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East Coast Threat/Sandy Part III


free_man

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The more I look at how the Euro "does it" and how the GFS sends it out to sea... it seems to me it has a lot more to do with downstream ridging than upstream shortwave/trough.

The Euro kept showing a ridiculous phase despite often changing the orientation of the shortwave and trough because its insane blocking made a phase inevitable. It builds the really strong ridging in between Sandy and the North Atlantic low, but the GFS does not, which allows Sandy to find a weakness.

The trough on the GFS was stronger this run but that won't make a difference if Sandy somehow finds a weakness.

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The Euro kept showing a ridiculous phase despite often changing the orientation of the shortwave and trough because its insane blocking made a phase inevitable. It builds the really strong ridging in between Sandy and the North Atlantic low, but the GFS does not, which allows Sandy to find a weakness.

The trough on the GFS was stronger this run but that won't make a difference if Sandy somehow finds a weakness.

Exactly. It will find the weakness. It will only phase if it doesn't have a chance to do anything else lol.

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The Euro immediately wants to go omega block with ridging staying strong on backside of big N Atl low and forcing Sandy to cut off.

This is the issue. The GFS is actually a little more energetic with the Central US trough, which speaks to this point even more. In the graphic below with the GFS and Euro side by side, you can see instantly that the GFS does not want to build the ridge between the North Atlantic ULL and the TC in the Southwest Atlantic. However -- this run was a big step in the right direction in that regard, but just not enough. Should the GFS be correct with this idea -- Sandy would have an escape route to the north and east at least for a time.

It's worth noting that the Euro also builds in the Newfoundland blocking/enormous positive anomaly faster as well.

post-6-0-69169700-1351138677_thumb.png

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To put it into further perspective -- the strength of that ridge between Sandy and the North Atlantic low is very important as well. With that ridge there, the TC has no escape route so it literally meanders around until the Central US trough captures it. The 12z Euro was far more anomalous with that ridge than last nights 00z run, so the system slowed down and was captured at a lower latitude.

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This is the issue. The GFS is actually a little more energetic with the Central US trough, which speaks to this point even more. In the graphic below with the GFS and Euro side by side, you can see instantly that the GFS does not want to build the ridge between the North Atlantic ULL and the TC in the Southwest Atlantic. However -- this run was a big step in the right direction in that regard, but just not enough. Should the GFS be correct with this idea -- Sandy would have an escape route to the north and east at least for a time.

It's worth noting that the Euro also builds in the Newfoundland blocking/enormous positive anomaly faster as well.

post-6-0-69169700-1351138677_thumb.png

Yeah if you loop an Atlantic 500mb heights/vorticity on the Euro and GFS it's amazing the difference in what you get with orientation and type of blocking.

You're right too that the 00z didn't get worse than the 18z run. So the downstream ridging looks a bit better... just nothing like the Euro.

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FWIW, 00z NOGAPS pummels ACY... and I mean pummels... upper 940s/low 950 mbs at 96... very close to 00z/12z EURO but prob worse... 968 mb at 108 in SC PA/N MD

Yeah... impressive. Schwartz Synoptic Seven?

To put it into further perspective -- the strength of that ridge between Sandy and the North Atlantic low is very important as well. With that ridge there, the TC has no escape route so it literally meanders around until the Central US trough captures it. The 12z Euro was far more anomalous with that ridge than last nights 00z run, so the system slowed down and was captured at a lower latitude.

That's the whole ball game. If that ridging noses down and starts the process of going from Rex to Omega earlier then we're in business. If not... weakness gives Sandy the escape hatch.

gfs = good for sandbag

Good for Sultan too!

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Yeah, you can see that the 00z GFS actually improved with respect to its blocking compared to the 12z run. But since it wasn't as strong as the Euro was, it still found a weakness.

The 00z GFS at 81 hours is shown below. Look at the 570 dam contour really trying to wedge between Sandy and the North Atlantic ULL.

gfs_namer_081_500_vort_ht.gif

Now look at the 12z GFS at 93 hours. It does no such thing...the 570 dam contour is not wedging at all. As long as the trend for the "wedging" continues, the GFS will eventually cave, and consistently so. The 12z GFS could have easily escaped, but for some reason it just didn't place the same emphasis on the weakness.

gfs_namer_093_500_vort_ht.gif

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Even if there is a slight weakness how guaranteed is it for Sandy to actually utilize that weakness and slip off to the NE?

Depends on how deep Sandy is and how she "feels"it ... As of now, if that weakness is there, she'll slip out and do that big question mark pattern until she comes back into NS or ME (ie. 0z/12z GFS). If that ridge builds in, we have a Euro/NOGAPS solution.

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