Not understanding north turn - ensembles

[x-y-no]

In the absence of a strong east-coast trough (like what happened with Floyd) I'm not understanding why the models (particularly the GFS) are taking this north rather than wnw or nw across Florida.

Looking at the GFS ensembles from this morning:



Ridge looks strong Thursday.

----



A little weaker but still sticking well into the Gulf, and with the trough digging in the west.

----



Getting thinner now, but still reaching into the Gulf. Also, why should it be getting thinner with the trough still digging in the west? Shouldn't that pump the ridge a bit more?

----



Finally backing off Saturday night/Sunday morning - but by then the official track has Frances nearing Jacksonville.

---

It looks to me like this is more conducive to a south/central Florida landfall, then tracking up to the Florida panhandle.

What am I missing?

[Air Force Met]

The high to the north of Frances is pretty strong now. But...as it moves around the western side of it...it is a lot weaker. There is a trough that will erode it enough to allow for a turn more to the NW. Notice on your images how the high juts out west of the storm like a banana. It is moving around a part of the high that is not strong enough to keep it south. So...its really the high being weak in that area more than it is some monster trough taking the high out all together. Tropical cycles can move into areas of weak ridging.

[hial2]

There is a trough that will erode it enough to allow for a turn more to the NW.

Can you tell where it's at, or is the through mentioned just a forecast? thanks

[PurdueWx80]

12Z Eta at 300 mb Friday evening:



The trough in the west just isn't far enough east to force her to a hard northerly turn. Last night's 00Z GFS ensembles were evenly split between 3 places: NC, northern FL, and Central FL to Gulf. The 00Z GEM ensembles leaned much more towards the Gulf option, but there still some members to the right, although they turned her due north from where she is now. That's not an option. That is one monster full latitude trough though, and with that strong jet streak to the west (120-130 kt perhaps), this thing will dig even more. I really see this as the best option, and that means the ridge would amplify enough to keep her on a WNW to NW path as long as possible. I honestly think this is a central FL to northeast Gulf storm. From there, this looks like one hell of a nasty storm all the way through the Appalachians or eastern Great Lakes (give or take 200 miles), as her energy combines with the incoming trough. If Frances weren't there, that trough would cause a severe weather outbreak to beat the band.

[x-y-no]

There is a trough that will erode it enough to allow for a turn more to the NW.

Can you tell where it's at, or is the through mentioned just a forecast? thanks

I assume he means the trough over the Canadian maritimes in the 24, 48 and 72 hour plots above. That's lifting out gradually after tomorrow, though, and at the same time the trough in the west is digging in (which outh to indicate a stronger atlantic ridge if I'm understanding things) so I'm not sure why the ridge continues to weaken so much after 24-48 hours.

AFM is the pro, though and I'm just learning this stuff, so I'd trust him before I trust me.

[PurdueWx80]

12Z GEM and GFS going for a FL/GA border hit. That's a one in a million year storm.