Tropical Storm Florence

September 5, 2006

The big picture for Tropical Storm Florence remains similar to how I outlined it on Sunday. The storm is currently in less than favorable conditions, but that is expected to change in the storm’s favor in the future. It remains in a position that could threaten the US, but it will be the position of the Bermuda high that determines whether Florence affects land.

On Sunday I stated that guidance was indicating a hurricane in two to four days and opted for the latter part of the spectrum, which implied a hurricane by Thursday afternoon. It now appears that estimate was a bit too soon. One reason being that a shear generating trough to the north of the storm had been forecast by models to simply lift out. Instead the trough fractured, which leaves an upper level low near the path of Florence. That low should impede Florence’s intensification to a hurricane until Saturday, in my opinion. The Hurricane Center’s forecast brings Florence up to hurricane strength by Friday, which is slightly slower than what model guidance suggests.

Another obstacle for Florence was a disturbance to the southwest of it, which before the birth of Florence was being monitored for signs of development. The disturbance did not develop, but it did interefere with the circulation of the developing tropical storm. That obstacle is now out of the way as Florence’s circulation has subsumed the disturbance. The result though, is another hindrance for Florence; the lack of a compact circulation is another reason for intensification to be in check during the next couple of days.

One more potential wrench for Florence’s intensification prospects is a disturbance to her east. Dr Masters devotes a paragraph of his discussion. The interaction he describes is not necessarily a given. Earlier this season, in the eastern Pacific, hurricanes Bud and Carlota developed about 700 nautical miles away from each other without Fujiwhara interaction, and without the lead storm (Bud) being affected. As such, I don’t think Florence will be affected by the disturbance if the current distance between the two (about 800 nautical miles) is not narrowed substantially.

As far as the path of Florence goes, the near to mid term forecast is unchanged, with a west-northwest/northwest course persisting. At the latter end of the forecast period, most models turn Florence to the north in response to the Bermuda High being shifted to the east, thereby opening up an alley for Florence to turn out to sea without affecting the United States (though if such a turn were to occur as quickly as the GFDL model is forecasting, it could affect Bermuda).

As my climatology post below shows, that is the most likely scenario, however the possibility of the Bermuda High being more resurgent than forecast or the development of a blocking high over the Canadian maritimes and thereby forcing Florence into North Carolina or the northeastern states remains plausible. We still have plenty of time to watch the situation unfold before having to be concerned with that prospect.

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