A few changes with Bertha - FLHurricane.com

The 11am advisory still has a 300degree motion associated with Bertha.

It appears irregular convective prominences are causing "wobbling" of the track. These wobbles can often take as much as 3 or 4 hours to unfold. It is perhaps too easy in those intervals of time to believe something unexpected is taking place. But, I am not seeing a big enough deviation between her apparent axis of circulation to that of the clear NW track motion provided by the TPC - they seem to be aligning just fine. Moreover, there isn't really much compelling synoptic reason that asserts Bertha should be resuming a west motion, for the time being. Steering field remains weak, but with a trough "denting" the Bermuda ridge as it presses off-shore the NE U.S. over the next day and half, if anything this offers at least a small argument for continue northwest or perhaps even eventually a north motion...albeit slowly. Speed of motion does not appear to have any means to really accelerate until perhaps very late in the 5-day forecast period.

What I am seeing in recent guidance is a clear emerged consensus that the next trough (4+days) will be a bit more substantial. The Euro model, for example, uses that trough to pick up Bertha and deliver her to the graveyard. Other models including the UKMET (also, 00z run), run Bertha up the eastern flanks of the baroclinic wall associated with the same trough. The Canadian model is the slowest with this overall evolution but still argues for the same sort of thing...stronger trough nearing D5 sets up a baroclinic axis off-shore and this veers the steering field more discernibly toward the graveyard and an alas re-curve scenario finally takes place there after.

It is possible that after this first trough (D1-D3) leaves the NW Atlantic, the ridge may respond a bit more robustly than currently modeled. If that were the case, than said deeper trough D4-6 may find an axis more west of currently depicted. That offers some envelope of discussion for gaining more longitude - perhaps - than currently suggested. There has been a seasonal bias in the models to try and dampen the west-central Atlantic ridge too much. Just something to keep and eye out for, as this would offer a greater degree of threat to Bermuda.

By and large, the greater synoptic challenge to preventing Bertha from re-curving has been answered for in my mind. Over the next week and beyond, it seems troughs passing from the GL-NE U.S. at higher/middle latitudes will pretty much seal a fate that will ultimately force Bertha seaward. Simply a matter of when. It is probably...actually...that what we are seeing is a step-wise escape to higher latitudes. First a weakness in the ridge instantiated a NW motion over the last day.5; that weakness fills and Bertha slows down and wobbles; then another weakness associated with a trough passing NW of Bermuda over the next two days may focus more NW motion; she slows again as said trough leaves the area; then we await a deeper trough expression in the extended to put the final hammer head down of that coffin nail. This seems the most likely pattern of behavior for Bertha's future to me.

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