December 2019 Med/Long Range Disco

[psuhoffman]

@Bob Chill how would you like to try the high lattitude look of 1997/98 without the mid latitude pac firehose flood from the super nino?  Just a thought.  On a more serious note its nice to be heading towards the holidays with guidance trending towards a cold/stormy look.  

[yoda]

7 minutes ago, psuhoffman said:

QBO for November cam in at 5.07.  Looking at the progression the closest matches to this year are 

2004, 2002, 1997, 1978, and 1969.  Of those the best match purely on QBO continues to be 2002 with the last 3 months all being nearly identical.  Of the 15 winter months those years the AO was negative 12/15 months.  The only year of those that didn't feature a -AO for 2/3 months was 2004-5 but it is notable that year started with an extremely +AO and flipped mid January.  

There were 2 other years that were somewhat close, 1955 and 1961.  If we include those the AO was negative 17/21 months.  

2002-2003 had 40.4" of snowfall -- but that was punctuated with the big Feb 2003 snowstorm

1955-1956 was a crappy winter at DCA... 11.3" of snowfall

1961-1962 was an average winter... snow was spread out over Dec-March for a total of 15.0" (Nov 1961 had 1.3" of snow)

Snowfall records found here -- https://www.weather.gov/media/lwx/climate/dcasnow.pdf

[anotherman]

1 minute ago, psuhoffman said:

@Bob Chill how would you like to try the high lattitude look of 1997/98 without the mid latitude pac firehose flood from the super nino?  Just a thought.  On a more serious note its nice to be heading towards the holidays with guidance trending towards a cold/stormy look.  

I think we all fear a tropical Christmas.  It's the ultimate weenie nightmare.

[WxUSAF]

@frd what of those dates were good? None jump to mind.

[Bob Chill]

3 minutes ago, psuhoffman said:

@Bob Chill how would you like to try the high lattitude look of 1997/98 without the mid latitude pac firehose flood from the super nino?  Just a thought.  On a more serious note its nice to be heading towards the holidays with guidance trending towards a cold/stormy look.  

I'd be good with that. Honestly, I'd be good with a repeat of any year that was decent in the high latitudes but ended up crappy because mid latitude stuff screwed it up. Conversely.... I wouldn't want to take my chances again with a 2013/14 pattern. That year was famously amazing but the way things happened defied a more typical outcome. Next time we get an -EPO/++AO/++NAO pattern I can almost guaranty nobody will be happy with the outcome. lol

[Inthepines]

6 minutes ago, WxUSAF said:

@frd what of those dates were good? None jump to mind.

12/82 was the "snowjam" event I believe. Dec. 1960 was a good month also.

[Bob Chill]

6 minutes ago, anotherman said:

I think we all fear a tropical Christmas.  It's the ultimate weenie nightmare.

If the 12z gfs -EPO on HGH and steroids happens then we don't have to worry at all. A giant closed off upper level ridge in this area will continuously dump cold into the CONUS. Probably for weeks. lol

 

 

Of course this is fantasyland stuff but the -EPO ridge builds within 5 days and just goes bonkers from there. Keeps looking blockier in the long range too. Like many here, I'm feeling good about the second half of Dec

 

[poolz1]

12z GFS with an EPO ridge on roids the entire run.  

 

ETA: Bob with a better description..and graphics! lol

[Bob Chill]

I'm digging how guidance is shifting towards a more broad conus trough down the line instead of a vertical ridge/trough setup. The broader the trough axis the more chances we get for a widespread event instead of praying for a perfectly timed shortwave to round the base and praying even harder that the 100 mile wide swath of precip makes it over our yards. Lets have a big drawn out overrunning event that plasters the TN valley and MA. 

[osfan24]

It's an OP at range so who cares I guess, but I sure would have loved to have seen what was about to happen on the GFS at the end of the 12z run.

[psuhoffman]

9 minutes ago, Bob Chill said:

If the 12z gfs -EPO on HGH and steroids happens then we don't have to worry at all. A giant closed off upper level ridge in this area will continuously dump cold into the CONUS. Probably for weeks. lol

 

 

Of course this is fantasyland stuff but the -EPO ridge builds within 5 days and just goes bonkers from there. Keeps looking blockier in the long range too. Like many here, I'm feeling good about the second half of Dec

 

I was just joking in banter (because it’s 2 weeks away) but the gfs really is setting up a big pre Xmas snowstorm at the end. 

[Bob Chill]

1 minute ago, psuhoffman said:

I was just joking in banter (because it’s 2 weeks away) but the gfs really is setting up a big pre Xmas snowstorm at the end. 

GEFS looks as good as you can ask without a -NAO... Split flow, broad trough, nasty EPO ridge dumping arctic air, -AO building to keep the TPV from running away.... 

[frd]

14 minutes ago, WxUSAF said:

@frd what of those dates were good? None jump to mind.

Reading from a met who stated some of those looks within  a greater window of 30 days,  not the date centered on 12/14 , so going towards and including 12/28 have produced some significant EC snow events, including significant over running snowfall producers going from the Tennessee Valley to the Northern Mid Atlantic.  I am thinking he did a roll over from that CPC depiction, but not sure.  

[frd]

31 minutes ago, psuhoffman said:

QBO for November came in at 5.07.  Looking at the progression the closest matches to this year are 

2004, 2002, 1997, 1978, and 1969.  Of those the best match purely on QBO continues to be 2002 with the last 3 months all being nearly identical.  Of the 15 winter months those years the AO was negative 12/15 months.  The only year of those that didn't feature a -AO for 2/3 months was 2004-5 but it is notable that year started with an extremely +AO and flipped mid January.  

There were 2 other years that were somewhat close, 1955 and 1961.  If we include those the AO was negative 17/21 months.  

I feel this is great news. Regardless of the closet match, keep it going down.  Hopefully this is another positive added to the mix for Jan through March. 

Some folks were concerned it might stall. 

[Scarlet Pimpernel]

13 minutes ago, Bob Chill said:

I'm digging how guidance is shifting towards a more broad conus trough down the line instead of a vertical ridge/trough setup. The broader the trough axis the more chances we get for a widespread event instead of praying for a perfectly timed shortwave to round the base and praying even harder that the 100 mile wide swath of precip makes it over our yards. Lets have a big drawn out overrunning event that plasters the TN valley and MA. 

Funny, but as I was reading the first part of your post quoted here, after looking at the GFS (and GEFS) 500-mb plot...my first thought was "ohhh, overrunning would be nice with that look!"  Two minds and all that, right?  Anyhow, yeah, such an event would be great, as long as we avoid a hugely amplified wave I suppose (not much blocking).  I know we're talking fantasy land time range at this point, but still.

[UniversesBelowNormal]

Remember last Summer-October it looked like it was going to keep pouring snow/cold chances through the Winter.. It moderated in October-November to 60s/cloudy. You have to wonder.. 

[Bob Chill]

GEFS is showing a decent threat window from the 15th-17th. The mean jumps from practically nothing to this in just a few days... QPF/MSLP panels also show a coastal track. 

 

This is the first time I've seen the GEFS latch onto a specific event. We have 12 days to over analyze and freak out. 

[psuhoffman]

32 minutes ago, yoda said:

2002-2003 had 40.4" of snowfall -- but that was punctuated with the big Feb 2003 snowstorm

1955-1956 was a crappy winter at DCA... 11.3" of snowfall

1961-1962 was an average winter... snow was spread out over Dec-March for a total of 15.0" (Nov 1961 had 1.3" of snow)

Snowfall records found here -- https://www.weather.gov/media/lwx/climate/dcasnow.pdf

The QBO alone doesn’t have much correlation to snowfall. That’s because there are a number of other factors that determine that.  But the QBO does have a correlation to the high lattitide patterns.  There are other things that can wreck even a good high latitude look though. 1956 was a moderate Nina. 97/98 was a raging super nino. 2004/5 had to overcome the worst start imaginable that left North America void of cold early in the season which probably delayed and muted the results later. 2002/3 was likely a positive outlier due to the moderate nino. The details matter. But we can use the qbo to glean some hints at what the base state of the AO might be this year. The rest of the details of the pattern need to be examined independently of that.   One interesting note, several of those years did feature snow in our area around Xmas. 

[psuhoffman]

52 minutes ago, Bob Chill said:

I'd be good with that. Honestly, I'd be good with a repeat of any year that was decent in the high latitudes but ended up crappy because mid latitude stuff screwed it up. Conversely.... I wouldn't want to take my chances again with a 2013/14 pattern. That year was famously amazing but the way things happened defied a more typical outcome. Next time we get an -EPO/++AO/++NAO pattern I can almost guaranty nobody will be happy with the outcome. lol

I think 2013/14 the high latitudes got a bum rap.  The numbers were skewed by a couple of extreme AO spikes in December and February, but actually much of that winter the AO was pretty cooperative.  January came in with a -AO and December and Feb had -AO periods but came in positive due to extremely +weeks.  But I would roll with this h5 look for the winter again and again and again. 

 

If you meant 2014/15 then I agree 100%.  That year was a total fluke given the raging +AO/NAO and likely wouldn't work out if we tried to repeat it again.  

An EPO driven pattern alone is unlikely to work.  That is why the EPO has very low correlation to snowfall.  West based EPO ridges are useless.  An EPO ridge if the PNA/NAO/AO are all wrong won't help too much usually.  But certain specific types of EPO driven patterns when an EPO ridge is working in tandem with the AO or PNA or with a displaced TPV in eastern Canada can be very favorable for snow.  It's not a HECS look, more a progressive waves type setup.  That said if we get a 4-8" snowstorm from a boundary wave the week before xmas and someone complains they need to be given a timeout!  ATT the look the GEFS is throwing out there is one that can work.  Like you said, the broad trough look is a lot better.   Of course that look will shift some and the details will be really important to our snowfall chances.  

[psuhoffman]

Op euro going towards the broad trough idea too. And this look is intriguing. This is a case where some SE ridge is ok. Good luck getting a cutter with that blocking over a severely displaced TPV. 

the boundary hanging out just to our south. 

If we can get these looks into the medium range things could get fun in here. 

[Bob Chill]

Euro/GFS look nearly the same with the EPO ridge closing off and creating a block.  This is getting very interesting. Big storm potential at the end of the euro as well. Prob too fast but late next week in becoming increasingly intriguing. 

[Bob Chill]

CAD/block will win the battle here. 

 

[Wonderdog]

1 minute ago, Bob Chill said:

CAD/block will win the battle here. 

Uh oh, Friday the 13th.

[LP08]

Damn you guys are fast.  Was just saving those images, lol.  That's a big storm look at day 10.  GFS had the low run up west then jump to the coast once north of us.

[Superstorm]

CAD/block will win the battle here. 
 

TEXT BOOK!!


.

[psuhoffman]

Euro setting up a storm day 10. Would probably be snow to ice given the setup. Also looks to be reloading the pattern after with the same ape epo ridge the gfs has. Better AO though. I’ll be happy if the EPS supports the op. 

 

[Bob Chill]

Just now, LP08 said:

Damn you guys are fast.  Was just saving those images, lol.  That's a big storm look at day 10.  GFS had the low run up west then jump to the coast once north of us.

Just a hunch but my guess is the euro type scenario is too quick. It sure looks like the best chance of the season is setting up near mid month though. 

[Wonderdog]

 

 

 

 

 

 

End of the run on the GFS looks promising as well!

[LP08]

3 minutes ago, Bob Chill said:

Just a hunch but my guess is the euro type scenario is too quick. It sure looks like the best chance of the season is setting up near mid month though. 

Definitely.  The ensembles have been hinting at this period for a while now, I remember making a post about it.  We usually don't score at the beginning of the pattern though.

 

One thing I have noticed this year compared to last year and this is completely anecdotal, but with regards to 10 days, the Ensembles and OP of the GFS and EURO are pretty similar at H5.  I remember last year that we had all those good looks out in time but the OP runs never really showed anything similar.   

[Bob Chill]

9 minutes ago, psuhoffman said:

Euro setting up a storm day 10. Would probably be snow to ice given the setup. Also looks to be reloading the pattern after with the same ape epo ridge the gfs has. Better AO though. I’ll be happy if the EPS supports the op. 

 

All in good fun being so far out but this would be an all frozen storm for most. Especially west of 95. No way this depth of CAD gets dislodged. 

 

ETA:

Surface wind out of the N/NE all the way down to GA. Notice the little spin near Savannah GA? There's the jump. lol.