December 18-20 Potential Talking Points

[Allsnow]

Classic setup for classic let-down. Honestly I believe this looks good, and the best chance we've had so far this winter (although just the beginning) for some good snow. 4-5 days out yet, but good signals at least. Someone will probably get good snow, someone will probably get screwed. The nature of the beast.

Well like you said thats the nature of the beast. We are not dealing with a juice up southern jet with all this moisture up front........Just think about March 2009 storm

[NEG NAO]

Looks like a 50-75 mile shift east with the low/precip shield.

Heck of a run for long island though...

Not just long island - anyone east of the PA/NJ state line gets a MECS according to the 18Z - amounts decrease every mile west of there...

[_AR_]

miller B is a classic set-up for a screw job---this will likely have a sharp cutoff but not anything like a miller B...this is unless this is an IMBY statement and then this is just a dumb post

No, I think it's pretty realistic. What is the probability of a good snowstorm showing up on the models 5 days out and playing out like you want it to? This is the best shot we've had so far this season though, by far, I'm not denying that. Surface and 500mb look good on the GFS at least as of now. Hopefully nothing jumps ship on us.

Regardless, potential for big snowstorm -> time for excitement and drama -> time for me to read only red-tag posts I guess.

[Kaner587]

No, I think it's pretty realistic. What is the probability of a good snowstorm showing up on the models 5 days out and playing out like you want it to? This is the best shot we've had so far this season though, by far, I'm not denying that. Surface and 500mb look good on the GFS at least as of now. Hopefully nothing jumps ship on us.

Regardless, potential for big snowstorm -> time for excitement and drama -> time for me to read only red-tag posts I guess.

I will never for the life of me understand why people on these boards take what you say and swing it to make their post make sense. The only point I made is a screw job is a GUARANTEE in a miller B and while this storm, if it even happens, will have a sharp cutoff it is nothing like the worst case scenario would be. Please don't put words in my mouth.

[Edge Weather]

18Z NOGAPS gets so deep near the the Benchmark that I can't tell how deep it is. Looks like about 959mb.

[forkyfork]

the gfs has a known bias for being too aggressive with the polar jet. especially in la ninas. in this case, it means over phasing with the system in the southern us and showing everyone a fantasy snowstorm

[Sundog]

Is the GFS 18z se bias still in effect or did they resolve that issue?

[Kaner587]

the gfs has a known bias for being too aggressive with the polar jet. especially in la ninas. in this case, it means over phasing with the system in the southern us and showing everyone a fantasy snowstorm

and at 12z it was mostly southern stream when it had a similar track and QPF output...must be the same problem huh?

In fact, people were arguing that it almost didn't phase at all, but I think the consensus was partial phase

[rossi]

the gfs has a known bias for being too aggressive with the polar jet. especially in la ninas. in this case, it means over phasing with the system in the southern us and showing everyone a fantasy snowstorm

Is that the case with all the other models showing a snowstorm?

Rossi

[earthlight]

It's still the shortwave diving southeast from the Rockies that is helping the broad trough amplify rapidly over the southeast United States. The GFS has had this feature for five runs in a row now and has been varying with the strength of confluence over the northeast--but three runs have shown a snowstorm. The orientation of the 250-300mb jet stream and upper level heights are very favorable for a big coastal low if this shortwave over the Rockies is real. The NAM caught on to this feature on the 18z run as well--hence the DGEX coming straight up the coast once that feature gets into the trough. You can see it at 90 hours and then the link to 102 hours is below when the feature has phased in.

http://www.meteo.psu.edu/~gadomski/AVN_18z/f102.gif

[SnowGoose69]

18Z NOGAPS gets so deep near the the Benchmark that I can't tell how deep it is

Thats a positive sign again,...seeing the NOGAPS more like the Euro than the GFS as far as how east the surface low is positioned is a good sign for sure.

[Kaner587]

do you even know what level to look at to identify the subtropical jet?

it's not 500mb...

I'm not arguing with your analysis but if you're going to say its overphasing this go round, fine, but then you're going to have to explain the diff evolution at 12z that still results in a big storm, without overphasing, as you put it. And interestingly enough, that midwest storm was underphased by the GFS, not saying it doensn't have the bias though just giving a recent example.

[forkyfork]

300mb

wrong.

any semblance of the subtropical jet is north of puerto rico... not near our storm system

[Kaner587]

so are you saying that DT et al are lying, there is no southern stream involvement lol??

[SnowGoose69]

I just got home and saw the Euro....I'll say the one thing I do not like and this may be a surprise to everyone is that based on the orientation of the PV and trough at 500mb from Canada south to the Carolinas at 120 hours...if the low does indeed get better captured it could very well come straight north up the coast which could result in changeover issues.

[forkyfork]

so are you saying that DT et al are lying, there is no southern stream involvement lol??

the main player is the polar jet... the storm happens on the gfs because the displaced polar vortex phases with a short wave coming out of the rockies

[snywx]

I just got home and saw the Euro....I'll say the one thing I do not like and this may be a surprise to everyone is that based on the orientation of the PV and trough at 500mb from Canada south to the Carolinas at 120 hours...if the low does indeed get better captured it could very well come straight north up the coast which could result in changeover issues.

Might be the only way inland areas get in on the action...

[ORH_wxman]

so are you saying that DT et al are lying, there is no southern stream involvement lol??

Southern stream and STJ are often intertwined even if the southern stream is not the STJ...which it isn't this time, but its essentially replacing the STJ in this setup....since the polar jet is split in part of it rides south in the US.

So while you may hear "the STJ is not phasing this run"...its really "the southern stream is not phasing"...but its the same difference. Its not the pineapple express STJ you see in Ninos though.

[Edge Weather]

Interesting, thanks for the info.

I just got home and saw the Euro....I'll say the one thing I do not like and this may be a surprise to everyone is that based on the orientation of the PV and trough at 500mb from Canada south to the Carolinas at 120 hours...if the low does indeed get better captured it could very well come straight north up the coast which could result in changeover issues.

[Stormlover74]

There usually are prepcipation type issues so wouldn't surprise me. It could be a case of us wanting it to come west and then it being too far west

[quote

name=SnowGoose69' timestamp='1292366789' post='109039]

I just got home and saw the Euro....I'll say the one thing I do not like and this may be a surprise to everyone is that based on the orientation of the PV and trough at 500mb from Canada south to the Carolinas at 120 hours...if the low does indeed get better captured it could very well come straight north up the coast which could result in changeover issues.

[Kaner587]

Southern stream and STJ are often intertwined even if the southern stream is not the STJ...which it isn't this time, but its essentially replacing the STJ in this setup....since the polar jet is split in part of it rides south in the US.

So while you may hear "the STJ is not phasing this run"...its really "the southern stream is not phasing"...but its the same difference. Its not the pineapple express STJ you see in Ninos though.

thank you someone willing to teach much appreciated ORH

[snywx]

That is so similiar to last year 12/19

Rossi

Not a fond memeory for areas NW of NYC

[earthlight]

The 18z GFS Ensemble means are much further southeast and less amplified than the OP, and also much less amplified compared to the 12z ensembles.

[Jefflaw77]

The 18z GFS Ensemble means are much further southeast and less amplified than the OP, and also much less amplified compared to the 12z ensembles.

well that sux... On to the 00z - see you all tonite..

[NEG NAO]

The 18z GFS Ensemble means are much further southeast and less amplified than the OP, and also much less amplified compared to the 12z ensembles.

Here we go again - first indication the 0Z GFS OP will be trending east ?? ??

[Dsnowx53]

The Euro is actually a lot more aggressive with the northern stream penetrating southward than the GFS is...the GFS just has a much stronger southern stream than the Euro, and thus a snowier solution.

[billgwx]

The 18z GFS Ensemble means are much further southeast and less amplified than the OP, and also much less amplified compared to the 12z ensembles.

As they often have been in the past for coastal storms.

[phlwx]

It's still the shortwave diving southeast from the Rockies that is helping the broad trough amplify rapidly over the southeast United States. The GFS has had this feature for five runs in a row now and has been varying with the strength of confluence over the northeast--but three runs have shown a snowstorm. The orientation of the 250-300mb jet stream and upper level heights are very favorable for a big coastal low if this shortwave over the Rockies is real. The NAM caught on to this feature on the 18z run as well--hence the DGEX coming straight up the coast once that feature gets into the trough. You can see it at 90 hours and then the link to 102 hours is below when the feature has phased in.

There are huge differences at 500 mb in Canada...it's not even funny. There's a much broader, deeper trough at the mid levels on the ECM that essentially suppresses and blocks any northward movement of storms, thus preventing the southern stream from phasing in quickly. The GFS has less blocking and allows for the amplification and resulting phase and track up the coast.

[Kaner587]

As they often have been in the past for coastal storms.

so Bill what are you're thoughts?

[ORH_wxman]

The Euro is actually a lot more aggressive with the northern stream penetrating southward than the GFS is...the GFS just has a much stronger southern stream than the Euro, and thus a snowier solution.

They are basically flipped in which stream is stronger...the Euro is much more bullish in penetrating the northern stream southwest into and beyond the Lakes....while the GFS is quite weak there...and the GFS is more robust with the southern stream and the Euro not as much...so essentially you get:

GFS - Weaker northern stream and stronger southern stream allows amplification much easier and the eventual phase on the 18z happens with relative ease.

Euro - More overbearing northern stream and weaker southern stream makes it difficult for the southern stream to gain any latitude and amplification until it has finally rounded the base of the northenr stream dominant s/w....by that point, its nearly at the coastline and you see a storm that stays mostly offshore.

Euro has been very consistent with its stronger northenr stream depiction while the GFS has been screwing around with that setup for many runs....so I know which one I'm inclined to lean towards. That said, it wouldn't take much of a difference to get the Euro into a big storm for a lot of areas. Phase it about 6 hours sooner and it will take a pretty fast left turn up the coast. A lot of things could cause that to happen...Euro goes slightly faster with southern stream energy....or maybe it extends the northern stream even further s/w as to start the phase sooner....or maybe its weaker in the northern stream enough to allow southern to gain some latitude. A lot of things to watch. But I'm certainly leaning more toward the Euro depiction of the N stream at the moment.