December 18-20 Potential Talking Points

[earthlight]

Let's try and drive the discussion home on this storm system in this thread.

I think there's something to be said for the proposed developing west to east (or elongated) polar vortex over southeast Canada. Some of our more memorable setups have come with that type setup in the height field in that area. That being said, some of our most major winter disappointments have arisen from that type of setup as well. We actually are receiving a bunch of wonderful developments as far as the evolution of a winter weather pattern on this side of the country goes--and they are starting right now with the weather you are experiencing outdoors. The big cold front and upper level phase occurring will bring in arctic air and arctic heights, which will meander for a few days before shifting slightly north.

At that point in time, the critical development occurs, which is the extremely anomalous height field which builds into Greenland and Canada--and then retrogrades westward with time. It has been a very long time since I have seen this type of development; where the ECMWF weeklies had indicated the first glimpse of this potential development, which then transcended into the GEFS means and is now becoming a reality. This blocking actually develops in such a fashion from the Western Atlantic that it elongates itself and retrogrades, see the first +96hr panel here, and then becomes established over a position that is exceedingly far west and more favorable than anything we have seen this season (see the +156hr panel here).

This type of blocking harbors an extremely volatile confluent flow over Southeast Canada, which has virtually nowhere to go. If one were to loop the H5 developments aloft, even on the suppressed GFS, you could see this clearly. What then becomes somewhat of a crapshoot, if you will, is the amplification of this vortex as it potentially drops in/phases into a Pacific shortwave. I've heard several skeptics say, and rightly so given how difficult it is to get a snowstorm on the coastal plain, that this is a thread the needle type event. The truth is, every event is a thread the needle event on the east coast, but this one is much less so than most when you actually look at the potential objectively. This is to say that if one shortwave doesn't get the job done, the potential is definitely there for another to phase and amplify. See the 12z ECMWF, which brings us one big snowstorm, and then brings us 50 miles from another just a day or two later as another shortwave shoots across the CONUS, and the elongated polar vortex drops in once again.

I think there should be a general sense of excitement with this pattern. We are still certainly a ways off, with tons of time, but the developments we are seeing on most guidance the past few days harbor the potential for a significant snowstorm all the way to the coast--moreso than any height pattern we have seen yet this winter, and probably since the beginning of February of last winter season.

[blizzardof09]

Enjoyed Reading your post earthlight with the potential in next weekends possible storm and the pattern that could produce a snowstorm for the east coast. Still like 7 days out and a lot of details to iron out and as I've learned the past few winters model waffling too haha. Still learning but am excited that this is the real first legitimant threat this winter for the east coast to track and get excited for

[Ridingtime]

Earthlight, thanks for the awesome discussion. You explain things amazingly clear and it's a delight to learn from your posts. Keep it up!

[Rib]

Appreciate the discussion, yeah, I'm trying to not get into any specifics until we are much further in.

[SomeguyfromTakomaPark]

Nice discussion,

Thanks for breaking down the pattern in an easy to understand way.

[CooL]

you have without doubt the most clear, concise, and juicy discussions on this board ...i have been trying to get this answer, but what is the gfs doing with the storm? is the s/w not amp'd enough? not enough ridging? i'd like to get the gfs on board asap

[earthlight]

Thanks to all for the comments and discussion. The GFS is too far south because it's struggling with the strength and positioning of the Polar Vortex over the Northeast US, and is also jumping around with the positioning of the shortwave over the Central United States. It's pretty much a testament to the continued uncertainty in the pattern. Despite the fact that we have a ton of things in place that give this pattern more positives than negatives, there will always be a ton of uncertainties and things that can go wrong. And the PV and block being too far south is one of them. That being said, I think the potential comes to fruition eventually with this blocking--even if it's not on these specific dates in the thread title.

[daxx]

Great info!!!

[Ridingtime]

Thanks to all for the comments and discussion. The GFS is too far south because it's struggling with the strength and positioning of the Polar Vortex over the Northeast US, and is also jumping around with the positioning of the shortwave over the Central United States. It's pretty much a testament to the continued uncertainty in the pattern. Despite the fact that we have a ton of things in place that give this pattern more positives than negatives, there will always be a ton of uncertainties and things that can go wrong. And the PV and block being too far south is one of them. That being said, I think the potential comes to fruition eventually with this blocking--even if it's not on these specific dates in the thread title.

DT also said the GFS has a hard time recognizing the STJ and moisture that comes from that, which makes it yield it's poor results in the long range. But that could have just been DT barking his hate of the GFS model.

[easternsnowman]

GOOD discussion here one forum has ji and the usual downer crowd.

[ptb127]

Great discussion Earthlight.. There is a sense of excitement but the problem is, is that if you're in an area that doesn't get hit hard or hit at all there will be a sense of disappointment. I say this because there is a possibility that areas that aren't suppose to see big snowstorms see one and the areas that are more climo favored miss out on the heaviest stuff. I am hoping that we when close the chapter on this storm, that all of us in this area are happy

[A-L-E-X]

Thanks to all for the comments and discussion. The GFS is too far south because it's struggling with the strength and positioning of the Polar Vortex over the Northeast US, and is also jumping around with the positioning of the shortwave over the Central United States. It's pretty much a testament to the continued uncertainty in the pattern. Despite the fact that we have a ton of things in place that give this pattern more positives than negatives, there will always be a ton of uncertainties and things that can go wrong. And the PV and block being too far south is one of them. That being said, I think the potential comes to fruition eventually with this blocking--even if it's not on these specific dates in the thread title.

Thanks for the illuminating discussion, John, and yea, this is a cliche but I think we can safely say the GFS is where we want it to be right now.  It's sure as hell a lot better than if the GFS and Euro flip flopped from this far out.

[CooL]

GFS is out to sea but it looks really whack. Hour 216 is for giggles. This could be the gfs supression bias at play, things look very zonal before the storm gets ots..

[Kaner587]

GFS is out to sea but it looks really whack. Hour 216 is for giggles. This could be the gfs supression bias at play, things look very zonal before the storm gets ots..

Unless I'm reading something wrong, the GFS has the STJ s/w but it doesnt phase with the PJ because the timing isnt right, therefore its just a southern stream disturbance that slides out to sea. How many times have we seen that on the GFS in the medium range?

[jrodd321]

GFS is out to sea but it looks really whack. Hour 216 is for giggles. This could be the gfs supression bias at play, things look very zonal before the storm gets ots..

GFS now shows a storm sliding off the coast around 174-180 that it didn't have at 12z. Maybe finally starting to catch on.

[Edge Weather]

Yes, very much a typical GFS bias. The GFS does much better with Northern stream systems than southern stream ones. It is likely messing up the southern stream energy completely and putting too much emphasis on the northern stream.

Unless I'm reading something wrong, the GFS has the STJ s/w but it doesnt phase with the PJ because the timing isnt right, therefore its just a southern stream disturbance that slides out to sea. How many times have we seen that on the GFS in the medium range?

[Kaner587]

it seems like some people only look at the surface features when its the upper level features that will tell you where this is going

[NortheastPAWx]

Good discussion...looks like some late nights coming up for all of us (for me, after tonight).

[earthlight]

Great discussion Earthlight.. There is a sense of excitement but the problem is, is that if you're in an area that doesn't get hit hard or hit at all there will be a sense of disappointment. I say this because there is a possibility that areas that aren't suppose to see big snowstorms see one and the areas that are more climo favored miss out on the heaviest stuff. I am hoping that we when close the chapter on this storm, that all of us in this area are happy

Good points, but I am of the belief that this is the case in almost every snowstorm except for the all-time greats. There will always be an area that gets fringed, or an area that gets screwed. There can be a highly anomalous and favorable pattern like this one, but there will always be a loser. This one just happens to favor the area in this subforum.

[earthlight]

DT also said the GFS has a hard time recognizing the STJ and moisture that comes from that, which makes it yield it's poor results in the long range. But that could have just been DT barking his hate of the GFS model.

This is certainly a possibility. What's interesting is how different it is from the ECMWF aloft. The GFS shortwave comes straight from the Northern Pac Jet, from Montana. At the same time frame the ECMWF has the shortwave of interest (the one that phases in with the Polar Vortex over southeast Canada) over the Southwest states and then ejecting northeast.

[NortheastPAWx]

Good points, but I am of the belief that this is the case in almost every snowstorm except for the all-time greats. There will always be an area that gets fringed, or an area that gets screwed. There can be a highly anomalous and favorable pattern like this one, but there will always be a loser. This one just happens to favor the area in this subforum.

I think people like me and ptb certainly have our reasons for worry...we were both screwed on some of the recent big ones.

[Ace]

http://raleighwx.americanwx.com/models/gfsensemble/18zgfsensemble500mbHGHTtropical180.gif

Pretty strong signal this far out. 994mb

[earthlight]

http://raleighwx.americanwx.com/models/gfsensemble/18zgfsensemble500mbHGHTtropical180.gif

Pretty strong signal this far out. 994mb

Yeah--the GFS Ensembles have been signaling this for a few guidance suites now, as have the ECMWF and GGEM means. The individual members at 12z had 2 or 3 members which showed snowstorms along the coast--that's more than adequate for me at this range. Having a 994mb surface low east of the benchmark on the means at this range is certainly nothing to complain about. What's more interesting is the signal for amplification..those are 522 dm closed heights over the Northeast at 162-168 hours.

[SmokeEater]

I think people like me and ptb certainly have our reasons for worry...we were both screwed on some of the recent big ones.

Nobody should worry at this point, it's too far out. Anybody could get shafted, so to say some should worry more than others, way too early for that.

[earthlight]

The super ensemble analog plots are very impressive this evening--with some pretty cool dates on the top analogs list. Also-the blocking being depicting is definitely nearing historic levels now on most ensemble means.

[earthlight]

The 12z/+96hr ECMWF seems to have some significant support from the 00z/+84 hr NAM in regards to it's upper level height field and shortwave orientation. Not really worth all that much, but it's something to chew on while we wait for the remainder of this 00z suite.

http://www.meteo.psu.edu/~gadomski/WRF_0z/f84.gif

http://www.meteo.psu.edu/~gadomski/ECMWF_12z/f96.gif

[jwilson]

I suppose it makes sense that the only chance the East has for snow in a strong La Nina winter is historic blocking and a venerable -AO push. Are those factors going to be enough to overcome weaknesses elsewhere? Are there any analogs that may help predict an outcome? We realize that typically a Mid-Atlantic snowstorm requires almost everything to fall in-line. That tempers my optimism in the mean time.

[Kaner587]

I suppose it makes sense that the only chance the East has for snow in a strong La Nina winter is historic blocking and a venerable -AO push. Are those factors going to be enough to overcome weaknesses elsewhere? Are there any analogs that may help predict an outcome? We realize that typically a Mid-Atlantic snowstorm requires almost everything to fall in-line. That tempers my optimism in the mean time.

Only chance at BIG snow...It snows in La Nina winters, we just seem to lack the big event. Blocking like this (-nao) in conjunction with the tanking -AO puts us in unchartered territory so your guess is as good as mine. For the record my guess is one of these s/w phases and we get a KU but not necessarily this upcoming one.

[bmc10]

Let's try and drive the discussion home on this storm system in this thread.

I think there's something to be said for the proposed developing west to east (or elongated) polar vortex over southeast Canada. Some of our more memorable setups have come with that type setup in the height field in that area. That being said, some of our most major winter disappointments have arisen from that type of setup as well. We actually are receiving a bunch of wonderful developments as far as the evolution of a winter weather pattern on this side of the country goes--and they are starting right now with the weather you are experiencing outdoors. The big cold front and upper level phase occurring will bring in arctic air and arctic heights, which will meander for a few days before shifting slightly north.

At that point in time, the critical development occurs, which is the extremely anomalous height field which builds into Greenland and Canada--and then retrogrades westward with time. It has been a very long time since I have seen this type of development; where the ECMWF weeklies had indicated the first glimpse of this potential development, which then transcended into the GEFS means and is now becoming a reality. This blocking actually develops in such a fashion from the Western Atlantic that it elongates itself and retrogrades, see the first +96hr panel here, and then becomes established over a position that is exceedingly far west and more favorable than anything we have seen this season (see the +156hr panel here).

This type of blocking harbors an extremely volatile confluent flow over Southeast Canada, which has virtually nowhere to go. If one were to loop the H5 developments aloft, even on the suppressed GFS, you could see this clearly. What then becomes somewhat of a crapshoot, if you will, is the amplification of this vortex as it potentially drops in/phases into a Pacific shortwave. I've heard several skeptics say, and rightly so given how difficult it is to get a snowstorm on the coastal plain, that this is a thread the needle type event. The truth is, every event is a thread the needle event on the east coast, but this one is much less so than most when you actually look at the potential objectively. This is to say that if one shortwave doesn't get the job done, the potential is definitely there for another to phase and amplify. See the 12z ECMWF, which brings us one big snowstorm, and then brings us 50 miles from another just a day or two later as another shortwave shoots across the CONUS, and the elongated polar vortex drops in once again.

I think there should be a general sense of excitement with this pattern. We are still certainly a ways off, with tons of time, but the developments we are seeing on most guidance the past few days harbor the potential for a significant snowstorm all the way to the coast--moreso than any height pattern we have seen yet this winter, and probably since the beginning of February of last winter season.

John, pretty much in agreement. Definitely some potential with this pattern. I am encouraged because unlike what is occurring right now, we will actually have confluence/blocking in place to prohibit anything from amplifying and cutting. If the polar vortex can hook up with the wave entering from the Pacific, we are in business. Encouraging is the slight ridging out west, which would help slow the pattern and allow the shortwave to amplify, allowing the trough to go negative. The pattern has been so progressive that when it has been cold we just can't get anything to develop, but what the models show could lead to a temporary slow down that could allow something to develop.

[earthlight]

The 00z GFS changes are apparent as soon as 84 hours out from initialization. We all know what happens later, but here you can see the shortwave over the Southwest United States which was much weaker on the 18z. This traverses eastward and creates a broad trough over the Central US, which once the Greenland Ridging amplifies dramatically post 114 hrs, opens the door for a huge Polar Vortex phase.