December 24-25 Snowstorm

[dilly84]

The only thing Im saying is this. The gfs has been the only consistant model for this storm. The euro was north with the gfs until it decided to go south. Normally when the euro is correct, the gfs normally follows suit within a day or two. Not like this has been. The gfs isnt budging and neither is the euro. Canadian is starting to come around for the MW solution. Basically I am going to stick with the model that has been most consistant. This time that is the American.

[baroclinic_instability]

CAA? Unless I'm missing something the CAA doesn't seem overly impressive to me. Looks okay, but I don't see anything barbaric.

Nah I see what you are saying. An equatorward push of cold air in the low levels is hard to shift its direction. In other words, all models have a relatively deep push of low level cold air straight south, then the GFS tries to incite early cyclogenesis which rapidly changes the direction of the CAA from south towards the east coast. Possible yes, but from a pure cyclogenesis standpoint, it would need to be sufficiently strong, and therefore, would require the southern stream PV anomaly be strong enough when it phases with the northern stream. One trend worth noting with all global guidance is a weaker PV anomaly. If the PV is not strong enough, CAA will continue to dive towards the GOM. It can be shown through dynamical equations that low level CAA decreasing with height results in upper level height falls. In other words, this is how a trough "digs" southward. I find the much farther S models more realistic because they all develop the CAA farther S and therefore have a deeper digging trough. The PV Anomaly looks too weak to shift the CAA towards the east coast like the current GFS run does. Honestly, just an idea. We all know how all this can go...nobody knows for sure. Given a probability though...I would give the deeper south solutions a 75% chance of verifying, GFS at its position 25%.

[baroclinic_instability]

How does the Euro handle phasing? Do you find it to be better than the GFS and GGEM?

They actually all phase in a similar manner. It comes down to the strength of the PV Anomaly and how much cyclogenesis it supports. Read my early discussion I lay it out there. In short, I personally believe the PV will be too weak to sufficiently incite strong enough cyclogenesis to halt the equatorward motion of CAA eastward like the current GFS supports...which results in its much more northerly solution.

[Hoosier]

The only thing Im saying is this. The gfs has been the only consistant model for this storm. The euro was north with the gfs until it decided to go south. Normally when the euro is correct, the gfs normally follows suit within a day or two. Not like this has been. The gfs isnt budging and neither is the euro. Canadian is starting to come around for the MW solution. Basically I am going to stick with the model that has been most consistant. This time that is the American.

Consistency doesn't necessarily mean accuracy, but yeah, really a bit too early to "toss" anything.

[buckeye]

pretty soon this will be the new years eve storm. Lets see, ggem has a low heading out of the southeast up the coast at 120....im starting to wonder if us folks here in the ov should start rooting for the ggem and euro to begin a trend nw and turn this into an app runner, seems like there's plenty of time

i mean c'mon, a little earlier phase and this baby is riding the spine.....

[Chicago WX]

Consistency doesn't necessarily mean accuracy, but yeah, really a bit too early to "toss" anything.

Congrats on post #1000.

[cyclone77]

Nah I see what you are saying. An equatorward push of cold air in the low levels is hard to shift its direction. In other words, all models have a relatively deep push of low level cold air straight south, then the GFS tries to incite early cyclogenesis which rapidly changes the direction of the CAA from south towards the east coast. Possible yes, but from a pure cyclogenesis standpoint, it would need to be sufficiently strong, and therefore, would require the southern stream PV anomaly be strong enough when it phases with the northern stream. One trend worth noting with all global guidance is a weaker PV anomaly. If the PV is not strong enough, CAA will continue to dive towards the GOM. It can be shown through dynamical equations that low level CAA decreasing with height results in upper level height falls. In other words, this is how a trough "digs" southward. I find the much farther S models more realistic because they all develop the CAA farther S and therefore have a deeper digging trough. The PV Anomaly looks to weak to shift the CAA towards the east coast like the current GFS run does. Honestly, just an idea. We all know how all this can go...nobody knows for sure. Given a probability though...I would give the deeper south solutions a 75% chance of verifying, GFS at its position 25%.

Ahh, okay. Thanks for the explanation. Definitely makes sense. One thing to consider though, it seems like the models sometimes underplay the strength of such features in this range, only to tweak them stronger as they catch on later in the game. We've seen that a few times recently I think.

Just when we thought this thing was gonna be predictable, it throws all kinds of challenges at us LOL. I guess that's what makes this an addicting hobby.

[JoMo]

They actually all phase in a similar manner. It comes down to the strength of the PV Anomaly and how much cyclogenesis it supports. Read my early discussion I lay it out there. In short, I personally believe the PV will be too weak to sufficiently incite strong enough cyclogenesis to halt the equatorward motion of CAA eastward like the current GFS supports...which results in its much more northerly solution.

Hmm. Euro did come in stronger with it, and has it closed over Dallas, TX @ 96. The GGEM and GFS have already phased and are over the Ohio Valley region.

Is this just the Euro being slower with the phase?

[baroclinic_instability]

Ahh, okay. Thanks for the explanation. Definitely makes sense. One thing to consider though, it seems like the models sometimes underplay the strength of such features in this range, only to tweak them stronger as they catch on later in the game. We've seen that a few times recently I think.

Just when we thought this thing was gonna be predictable, it throws all kinds of challenges at us LOL. I guess that's what makes this an addicting hobby.

Totally agree, hence why I don't throw any solution out, haha. Nobody knows for certain just how strong that eventual PV anomaly in the southern stream will be, and my whole argument (and honestly, the way this likely will play out) hinges on the strength of that PV. I can only go off latest trends which suggests a slightly weaker PV than initially progged. This is a good example of how tiny differences (strength of the phasing PV) can result in overall massive forecast differences. Our lovely atmosphere is highly chaotic, and it goes to show how amazing it is we can even get close to forecasting 7 days out...sometimes even longer.

[wxdudemike]

i mean c'mon, a little earlier phase and this baby is riding the spine.....

If only...But I mean Henry at accuwx told me earlier I was gonna get hit hard so guess the Euro is wrong

[dilly84]

Hmm. Euro did come in stronger with it, and has it closed over Dallas, TX @ 96. The GGEM and GFS have already phased and are over the Ohio Valley region.

Is this just the Euro being slower with the phase?

basically what a lot of afd's have been saying, that the euro is too slow.

[baroclinic_instability]

Hmm. Euro did come in stronger with it, and has it closed over Dallas, TX @ 96. The GGEM and GFS have already phased and are over the Ohio Valley region.

Is this just the Euro being slower with the phase?

I see what you are saying...they all have a rather "weak" migratory PV anomaly, and it seems not a very deep or intense one. The ECMWF has a pretty weak one overall over Texas.

[dilly84]

From KPIT

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...

-- Changed Discussion --VARIOUS MODELS CONTINUE TO FORECAST THE DEVELOPMENT OF A HIGH

AMPLITUDE EASTERN CONUS TROUGH FOR THE HOLIDAY WEEKEND. THE

CRITICAL MID LEVEL LOW PROGNOSIS IS NOT AS CONSISTENT IN THE

GFS/ECMWF SOLUTIONS AS IN RECENT DAYS, BUT ACCUMULATING SNOW IS

STILL A FAIR BET AND WILL THUS CONTINUE TO HIGHLIGHT IN THE

HAZARDOUS WEATHER OUTLOOK.

THE DEVELOPING PATTERN CAN ONLY REINFORCE THE COLD TEMPERATURES

WHICH HAVE PLAGUED THE EAST FOR THE PAST MONTH.

[baroclinic_instability]

Dilly makes a good point and a southern or northern solution really doesn't matter a ton since snow will likely develop over much the same areas. It won't be as heavy if a southern solution verifies, but all solutions have snow with the initial phase across much of the OV. I am really quite interested in if this coastal develops, and how strong. Will be a fun forecast to watch. A southern solution supports a potential east coast crippler if the timing is right.

[dilly84]

Dilly makes a good point and a southern or northern solution really doesn't matter a ton since snow will likely develop over much the same areas. It won't be as heavy if a southern solution verifies, but all solutions have snow with the initial phase across much of the OV. I am really quite interested in if this coastal develops, and how strong. Will be a fun forecast to watch. A southern solution supports a potential east coast crippler if the timing is right.

Im like Buckeye, if the Euro is going to be slower, might as well get a phase sooner and a nw trend and make this an apps runner lol. Low position is a major difference in the GFS and the ECMWF, but another big difference is the euro seems much weaker. coming across, while the gfs isnt a monster over the OV, it still spits out .5 - .75 over the 60hr period, where the Euro isnt even close to that.

Fact of the matter is this, I would think this mystery will be solved no sooner than Wednesday 12z runs. Either the GFS or the Euro has to budge.

[JoMo]

Dilly makes a good point and a southern or northern solution really doesn't matter a ton since snow will likely develop over much the same areas. It won't be as heavy if a southern solution verifies, but all solutions have snow with the initial phase across much of the OV. I am really quite interested in if this coastal develops, and how strong. Will be a fun forecast to watch. A southern solution supports a potential east coast crippler if the timing is right.

Means a ton for my area tho (SW Missouri). GFS is 35 and rain while the Euro would probably be colder due to the low being farther south. Of course the Euro probably doesn't put out as much QPF up here. It's going to be Christmas and I haven't seen a flurry yet so I'm getting antsy.

[dilly84]

Means a ton for my area tho (SW Missouri). GFS is 35 and rain while the Euro would probably be colder due to the low being farther south. Of course the Euro probably doesn't put out as much QPF up here. It's going to be Christmas and I haven't seen a flurry yet so I'm getting antsy.

Last White Christmas I remember was in 1995. May have been one for mby since then, but not that I can remember. 04 was all ice here.

[JoMo]

Last White Christmas I remember was in 1995. May have been one for mby since then, but not that I can remember. 04 was all ice here.

We had one last year. If temps are just a little colder we may have one again, even on the GFS, going to be a close call.

00z Ensemble @ 102

[dilly84]

We had one last year. If temps are just a little colder we may have one again, even on the GFS, going to be a close call.

Well good luck. It'd be nice if we all got to share in a white Christmas. The little bit of snow I have left outside will be gone tomorrow. 1/4" lol

[JoMo]

06z NAM = Stronger, closed, wetter.

Line of Thunder-snow/ice or something in the cold air forming along that intense VV, heh

[Omahawx]

Wow if the models couldnt have gotten any worse for me..the latest nam barely gives me .10 when just 24 hours ago they were having me .50-.75

[dilly84]

Well at least 12z I should be able to see what its going to do here on the nam.

[jcwxguy]

Wow if the models couldnt have gotten any worse for me..the latest nam barely gives me .10 when just 24 hours ago they were having me .50-.75

yeah, no kidding right there is still time..

[dilly84]

yeah, no kidding right there is still time..

Yea. Wouldn't worry too much about the nam yet. Need to get the track down first lol.

[Omahawx]

Yeah there has been an overall trend late in the game for the storms to suddenly shift north on the models..one can only hope

[dilly84]

Yeah there has been an overall trend late in the game for the storms to suddenly shift north on the models..one can only hope

At this point I am just hopeful the GFS is right. It has increased qpf for ohio 4 consecutive runs.

[jcwxguy]

so far at hour 30, the 6gfs is farther north on the coast on cali

but a hour 42, its the same spot

[dilly84]

so far at hour 30, the 6gfs is farther north on the coast on cali

but a hour 42, its the same spot

May be a Tad north at 54

[jcwxguy]

06z gfs looks good for you omahawx

[JoMo]

Well it's a quicker phase this run. Strangely a little slower at the surface @ 96 and the vort is farther south.