The trough is still too far off to have an effect. It also looks to me like the ridge may at present be pushing a bit harder than expected. Ie., maybe 50-100 miles additional “push”? But, both the “cone” and many models allowed for such. (Any one model “track” should be interpreted as, just to make up some numbers, “10% chance the center will be at “xy” location on the track at time “t”, 90% chance it will be somewhere else, but less than 10% chance at any other particular location than “xy” at “t”.)
(My apologies to any “real” meteorologists reading that crude explanation with fabricated numbers! Maybe one can explain it better...)
The question is, what shape will Irma be in when she (likely) makes the turn?
the point is, the trough can start breaking down the high currently steering the system well before it gets close to Irma.
Two things in play. Arrival time of trough influence. And position of irma when that occurs. At present, that will have to be at, least as south as Cuba. So the storm will have to transverse Cuban influence for awhile. She is already tracking at the southern outlier if not below that. So hardly anyone ran the influence numbers at this range. And she just hit Cat 5 before slamming into Cuba.