December Discussion Thread

[SnowGoose69]

I didn't see the 00Z GFS ensembles yet but the NOGAPS is even further west at 42-48 hours than the Op GFS was tonight, the GGEM was fairly similar to the RGEM and the UKMET was farther west as well...will have to see what the Euro does but right now the Op GFS is an outlier being too far east based on the placement of all the other models...still need plenty of help though unless you're on LI.

[Absolute Humidity]

NOGAPS rule. Long range GFS has a steady diet clipper redevelopers effecting mostly SNE. Gonna be tough to get decent snows in here as depicted.

[mob1]

19 degrees in NYC, finally.

[Guest Pamela]

Seasonal Snowfall

2013-14 Winter

As of 12/25/2013 / 4:30 AM

Worcester: 18.6"

Allentown: 13.1"

Hartford: 12.4"

Boston: 11.4"

Philadelphia Intl. Airport: 11.2"

Bridgeport / Sikorsky: 10.9"

Newark Airport: 9.4"

NYC Central Park: 8.6"

Islip, NY: 8.4"

NYC LaGuardia: 7.8"

Providence: 7.1"

NYC JFK: 6.9"

Washington Dulles: 4.7"

Atlantic City: 3.3"

Baltimore (BWI): 2.9"

Washington National: 1.5"

[bluewave]

The two December -EPO snow months above 6" at NYC of 1990 and 2008 featured very similar

seasonal snowfall totals of around 25".

1990-91  0    0    0    0    0    7.2   8.4   9.1   0.2    0    0    0    24.9

2008-09  0    0    0    0    T    6.0   9.0   4.3   8.3    T    0    0    27.6

 

 

 

[PB GFI]

I wrote yesterday that the Euro Precip shield looked too tight for a deepening system coming off Hatteras heading the the BM .

I said I thought this was an interior storm threat .  Areas from NEPA NWNJ and the lower Hudson Valley temps never get above 34 Degrees   hr 102- hr 108 .

Will take a few days to get sorted , but that's the area to watch .  

[Storm At Sea]

That would not be an inland storm...late dec with storm offshore...temps will come around in our favor...looks likes a secs

[PB GFI]

That would not be an inland storm...late dec with storm offshore...temps will come around in our favor...looks likes a secs

I hear you , but I don't like the Surface temps being progged on this run .  Its coming NE  after the trough has pulled back for 2 days  , then it becomes a race

for the 850s to get back to the coast . As it is surface temps are in the upper 30`s around the city , so its nor far off .

But I think its better to go inland threat 1st if it trends our way then great .

Its just not there yet .

[UlsterCountySnowZ]

Merry Christmas all!!!! What's the time frame of the possible storm being discussed?

[HailMan06]

Merry Christmas all!!!! What's the time frame of the possible storm being discussed?

Next one I'm seeing is around January 3rd.

[mob1]

Next one I'm seeing is around January 3rd.

The one being discussed here is for 12/29, it looks like either a miss or rain verbatim on the models but things can change.

[Weathergun]

That would not be an inland storm...late dec with storm offshore...temps will come around in our favor...looks likes a secs

 

There's another low over the Eastern Lakes.

[wolfsheepsheadbay]

That would not be an inland storm...late dec with storm offshore...temps will come around in our favor...looks likes a secs

What? Please explain.

[Hailstorm]

Looking at Upton's 7-day forecast for NYC, one wouldn't think that an arctic blast is coming for next week. In fact, it looks like a semi-torch for us. If those predicted temps come to fruition, we'd likely finish December with a +1 monthly departure despite the first part of the month being so cold. I don't like seeing how this weeks' temps keep on getting bumped up day after day. It doesn't bode well for us in January if the models keep on doing this; thus, I wouldn't be surprised if next week's "frigid blast" doesn't end up any colder than today's low of 19 degrees and a high in the 20s for only one day.

[REDMK6GLI]

What? Please explain.

If the storm deepens enough and track is far enough off the coast i cant why it cant pull down more cold air from canada. Gotta iron out the details still but i can see this trending everyones way for sure

[earthlight]

That would not be an inland storm...late dec with storm offshore...temps will come around in our favor...looks likes a secs

 

Could not disagree any more. You must not really be looking at the model at all. It takes 3 seconds to see that the antecedent airmass is warm.

[SnowGoose69]

The one being discussed here is for 12/29, it looks like either a miss or rain verbatim on the models but things can change.

 

Yeah, IMO there is no way this is a snow event, it either misses or its rain, there really is no way to get the cold air in and also get the storm to get close enough for snow

[earthlight]

If the storm deepens enough and track is far enough off the coast i cant why it cant pull down more cold air from canada. Gotta iron out the details still but i can see this trending everyones way for sure

 

The only way that happen is if the big northern stream energy associated with the polar vortex digs farther south and captures the southern stream vort -- in which case it would get tugged inland anyway. This is the kind of setup where you need high latitude blocking to increase your chances of getting snow -- and we don't have any.

[Weathergun]

We had similar threat the end of December of last year. That had deep low off the coast. But also an inland low that remained. It was mostly rain. This one has even less cold air in front it.

[PB GFI]

The only way that happen is if the big northern stream energy associated with the polar vortex digs farther south and captures the southern stream vort -- in which case it would get tugged inland anyway. This is the kind of setup where you need high latitude blocking to increase your chances of getting snow -- and we don't have any.

The way the GFS and Euro Control show it , is its 850`s are  plus 3 at 120 hrs on a W wind  in NWNJ Lower HV NEPA Cent CT and temps max out at 35 .

The precip shield sould b bigger if its Hatteras to Cape Cod ,  They are only a step away , ( 6 hours slower ) on arrival time as the trough comes back SE .

I DONT thnk this is a coastal threat , but 287 - 80 and points N  and NE ,there could be some  frozen there . D5 so lets see if the inland guys can have it trend better

[PB GFI]

We had similar threat the end of December of last year. That had deep low off the coast. But also an inland low that remained. It was mostly rain. This one has even less cold air in front it.

Yeh , 850`s were minus 2   surface was 33 on the north shore  of LI , but at 925 mb winds were E , as the center didn't close off , and it was a cold rain

but remember central CT got a ft of snow with that

[REDMK6GLI]

The only way that happen is if the big northern stream energy associated with the polar vortex digs farther south and captures the southern stream vort -- in which case it would get tugged inland anyway. This is the kind of setup where you need high latitude blocking to increase your chances of getting snow -- and we don't have any.

Point taken john i see what your saying. Bottom line atleast we've had some action this month anyway

[earthlight]

The way the GFS and Euro Control show it , is its 850`s are  plus 3 at 120 hrs on a W wind  in NWNJ Lower HV NEPA Cent CT and temps max out at 35 .

The precip shield sould b bigger if its Hatteras to Cape Cod ,  They are only a step away , ( 6 hours slower ) on arrival time as the trough comes back SE .

I DONT thnk this is a coastal threat , but 287 - 80 and points N  and NE ,there could be some  frozen there . D5 so lets see if the inland guys can have it trend better

 

As currently modeled I don't think it's very close at all. This is several steps away from being a snowstorm. I'll clarify: it may be a few steps away from some frozen precipitation across the interior, but it is several steps away from anything of significance.

 

The initial low pressure system moves northeast through the Great Lakes into New England and this induces a warm southwest flow to the south of it both in the low and mid levels. The southern stream vort is still very far detached from the northern stream and associated cold air which is still located over the Northern Plains. So while this southern stream energy can move northeast and track along a conveniently placed baroclinic zone, the northern stream energy and height falls will continue to track east/southeast.

 

This is where the depth and amplification of the northern stream comes into play. High latitude blocking typically forces these polar entities and northern stream shortwaves farther south in latitude -- and helps to amplify the pattern over much of the United States' eastern 1/3. If you recall an event in January 2011 which was initially modeled to be warm -- the models all trended colder at all levels. This was not coincidence; it was due to the guidance picking up on the fact that the northern stream would be forced southward and the cold air would be forced to re-establish itself over the Northeast US as a result of the blocking high to the north.

 

We do not have a mechanism to cause such a process and in this case having that low pressure area track through New England is a death sentence to most areas. Sure, there could be a period of frozen precipitation in the mountains and far interior. But in this setup, as modeled currently, nobody is going to receive anything of significance simply because the antecedent cold air is nonexistent and the lack of high latitude blocking will rear its ugly head.

 

[Heisy]

As currently modeled I don't think it's very close at all. This is several steps away from being a snowstorm. I'll clarify: it may be a few steps away from some frozen precipitation across the interior, but it is several steps away from anything of significance.

 

The initial low pressure system moves northeast through the Great Lakes into New England and this induces a warm southwest flow to the south of it both in the low and mid levels. The southern stream vort is still very far detached from the northern stream and associated cold air which is still located over the Northern Plains. So while this southern stream energy can move northeast and track along a conveniently placed baroclinic zone, the northern stream energy and height falls will continue to track east/southeast.

 

This is where the depth and amplification of the northern stream comes into play. High latitude blocking typically forces these polar entities and northern stream shortwaves farther south in latitude -- and helps to amplify the pattern over much of the United States' eastern 1/3. If you recall an event in January 2011 which was initially modeled to be warm -- the models all trended colder at all levels. This was not coincidence; it was due to the guidance picking up on the fact that the northern stream would be forced southward and the cold air would be forced to re-establish itself over the Northeast US as a result of the blocking high to the north.

 

We do not have a mechanism to cause such a process and in this case having that low pressure area track through New England is a death sentence to most areas. Sure, there could be a period of frozen precipitation in the mountains and far interior. But in this setup, as modeled currently, nobody is going to receive anything of significance simply because the antecedent cold air is nonexistent and the lack of high latitude blocking will rear its ugly head.

 

no.png

 

Yep, great explaining...If we could all just ignore the weather until after New Years we'd all be happier. The threats start then. 

[Storm At Sea]

I would have expected more from you. Dissecting a single run of the gfs? Taking it literally? Use your experience.

As currently modeled I don't think it's very close at all. This is several steps away from being a snowstorm. I'll clarify: it may be a few steps away from some frozen precipitation across the interior, but it is several steps away from anything of significance.

 

The initial low pressure system moves northeast through the Great Lakes into New England and this induces a warm southwest flow to the south of it both in the low and mid levels. The southern stream vort is still very far detached from the northern stream and associated cold air which is still located over the Northern Plains. So while this southern stream energy can move northeast and track along a conveniently placed baroclinic zone, the northern stream energy and height falls will continue to track east/southeast.

 

This is where the depth and amplification of the northern stream comes into play. High latitude blocking typically forces these polar entities and northern stream shortwaves farther south in latitude -- and helps to amplify the pattern over much of the United States' eastern 1/3. If you recall an event in January 2011 which was initially modeled to be warm -- the models all trended colder at all levels. This was not coincidence; it was due to the guidance picking up on the fact that the northern stream would be forced southward and the cold air would be forced to re-establish itself over the Northeast US as a result of the blocking high to the north.

 

We do not have a mechanism to cause such a process and in this case having that low pressure area track through New England is a death sentence to most areas. Sure, there could be a period of frozen precipitation in the mountains and far interior. But in this setup, as modeled currently, nobody is going to receive anything of significance simply because the antecedent cold air is nonexistent and the lack of high latitude blocking will rear its ugly head.

 

no.png

[MJO812]

Could not disagree any more. You must not really be looking at the model at all. It takes 3 seconds to see that the antecedent airmass is warm.

Yes on this model. We know that the solutions can change. If the storm blows up, that will bring down colder air which will mean a colder solution.

[earthlight]

I would have expected more from you. Dissecting a single run of the gfs? Taking it literally? Use your experience.

 

 

I used the GFS run for an illustration and I specifically stated "as currently modeled" several times in my post. Just to tickle your fancy...lets break it down on some other guidance.

 

Here's the Canadian, which shows a very similar setup. As on the GFS, we can see the southern stream vorticity detached from the main cold air supply. The lead shortwave over Southeast Canada has spawned a low pressure system just over the International Border north of NY State. Southwest flow in the mid and low levels has scoured out any cold air which was present. 850mb temperatures are over +10 C in Cape May. The northern stream trough is still back over the Northern Plains. As this drops southward it will bring colder air with it, but the southern stream vorticity will scoot along the baroclinic zone to the north and east. If, for the sake of argument, the northern stream shortwave were to dramatically amplify to the south, it would tug the southern stream vort and associated low pressure inland, bringing warm air with it.

 

 

Now, we can analyze last nights 00z Euro. We can even see a slightly different solution here, but again it draws back to the basics of the setup. On the Euro, the southern stream vorticity is pushed farther to the south and east and the baroclinic zone in shunted offshore. The northern stream vorticity is a bit faster, but not more amplified -- i.e, it will push the height field farther south and east while bringing cold air with it, but will also take the precipitation shield and flatten it as it doesn't allow for expansion of moisture on the NW side due to the developing W/NW flow there.

 

This scenario seems perfectly viable as well, but again provides minimal to no chances for frozen precipitation. As you can see, the polar vortex has become a giant gyre on the Euro and all other models, The northern stream shortwave we are tracking is, in essense, the far southerly extent of this polar vortex. In order for it to amplify further, we would need either a big PNA spike out west (which we don't have) or high latitude blocking to force it underneath (which we don't have).

 

 

And finally, we can glance at the GEFS ensembles which show you a variety of solutions (this way, I am not looking at one singular GFS run as you seem to believe) and options. We can see more amplified solutions with the southern stream vorticity closer to the coast, ones closer to the GFS and CMC with the surface low on a well placed baroclinic zone offshore, and ones which are less amplified and keep the surface low farther to the south and east. None of them provide any chance for a SECS as you mentioned earlier.

 

http://www.meteo.psu.edu/~fxg1/ENSPRSNE_12z/f108.gif

 

Here's the bottom line, at least in my opinion. As modeled currently (on all guidance and ensembles), this setup stinks. There is no cold air, a low pressure system moves through the Great Lakes, and the southern stream entity is detached from any northern stream or PV interaction. Could the modeled setup change dramatically and give us a chance for snow? Sure. But right now, the advertised pattern leaves a lot to be desired in this specific time frame. I am much more encouraged about potential thereafter--into the first week of January.

[earthlight]

Yes on this model. We know that the solutions can change. If the storm blows up, that will bring down colder air which will mean a colder solution.

 

That premise is incorrect and too easy to say and throw around. If this storm blows up, it will be because it's phasing or being tucked inland due to interaction with the incoming northern stream vorticity. That would mean that the northern stream would have to amplify fairly dramatically in the current pattern. That would be encouraging for a deeper low pressure system/etc but it would also bring in warmer air -- because there is no blocking in the high latitudes to force a high pressure underneath it into Southeast Canada. So in a sense, it's a lose-lose situation. I've seen a lot of things in meteorology, but I would be really *really* shocked if this storm brought significant snow to anyone but the far interior locations of the Northeast or New England. 

[earthlight]

The Canadian is hinting at the potential for something much more favorable immediately following the 12/30-1/1 setup. Here's a shortwave cutting underneath a well established cold air mass which extrapolated would probably bring a moderate snow event.

 

http://www.meteo.psu.edu/~fxg1/CMC_12z/f180.gif

[PB GFI]