Hurricane Warnings up from Grand Isle, LA to Apalachicola, FL and Puerto Rico

First, let's look at Jeanne (Ivan in the next post). I've been eating crow here at FSU with this one -- I didn't figure this would have a shot, but it's defied my predictions. That said, it's got some landmasses in its way, including the Dominican. It is looking rather well organized tonight and might become a hurricane in the next day or so if it can miss Puerto Rico and the Dominican.

Track -- unless a trough well to the north of Bermuda continues to dive, it won't pick up Jeanne. All it may do is weaken the steering currents a bit, but that's not even a given. In the short term, Jeanne should continue moving just north of due west around the subtropical ridge. On this course, it might just nick the SW tip of Puerto Rico (thanks ShaggyDude!) and will likely pass over the island of Hispaniola, if only on the north side.

The ultimate track will be the key to the storm's survival, as though I don't see shear increasing too much, the favorable upper-level diffluence will likely weaken just a tad and the wind field with the system is small and tight. If it gets disrupted by the mountains of Hispaniola, it might sound a death knell for this storm -- or at least substantially weaken it -- which isn't necessarily a bad thing.

Afterward, the storm should continue moving in a general WNW fashion to the central Bahamas in about 4-5 days, where it should be near the end of the subtropical ridge. Problem is, there really won't be a trough to pick it up. Ivan looks to stall out over the central Applachians and create sort of a blocking effect -- a Rex block -- where it sits below a high and disrupts the overall steering flow. Troughs can lift up and around the block, but Jeanne will be too far south in all likelihood to feel these effects. A slow, gradual WNW movement beyond 4-5 days can be expected, not unlike Frances.

The saving grace for Florida might be Ivan, as ultimately it should begin to move out to sea in 6-7 days. The trough it leaves behind in its wake as it transitions into an extratropical system (assuming, of course, it doesn't completely die out over the mountains) might be enough to swing and pick up Jeanne, sending it to the north. With the slow forward motion expected at that time, it could be enough to spare the entire United States. However, it is way too early to make that call and right now, at 6/7 days out, it's 50/50 for either scenario. People from Cape Hatteras south to Key West need to watch this one.

Intensity should be held somewhat in check by the small wind field interacting with Puerto Rico, Hispaniola, and the Bahamas, though the storm should reach hurricane intensity in the next day or so before then. It will have a chance at regaining some strength after leaving Hispaniola, but as it moves further into the Bahamas, cold upwelling from Frances combined with shallow waters (not as much energy) should keep intensification in check.

As an aside, the storms we have had near shore this year should help to keep anything else on the horizon from affecting the mainland with as much force just due to coastal upwelling of shallow waters, at least in the next few weeks. I don't want to sound the bell for the season after Ivan and Jeanne for the U.S., but the peak is behind us and there is only so many storms that the basin can handle in the same location. The chances after these storms of a significant U.S. impact dwindle pretty greatly -- but do *not* go away -- once they get out of the way. That doesn't diminish in any way what they have done, however.

1 day position: along the southern coast of Puerto Rico near 18.5°N and 66-66.5°W, 65-70kt hurricane
3 day position: just north of Hispaniola near 20°N 71°W 50-55kt tropical storm
5 day position: central Bahamas near 23°N 75°W 60kt tropical storm.
This isn't too far off of the NHC position and intensity, except a bit further south and a tad slower at days 4 and 5 and weaker due to interaction with landmasses.

Ivan coming up...

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Edited by Clark (Wed Sep 15 2004 01:24 AM)

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