watching ioke make that long run across the pacific as a large typhoon sort of got my hackles up, as after listening to joe bastardi a few years back and observing the time-delayed symmetry of synoptic features in the pacific to atlantic... seeing a storm with a similar type track in our basin gets me a tad worried. right now, what i'll call future florence has a leftward bending track under a large western atlantic ridge, the sort of path that in september tends to generate very large and dangerous hurricanes.
usually these things peak out south of bermuda and weaken as they recurve off or near the east coast. in recent years two hurricanes, floyd and isabel, had similar type tracks. frances might also qualify. these became extremely powerful on their westward run, then began to feel shear and subsidence, screwed up an eyewall cycle and lost power. usually one of these broad hurricanes can do an eyewall cycle or two, then gets permanently gimped with a large ragged eye that never can contract again. the ones that threaten to come in as major hurricanes usually don't keep a well-structured inner core if they go through cycles while recurving above about the tropic of cancer.. so if this is going to be one of those storms to run the east coast, it'll probably show up on our doorstep around september 14 and be a category 2 or so. usually to get a major hurricane to cross the u.s. coast you need it to form relatively close in, intensify at a regular-ish rate, and hit about 4-7 days after developing. longtrackers sometimes hit as majors, but it doesn't seem to happen as often. i'm just talking in generalities, because all we have is a tropical depression with early signs saying it will take on the profile of a classic east coast hurricane.. but many of these find a way to recurve early.
anyhow, long story short, like tip and clark and others... early model runs i'm seeing make me suspect that this will be a large hurricane that will start getting lots of airtime late this week and weekend especially.. and that may threaten the east coast around mid-late the week after.
that wave trailing it has an interesting future in model runs as well. some show the large wake-trough enhanced by the outflow jet of 'florence' as chewing it up. others keep it in an upstream 'sweet-spot' that allows it to develop into a significant storm as well. quite often trailer storms end up shearing out, but there have been some notable storms trailing large hurricanes that eventually break free of the oppression and make their own mark (i.e., frederic and to a lesser degree fran).
man, in a 'normal' season.. it's these F, G, H, I storms that usually are the atlantic longtrackers.
HF 0454z04september