12z Model Thread 12/14/10

[blazess556]

12z GGEM way out to sea

[baroclinic_instability]

Maybe not that cold by Minnesota standards...

Well that is true, but really not that cold for east coast coastals either.

[SnowGoose69]

What's the deal with the models lately? They are all over the place. We seen this with the last storm too.

Its likely right now the GFS is just wrong...I do not remember many cases where the GFS shows a coastal bomb, especially with that upper level setup and the GEM is that far out to sea

[Guest someguy]

So what you're saying is,

Correct me if I'm wrong...

The GFS has not moved towards the initial solution of the EURO from the weekend that caused all the excitement.

It has found it's own solution that has a similar result.

yes

[TUweathermanDD]

Its likely right now the GFS is just wrong...I do not remember many cases where the GFS shows a coastal bomb, especially with that upper level setup and the GEM is that far out to sea

Ukmet was like the gfs at 0Z last night though right?

[buckeye]

you guys should check out the 500 maps of the 12z gfs, ggem, and ukie at 72 hours....the differences are amazing

I bet the 12z ukie comes in with a full phase because it has a close 500 over MN looking like it's going to drop in. The ggem has nothing and the gfs has a much smaller one further nw.

[Dsnowx53]

Some of you guys are acting like the southern stream just got strong and negatively tilted all by itself, which is not true.

As earthlight pointed out, it phased with a shortwave that dropped into Montana/Utah, and that's what really got our southern stream energy going. All it needed was the PV to split, and the confluence that was over Maine to move NE, and that's what we got.

[Baroclinic Zone]

Its likely right now the GFS is just wrong...I do not remember many cases where the GFS shows a coastal bomb, especially with that upper level setup and the GEM is that far out to sea

12z GFS Ens. mean is about 100mi SE of the BM.

[WhiteoutWX]

Its going to Bermuda based on the 84 hour prediction unless something really changes from then til 108.

It looks to me it is all based on the placement of the closed vortex in SE Canada, as well as two small shortwaves moving through the northern plains, and then the southern wave. The GFS has the vortex far enough east/north to allow amplification as the southern wave nears the East coast, as well as emphasizing the trailing northern shortwave, and damping out the one in front. This weak northern stream impulse then drops into the southern wave by hr 96 (so some phasing does occur early), producing a rapid sharpening of the trough as it comes east. GGEM on the other hand emphasizes the front northern stream wave, and has a stronger, further west vortex. These both act to damen out the southern stream energy, not allowing it to amplify. Subtle differences in handling all these pieces means everything.

[stormtracker]

Like I said, I'm kinda leery of the GFS at this stage, especially with the GGEM heading seaward like it did. If the UK/Euro get on board, I'd have a lot more confidence with this thing

[SnowGoose69]

The GEM being that progressive is as bad as the NOGAPS being over Portugal on its 12Z run (I don't see the 12Z NOGAPS yet) but I'll tell you right now...the GEM is about as bizarro to its normal bias as it could be on this 12Z run...the NOGAPS is normally progressive so I'd be shocked if its not a miss on the 12Z run but we don't want to see it be too much of a miss....I'd like to see it at least take the center of the low NE off the Carolinas...if there is a sharp ENE or E movement we're not looking good, just based off the typical model bias frame of mind.

[Guest someguy]

Some of you guys are acting like the southern stream just got strong and negatively tilted all by itself, which is not true.

As earthlight pointed out, it phased with a shortwave that dropped into Montana/Utah, and that's what really got our southern stream energy going. All it needed was the PV to split, and the confluence that was over Maine to move NE, and that's what we got.

Um not not quite.

earhtlight is right... there isa phase between the southern stream s/w and the s/w over UT.

so there is that..

BUT that is NOT the same thing as the as the a peice of PV coming south and phasing

[Dsnowx53]

It looks to me it is all based on the placement of the closed vortex in SE Canada, as well as two small shortwaves moving through the northern plains, and then the southern wave. The GFS has the vortex far enough east/north to allow amplification as the southern wave nears the East coast, as well as emphasizing the trailing northern shortwave, and damping out the one in front. This weak northern stream impulse then drops into the southern wave by hr 96, producing a rapid sharpening of the trough as it comes east. GGEM on the other hand emphasizes the front northern stream wave, and has a stronger, further west vortex. These both act to damen out the southern stream energy, not allowing it to amplify. Subtle differences in handling all these pieces means everything.

Very good post.

[Ridingtime]

missing the point totoally

a full, pjhase pulls this Low up the coast

that is what the minster euro rusn were showing last weekend

this 12z gfs does NOT do this at all

this is PURE southern stream or the STJ energy going severely negative

period

there severe negative tilt of the s/w captures the Low and pulls it North SOME

not all the way

I do understand that a full phase allows the thing to go up the coast, but can you please explain to me why can't that happen without the phase? If you look at the 500mb Vort maps comparing the 6z GFS to the 12z there is a noticeable difference in the split of the PV. In the 6z the PV does not split enough and just elongates preventing the storm from moving up, whereas with the 12z it splits way more forming two separate lobes and allowing a direct path upward between the gap for the storm up the coast. This can happen without a phase. But if I am missing something please explain.

[Dsnowx53]

Um not not quite.

earhtlight is right... there isa phase between the southern stream s/w and the s/w over UT.

so there is that..

BUT that is NOT the same thing as the as the a peice of PV coming south and phasing

Oh yeah, it's certainly not the same thing. But that phase with that s/w over Utah did a lot to amplify our southern stream shortwave, so it's not outlandish that the GFS became so amplified and negatively tilted, despite the piece of the PV not dropping in, IMO.

[buckeye]

Like I said, I'm kinda leery of the GFS at this stage, especially with the GGEM heading seaward like it did. If the UK/Euro get on board, I'd have a lot more confidence with this thing

i think the ukie jumps on board for you big time.

[baroclinic_instability]

It looks to me it is all based on the placement of the closed vortex in SE Canada, as well as two small shortwaves moving through the northern plains, and then the southern wave. The GFS has the vortex far enough east/north to allow amplification as the southern wave nears the East coast, as well as emphasizing the trailing northern shortwave, and damping out the one in front. This weak northern stream impulse then drops into the southern wave by hr 96 (so some phasing does occur early), producing a rapid sharpening of the trough as it comes east. GGEM on the other hand emphasizes the front northern stream wave, and has a stronger, further west vortex. These both act to damen out the southern stream energy, not allowing it to amplify. Subtle differences in handling all these pieces means everything.

Yeah pretty much. It is pretty much a "partial" triple-phase event. Throw in it really isn't all that cold in the low levels and everything needs to come together perfectly. Threading the needle. I still stick with a 15% chance this storm develops and crushes the coast.

[Dsnowx53]

Snowgoose, the NOGAPS came in much further west than last night. Still not a hit, but significant improvements:

https://www.fnmoc.navy.mil/wxmap_cgi/cgi-bin/wxmap_single.cgi?area=ngp_namer&dtg=2010121412∏=thkτ=132&set=Core

[Atlas]

12z UKIE @ 72 HOURS would imply a big hit imo...

http://vortex.plymouth.edu/cgi-bin/gen_grb-comp.cgi?re=namer&mo=ukmet&va=c500&ft=h72&cu=latest≥=800x630&ti=UTC&id=&zoom=.6

[Nor Easter]

i think the ukie jumps on board for you big time.

Yep I agree, UKMET is going to show a serious coastal bomb.

-Nor

[baroclinic_instability]

I do understand that a full phase allows the thing to go up the coast, but can you please explain to me why can't that happen without the phase? If you look at the 500mb Vort maps comparing the 6z GFS to the 12z there is a noticeable difference in the split of the PV. In the 6z the PV does not split enough and just elongates preventing the storm from moving up, whereas with the 12z it splits way more forming two separate lobes and allowing a direct path upward between the gap for the storm up the coast. This can happen without a phase. But if I am missing something please explain.

The northern vortex where all the cold air is doesn't magically split. You bring up a good question though. As Earthlight and others have said, that first wave over UT/MT is key as it enhances the upper level baroclinic zone/upper level front. ONce the final phase develops with the northern vortex, this PV Anomaly is stronger due to the enhanced phase with the UT/4 corners disturbance. This incites rapid and positive feedback cyclogenesis (self development), and the upper level height field aloft is augmented by the extreme low level warm air advection (low level warm air advection results in height rises) which develops the ridge ahead of the PV anomaly riding the coast which (splits the northern cortex as others have said). The upper level height rises begins to give the whole storm a negative tilt, which enhances mesoscale jet circulations as well as differential positive vorticity advection which then further enhances warm air advection and increases frontogenesis and the mois baroclinic zone releases more low level diabatic heat to due condensation as air converges etc etc. Hence "positive feedback"/self development process.

A negative tilt system is a development due to this positive feedback system. This is why you always hear mets talking about this. It is important in rapid development and especially nor'easters since they need to rapidly develop to either ride the coastline or take a NW track into the coast.

[stormtracker]

i think the ukie jumps on board for you big time.

Yeah, that does look good. Kinda resembles the 84 hour NAM at this point.

[buckeye]

Yep I agree, UKMET is going to show a serious coastal bomb.

-Nor

not sure why i'm interested, i just find this whole model mayhem interesting even if its between a coastal and OTS. But yea, the Ukie looks like it's going to do what DT was referring would need to happen....vortex splits and a piece falls into the trough. It all boils down to what's going on in the northern stream.

You cant' even really read anyting into how they did on the last storm. The euro had the furthest north solution for most of the run up....the ggem was not quite as north.... the ukie was way south and the gfs was between the ukie and the ggem. The ggem seemed to win in the end. Of course that one was primarily northern stream. In this case it's flipped almost upside down with all the models that were the furthest south with the mw storm are now the furthest nw with this system and the ones that were most north are now OTS....

[Guest someguy]

Snowgoose, the NOGAPS came in much further west than last night. Still not a hit, but significant improvements:

https://www.fnmoc.na...au=132&set=Core

buries eastern va BIG TIME at 120 hrs

[yoda]

The GFS individual ensembles really run the gamut... few out to sea... few monster hits, few just inland

http://www.meteo.psu.edu/ewall/ENSPRS_12z/ensloop.html#picture

[Edge Weather]

There are 4 members there that are just amazing.

The GFS individual ensembles really run the gamut... few out to sea... few monster hits, few just inland

http://www.meteo.psu...op.html#picture

[baroclinic_instability]

The GFS individual ensembles really run the gamut... few out to sea... few monster hits, few just inland

http://www.meteo.psu...op.html#picture

As expected. They have been doing this the last 3 days...mostly supported by a minority of the ensemble members.

[psuhoffman]

Seems to me for the I95 areas that there is little wiggle room in terms of a full phase/coastal hugger with a 'warmer' solution and the flat partial-phased solutions we are seeing. Each successive suite seems to be diminishing that small area of opportunity that lies in the middle for I95 snowstorm. Full phase and the warmer Atlantic air gets drawn in ... a partial phase and this only hits the Southern MA and Eastern New England. Hope we can find that needle in the haystack on future runs, but as noted earlier, there will be wild swings in modeling solutions until data gets into a better sampling area. 12Z tomorrow should start to hone in on things.

you do realize you just described just about every winter weather possability for DC/Baltimore/Philly that is why they all average around 20" of snow and not 50"...

We always need more to go right then wrong and our window is never that wide. Too much amplification too soon and we get an inside storm track and rain. Not enough phasing and the storm is out to sea

There will always be way more misses then hits in a normal winter.

years like last winter are extremely rare

...such is the life of a mid atlantic snow weenie

[Kmlwx]

The GFS individual ensembles really run the gamut... few out to sea... few monster hits, few just inland

http://www.meteo.psu...op.html#picture

Guess it goes to show how small changes can impact the final outcome, and the fact that we are far from determining a final, concrete solution.

[yoda]

GGEM ensembels are on their way out now