEFS panel earlier. Let's hope it materializes, and it has some persistence moving  into early winter where climo becomes more favorable. Yeah we all know Dec ends up being just another fall month more times than not, but we are due for a little early winter action. We got jobbed last Dec.

[WinterWxLuvr]

16 minutes ago, psuhoffman said:

@C.A.P.E. @Bob Chill

Euro ens still looks good to me heading towards December. This look probably won’t get it done in late November but I would take it during peak Climo. And still no signs of the flip up top that the seasonal guidance expects. 

I like that look. A broad flat trough with that little bit of baginess in the sw. we can win with that.

[WxUSAF]

@psuhoffman that’s a nice look on the Eps. I like how it’s been fairly insistent on keeping the PNA positive. That’s definitely a look that could produce.

[WinterWxLuvr]

As for the operational, both the Euro and Gfs forecasts for today from just 7 days ago were awful. GFS has my high at about 30. It was 66.

Just need to factor that in when forecasting or hoping for snow more than about 3-5 days in advance.

[Bob Chill]

56 minutes ago, WinterWxLuvr said:

As for the operational, both the Euro and Gfs forecasts for today from just 7 days ago were awful. GFS has my high at about 30. It was 66.

Just need to factor that in when forecasting or hoping for snow more than about 3-5 days in advance.

True but the anomalous cold shot was nailed at long range. Just a timing deviation. The cold front itself has been well modeled by the ops. When they showed a trailing wave snowstorm we all assumed it was fantasy. I get what you're saying pf course. A synoptic even at 7 days on an op has equal chance at any outcome including nothing at all. Lol

[Bob Chill]

1 hour ago, psuhoffman said:

@C.A.P.E. @Bob Chill

Euro ens still looks good to me heading towards December. This look probably won’t get it done in late November but I would take it during peak Climo. And still no signs of the flip up top that the seasonal guidance expects. 

 

I suppose the most important thing to watch now is whether or not seasonal guidance is onto something or just another terrible bust. We certainly don't want what the cfs or euro monthlies are showing. Barf

I am curious as to how the weeklies roll the current d15 forward. Dec is only 3 weeks away now...