ATL: HERMINE - Models

[Kingarabian]

Track is very close to the Euro. Great agreement on steering at least.

[SunnyThoughts]

http://www.tropicaltidbits.com/analysis ... _us_20.png

[Kingarabian]

So where does this ULL come from? I see no evidence of any ULL in the current sat pics.

In 96 hour frame above the yellow on the NE coast of Florida is the remnants of Fiona.

Trough over the northeast US cuts off and drifts southwest.

Why doesn't the Euro have that trough cutting off?

[RL3AO]

Mark,

Its the trough currently over the Northeast. The GFS has a trough (black line) extending into the SW Atlantic before it cuts off into an upper level low (red circle) and drifts southwest.

[paintplaye]

So where does this ULL come from? I see no evidence of any ULL in the current sat pics.

In 96 hour frame above the yellow on the NE coast of Florida is the remnants of Fiona.

Trough over the northeast US cuts off and drifts southwest.

Why doesn't the Euro have that trough cutting off?

It did and still does to a certain degree but it is slower and weaker than earlier runs.

[tolakram]

120h comparison

[Hammy]

Has the GFS been overdoing the sheer in general this season? I think I remember something similar with Earl as well (and the systems in May/June it didn't even develop until the run or two before they were upgraded.)

[PTrackerLA]

Actually pretty good agreement between the 12z Euro and GFS here, GFS just a bit further south and obviously weaker

[Nimbus]

ULL shown here still causing shear in the GFS run.

http://www.tropicaltidbits.com/analysis ... atl_17.png]

Now that they are forecasting Gaston to be a major it will obviously pump up the ridge that it is embedded in.

The high over the southeastern US might now be positioned a little further west and according to this run the weakness between the two highs provides some shear for 99L.

Of course the weakness might be really squeezed and 99L be a little further south if she is weaker..

[tolakram]

[Kingarabian]

Looks like the 18z GFS begins to deepen it to the southwest of Florida.

[RL3AO]

Has the GFS been overdoing the sheer in general this season? I think I remember something similar with Earl as well (and the systems in May/June it didn't even develop until the run or two before they were upgraded.)

It seems the big difference (at least synoptically) between the GFS and Euro is the mid-latitude trough that moves into the western Atlantic. The GFS digs the trough deeper into the sub-tropics and it cuts off near the Bahamas. The Euro does not. The models have a small but significant difference about 3 days out on how that trough behaves. Small synoptic differences can lead to huge differences in a tropical cyclone.

[PTrackerLA]

With the strong ridging in place at 138hrs I could see this making it pretty far west in the Gulf. The GFS still doesn't seem to be intensifying it much at all in this area whereas the Euro sees excellent conditions.

[tolakram]

[Kingarabian]

Weak TS now 156hrs in the GOM.

[tolakram]

[Nederlander]

http://www.tropicaltidbits.com/analysis ... _us_26.png

GFS ridge slides east briefly before moving back west almost in unison with 99L as it moves across SFL.. If that were to verify, the entire Gulf Coast is in play..

[PTrackerLA]

168hrs, this might be the best 99L can do according to the 18z GFS, . Don't like the direction though.

http://www.tropicaltidbits.com/analysis ... atl_29.png

[tolakram]

Cruising west in the GOM and delayed development. Seems very unlikely.

[Alyono]

MU has it in the Gulf under an upper ridge, yet it somehow does not intensify