December 2017 Mid-Long Range Disco 2

[WxUSAF]

On a roll so far, but looks like our luck may soon (hopefully briefly) run out.  

[Bob Chill]

I was going to expand on my previous post by wxusaf locked me out! lol

SE ridge and a +NAO is a fairly common winter pattern. Not all SE ridges are created equal because sometimes all of NA is warm anyways and even when fronts from through it's nothing but replacing warm air from the SE with modified pac maritime air. That type of setup is a complete disaster. The upcoming pattern does have a silver lining. The cold loading pattern in Canada is strong. There is going to be a lot of cold continental air dumping into the western 2/3rds of the conus. Full agreement there. Also, Se ridges are not static meaning fronts can penetrate (especially at our latitude) but progressive flow will keep the cool periods short and warm periods long on either side of fronts. 

IMHO- the biggest threat for winter wx coming up is cad/ice or pellets. Sure, if we can get a cold hp to press then snow enters the picture but you'll be hard pressed to find many snow analogs with the upcoming d9+ progs. Thankfully, ens guidance does progress the mean trough over the conus eastward over time but it's going to be a nerve wrenching process. I still feel pretty optimistic that the crappy stuff were looking at right now will be over before the month is done. Doesn't look very likely that it happens before Christmas though. Fasten your seatbelts. lol

[showmethesnow]

Actually just looked at the 00Z GEPS. For what it's worth it shows the SW trough to be much weaker then the EPS and GEFS as well as transitory in nature. SER is also much weaker as well and would possibly put us in play over the holidays as far as where the boundary would set up. We can only hope.

[WxUSAF]

1 minute ago, Bob Chill said:

I was going to expand on my previous post by wxusaf locked me out! lol

 

That guy is #TheWorst

 

[WxUSAF]

2 minutes ago, Bob Chill said:

I was going to expand on my previous post by wxusaf locked me out! lol

SE ridge and a +NAO is a fairly common winter pattern. Not all SE ridges are created equal because sometimes all of NA is warm anyways and even when fronts from through it's nothing but replacing warm air from the SE with modified pac maritime air. That type of setup is a complete disaster. The upcoming pattern does have a silver lining. The cold loading pattern in Canada is strong. There is going to be a lot of cold continental air dumping into the western 2/3rds of the conus. Full agreement there. Also, Se ridges are not static meaning fronts can penetrate (especially at our latitude) but progressive flow will keep the cool periods short and warm periods long on either side of fronts. 

IMHO- the biggest threat for winter wx coming up is cad/ice or pellets. Sure, if we can get a cold hp to press then snow enters the picture but you'll be hard pressed to find many snow analogs with the upcoming d9+ progs. Thankfully, ens guidance does progress the mean trough over the conus eastward over time but it's going to be a nerve wrenching process. I still feel pretty optimistic that the crappy stuff were looking at right now will be over before the month is done. Doesn't look very likely that it happens before Christmas though. Fasten your seatbelts. lol

I just looked at the EPS meteograms on wx.graphics and even with that absolutely craptacular 500mb look, the few days around Xmas were actually slightly colder on the 0z run than the 12z yesterday and the predicted snow jumped also (and the high end jumped a bunch).  

[Cobalt]

If you take the GEFS and look at individual members, it looks like either we get shutout or we get slammed in terms of wintry weather. Basically none of them are in between.

[BristowWx]

1 minute ago, Cobalt said:

If you take the GEFS and look at individual members, it looks like either we get shutout or we get slammed in terms of wintry weather. Basically none of them are in between.

More shut out than slammed I would imagine.  

[Bob Chill]

8 minutes ago, WxUSAF said:

I just looked at the EPS meteograms on wx.graphics and even with that absolutely craptacular 500mb look, the few days around Xmas were actually slightly colder on the 0z run than the 12z yesterday and the predicted snow jumped also (and the high end jumped a bunch).  

All ens are doing that in the long range. I assume it's byproduct of strong + anoms east of the boundary and vice versa. It's pretty complicated figuring our sensible wx right now because of the all or none nature of the setup. The tell will be if the ens start pegging a date for the neg temp anomalies to settle in. 

Just spitballing but I'm starting to envision a step down process where cold comes in little blasts as the mean axis slowly shifts east before a final (probably cutter) pushes the boundary for good.

[BristowWx]

11 minutes ago, Bob Chill said:

All ens are doing that in the long range. I assume it's byproduct of strong + anoms east of the boundary and vice versa. It's pretty complicated figuring our sensible wx right now because of the all or none nature of the setup. The tell will be if the ens start pegging a date for the neg temp anomalies to settle in. 

Just spitballing but I'm starting to envision a step down process where cold comes in little blasts as the mean axis slowly shifts east before a final (probably cutter) pushes the boundary for good.

These things tend to take way longer than expected.  That step down could take the rest of the month and then we lose another key ingredient like the EPO.  

[yoda]

Looking back at the super happy hour 18z GFS of yesterday, this was probably discussed, but the reason we were flying on a magical carpet ride of enjoyment on that run was most likely because the PV came to visit the northern parts of the US (MN/WI/MI).  This, in turn, pressed the cold air south and got the 540 line way south of us. 

[Ralph Wiggum]

If you take the GEFS and look at individual members, it looks like either we get shutout or we get slammed in terms of wintry weather. Basically none of them are in between.

My gut says shutout (maybe years of experience setting expectations low?) but something else keeps saying "Hey, snap out of it.....this year is different so far. We have been trending the right way with early systems and things have been working in our favor". Something is telling me even if this moderation period happens we are going to break out in a big way when it breaks.

[Bob Chill]

5 minutes ago, Ralph Wiggum said:

34 minutes ago, Cobalt said:

If you take the GEFS and look at individual members, it looks like either we get shutout or we get slammed in terms of wintry weather. Basically none of them are in between.
 

My gut says shutout (maybe years of experience setting expectations low?) but something else keeps saying "Hey, snap out of it.....this year is different so far. We have been trending the right way with early systems and things have been working in our favor". Something is telling me even if this moderation period happens we are going to break out in a big way when it breaks.

Shutout is probably too strong of a word right but I agree with you. Many of us have been doing this routine for 10+ years here. We've seen the SER/+NAO many times before. It happens. I posted about this earlier but it does seem to be a typical "snap back" with the re-arrangement of the conus ridge/trough. We've had an eastern trough dominating in general since right around Thanksgiving. The intermountain west/southwest has been very warm and dry so far this cold season. This kind of stuff always evens out or at least catches up some. 

[showmethesnow]

Good sign we are seeing the closed low/trough getting ejected quicker out of the SW in the earlier part of the run?

[yoda]

3 minutes ago, showmethesnow said:

Good sign we are seeing the closed low/trough getting ejected quicker out of the SW in the earlier part of the run?

I think so.  I am also watching the placement of the 540 line

[showmethesnow]

2 minutes ago, yoda said:

I think so.  I am also watching the placement of the 540 line

Still think early next week is worth keeping an eye on though odds are probably long considering it would most likely be cold chasing warm.

[Bob Chill]

14 minutes ago, showmethesnow said:

Good sign we are seeing the closed low/trough getting ejected quicker out of the SW in the earlier part of the run?

Probably can't take away much from the op run in that regard. The progression is multiple troughs digging in the SW. They will eject but if they keep occurring it will keep pumping heights in the SE. We need a pattern shaker to come out of the southwest and establish a more permanent trough in the east. That's going to be a process. My guess anyways but I'll take any op run that ejects it all out of the SW and keeps it that way. lol

[WhiteoutWX]

Biggest difference I'm seeing so far through 180 is lower heights over the Northeast and eastern Canada (from better Greenland ridging) which is in turn dampening out the SE ridging from 0 and 6z GFS runs. 

[yoda]

Beginning to see frozen precip break out in S TX at 210... I think this might be the wave we are looking for.  Also note that a part of the PV seems to be dropping in as well just NE of MN... 486 DM

large area of 492 DM in SE Canada at 222... as well as a 1036 H in MN/IA

[mitchnick]

30 minutes ago, Bob Chill said:

Shutout is probably too strong of a word right but I agree with you. Many of us have been doing this routine for 10+ 40+ years here. We've seen the SER/+NAO many times before. It happens. I posted about this earlier but it does seem to be a typical "snap back" with the re-arrangement of the conus ridge/trough. We've had an eastern trough dominating in general since right around Thanksgiving. The intermountain west/southwest has been very warm and dry so far this cold season. This kind of stuff always evens out or at least catches up some. 

FIXED

[WhiteoutWX]

Yet another totally new solution...SW trough cuts off allowing northern stream wave to head east. It's a tightrope solution though. No way models are going to handle this many complex interactions with any accuracy at this range. 

[Ralph Wiggum]

Much better look.....closed low over SW with pieces of energy ejecting as opposed to one mean longwave trof pumping heights in the East. Allows Northeast to be under influence of 500mb trof keeping it colder and better frozen chances.

[showmethesnow]

This is the way to get it done with a SW trough. Pv shoved southward by the Greenland ridging. But can we count on seeing a -NAO? Hasn't been verifying too well yet this winter.

[mitchnick]

3 minutes ago, yoda said:

Beginning to see frozen precip break out in S TX at 210... I think this might be the wave we are looking for

Boundary thru 228 hours is further south than last run, but next run could be the opposite. The models have know certain clue about this at this point.

[Amped]

Just now, WhiteoutWX said:

Yet another totally new solution...SW trough cuts off allowing northern stream wave to head east. It's a tightrope solution though. No way models are going to handle this many complex interactions with any accuracy at this range. 

Yeah looks way better this run. Also some ridging over Greenland.

[yoda]

I like the look of hr 240 on 12z GFS... 1040 H is moving in tandem

[mitchnick]

2 minutes ago, Amped said:

Yeah looks way better this run. Also some ridging over Greenland.

trough in the SW getting stronger....that won't help down the line on this run

[showmethesnow]

Stay on the north side of the boundary with that cutoff in Baja and I can see some serious juice coming up from the tropics over riding the cold.

[mitchnick]

the other issue is, will the system get squished while the trough is to our north and then come up the back side warm once the trough to the NE pulls out

[yoda]

Nice CAD at 264... Day 11 ice ftw

[SomeguyfromTakomaPark]

Looks like a CAD setup on Christmas with the 1037 high over NY.  Interesting.