18z Model Guidance 12/8

[earthlight]

this is what john is talking about the s/w that deamplifies everything. I circled the areas and compared the two in the 12z and 18z gfs runs. On the 12z gfs you can see how the pieces of energy are most closer together ready to begin phasing....the 18z gfs the pieces of energy are spread out a good bit which deamplifies it, almost like a kicker

Thanks...I created a gif image below that's pretty small but you can see the feature here too. It's over the Ohio Valley at this time frame and this is the time frame that best represents the de-amplification occurring. You can clearly see the differences between the 18z and 12z GFS, where on the 18z run the feature is stronger and further northeast. This acts to de-amplify the height field across the Northeast US and also subsequently slow the phasing process. Also interesting to note how the PV is further south this run. If it was in it's 12z position the surface low would have slid way off the coast.

[LetItSnowInPhilly]

Clearly this is a highly sensitive pattern- the smallest changes can lead to vastly different outcomes.

[earthlight]

Also in the above image notice how the main strong shortwave is slower and further west across AR. All of these things led to the further east solution. Very fragile set up and not as much of a layup forecast as some people though a few days ago.

[tombo82685]

does the ukmet still run out to 72 hrs 6 and 18z? i thought i remember florida state model page having that. I would be curious if it still does to see what its showing.

[Dsnowx53]

The northern stream energy being progressive and thus escaping quicker might make sense given the general progressive flow of La Ninas. This might be a legit development.

[yoda]

does the ukmet still run out to 72 hrs 6 and 18z? i thought i remember florida state model page having that. I would be curious if it still does to see what its showing.

Yes. What do you want of it? I have it

[Kaner587]

The northern stream energy being progressive and thus escaping quicker might make sense given the general progressive flow of La Ninas. This might be a legit development.

I thought the northern stream tends to be stronger in La Nina's ? Or maybe it was in comparison to the southern stream...

[tombo82685]

Yes. What do you want of it? I have it

id like to see how it matches up with the gfs through 72.....

[yoda]

This is 60 hrs on the 18z UKIE

[eduggs]

I'm still perplexed as to where that lead shortwave came from (probably not a good thing). I think it has some to do with the initial clipper which was further south this run as well. The initial energy coming out of the Pacific escaped east towards the Ohio Valley and de-amplified the heights. Also, it's important to note that even around 60-72 hours the energy was slower. These two things combined led to the de-amplification and the trough going negatively tilted later.

I couldn't believe what I was looking at when we still had a positively tilted trough past Arkansas. If that does occur, this thing is not going to wrap up inland.

To be honest I don't really see a distinct new s/w. To me it just looks like vorticity/energy at the base of the trof is slightly less consolidated and slower to get its act together. The exact configuration of the mid/upper level flow is likely to change each run and so too will the surface evolution.

[earthlight]

18z GFS Ensemble spaghetti plots seem to have less inland tracks thus far.

[earthlight]

Through 84 hours the GFS Ensembles are slower and maybe a hair south

[tombo82685]

This is 60 hrs on the 18z UKIE

thank you...it looks like its about the same as 12z at hr 72, the low may be a little further nw

[Dsnowx53]

I thought the northern stream tends to be stronger in La Nina's ? Or maybe it was in comparison to the southern stream...

That's actually a good point, because then you could also argue that the southern stream energy should be faster, too.

Also, it might not even be a timing issue at all. Perhaps since the energy in general is less consolidated, that means the southern stream energy has to slow down, since the northern stream unconsolidated energy then acts as a kicker instead of a tug northward.

Or perhaps it's the other way around.

[earthlight]

102 hours they are colder and southeast of the 12z mean it seems

[tombo82685]

hr 108 ens have a sub 992 low basically where the ukmet has it

[Dsnowx53]

Through 84 hours the GFS Ensembles are slower and maybe a hair south

Slower would most likely be indicative of less consolidated energy.

[earthlight]

It looks like the spread has widened on the 18z ensembles..the surface low is weaker and the precip field is broad. One thing is for sure--they aren't inland. The mean surface low is 992mb off Ocean City, MD at 108 hrs..and then 988 Southeast of Long Island at 120.

[yoda]

hr 108 ens have a sub 992 low basically where the ukmet has it

Is this the mean you and Earthlight are talking about?

[earthlight]

The spaghetti plots look like a kindergarten drawn etch-a-sketch. Not much confidence here.

[tombo82685]

Is this the mean you and Earthlight are talking about?

yes, it shows a low in the position the ukie has at hr 108

[Feb]

Low goes from interior NC to Delmarva to Block Island on the ensemble mean it looks like.

From Will.

[tombo82685]

the 18z ens mean still continues to track the 850 low right over phl or thereabouts

[Sundog]

The individual members will be telling. I'd like to know how many have shifted to a more offshore track.

[Thunder Road]

You shouldn't be -- it's the backside of the storm and a likely colder solution.

yea but when i posted this the GFS was tracking the storm through PIT lol

[earthlight]

Individuals...quite the spread

http://www.meteo.psu.edu/~gadomski/ENSPRSNE_18z/f108.gif

http://www.meteo.psu.edu/~gadomski/ENSPRSNE_18z/f114.gif

http://www.meteo.psu.edu/~gadomski/ENSPRSNE_18z/f120.gif

http://www.meteo.psu.edu/~gadomski/ENSPRSNE_18z/f126.gif

[Kaner587]

Individuals...quite the spread

http://www.meteo.psu...NE_18z/f108.gif

http://www.meteo.psu...NE_18z/f114.gif

http://www.meteo.psu...NE_18z/f120.gif

http://www.meteo.psu...NE_18z/f126.gif

4 inland (but only as far west as central/western NY) 5 Hits and the rest out to sea

[KEITH L.I]

Individuals...quite the spread

http://www.meteo.psu...NE_18z/f108.gif

http://www.meteo.psu...NE_18z/f114.gif

http://www.meteo.psu...NE_18z/f120.gif

http://www.meteo.psu...NE_18z/f126.gif

none of them look like Euro..hard to belive the difference this close in

[Ericjcrash]

Individuals...quite the spread

http://www.meteo.psu...NE_18z/f108.gif

http://www.meteo.psu...NE_18z/f114.gif

http://www.meteo.psu...NE_18z/f120.gif

http://www.meteo.psu...NE_18z/f126.gif

The 2nd to last is 93 superstorm-ish.

[phlwx]

this is what john is talking about the s/w that deamplifies everything. I circled the areas and compared the two in the 12z and 18z gfs runs. On the 12z gfs you can see how the pieces of energy are most closer together ready to begin phasing....the 18z gfs the pieces of energy are spread out a good bit which deamplifies it, almost like a kicker

FWIW the GFS @ 12z was less amplified at 500 and less potent with the mid level vort than the Euro. It also was more progressive with the energy and the movement of the storm, which is why the GFS track is along I-95 for the most part. The northern flow is pushing this along and preventing the dig that the Euro uses to fire up a bigger storm.

I'm not going to get into specific nits about this run of the GFS but I think it's important to note that the GFS was good in '08-'09 at picking up the northern stream features sooner. It may ultimately trend back a bit in the end but I don't think things will be as warm or windswept on the front end...still a rain event but probably a much colder rain and not 60 like the Euro suggests.