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Thursday, September 09, 2004 |
| At 5:00 PM EDT, Ivan was 350 miles southeast of Kingston Jamaica and moving west-northwest at 15 mph. Maximum sustained winds are down to 150 mph and pressure is 921 millibars (27.20") This makes Ivan a strong category four hurricane It seems that the weakening is due to eyewall dyanmics. It is anticipated that Ivan will fluctuate between category four and five before it starts hitting land. The forecast track has shifted back to the left (west) after drifting to the right over the past three advisories. While the shift in the forecastback to the west is unwelcome to most (from the standpoint of not wanting another hurricane to hit Florida), I am glad to see it from the standpoint of accurate forecasting. I was not thrilled with the 'split the difference in the models' approach that seemed to typify the 11 PM forecast last night and those that followed it. The grad students who were in the computer lab prior to my Atmospheric Dynamics class were pretty derisive of it as well. As the discussion states, most models are in general agreement for the first three days of the forecast period. Almost all of them have Ivan hitting Cuba in the vicinity of the Bay of Pigs. (There is some dissension on that however... the Superensemble continues to be to the west of most models and has Ivan coming across Cuba at its narrowest point, just west of Havana. The UKMET model is even further west). The divergence occurs after the three day mark with the Florida peninsula being the center of a fairly wide spread. The GFS model continues to insist upon hooking Ivan to the northeast (although it seems to bring him closer and closer to the east coast of Florida on each run). At the opposite end, the UKMET model has only a gradual turn to the north and northeast that has Ivan hitting the panhandle. The superensemble moves Ivan a fair bit slower and has it roughly 100 miles west of the Fort Myers area at the end of its forecast period on a north-northwest track. The National Hurricane Center forecast seems to mirror the track offered by the NOGAPS model, which while it is similar to that of the superensemble is wildly different in timing. It seems that the NHC has taken the NOGAPS track with the superensemble's timing. For each wobble to the north that Ivan makes that would seem to have it miss Jamaica, Ivan has offered an offsetting wobble to the west that puts it in the bullseye again. As I said earlier, things look bleak for the island. The decrease in forward motion of Ivan offers a bit more planning time. The timetable for decision day may have slipped back one to Saturday. As noted elsewhere, though, the Florida Keys have started to evacuate. That's because it was aptly demonstrated in 1992 how difficult of a place it is to evacuate in a timely fashion. US 1 is two lanes for nearly the whole stretch, which greatly impedes the flow of traffic. As a result, the Keys get evacuated well ahead of time whenever there is a hurricane in the general vicinity. Finally, it seems that I ended up downslope from an Instalanche. Lots of visitors today. Had I known they were coming, I might have offered something more insightful. Kudos to Brendan and also to Alan Sullivan who has also been following Ivan with the benefit of knowledge of the Carribean countries affected . Very good reading. Weather comment []5:16:41 PM  trackback []
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| At 11 AM EDT, Hurricane Ivan was 455 miles of southeast Jamaica moving to the west-northwest at 15 mph. Winds remain 160 mph and minimum central pressure is 920 millibars (a drop from my last upate, but 1 millibar higher than the lowest pressure observation from this morning). The extended forecast remains uncertain and as I've discussed previously, it all depends on the strength of the high pressure ridge. If it remains strong, the hurricane will proceed into the Gulf off the western coast of Florida. If the ridge weakens (and splits) then the strom will go east of Florida. Still too soon to tell which scenario will play out. Something I should have mentioned last night (that others have noted) is that category five storms do not hold that strength for an extended period of time (because they require essentially perfect conditions to exist). To see this point, it is useful to look at a couple of recent category five storms. Last year, Isabel made category five status in the Atlantic and held it for 27 hours before dropping to category four to six hours, bouncin back to cat five for nine hours and then weakening again, eventually going down to a category two storm before making landfall in North Carolina. In 1998, Mitch was the strongest October hurricane in recorded history. A 52 millibar drop in pressure over 24 hours preceded his making category five. Mitch held category five status for 33 hours before weakening to a category four prior to his landfall in Honduras. It is worth noting that Ivan's pressure is the lowest recorded in an Atlantic basin hurricane since Mitch (who bottomed out at 905 millibars) . Weather comment []11:33:09 AM trackback []
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| The most recent pass of the Hurricane Hunter through Ivan found winds of 160 mph. Minimum central pressure is 925 millibars. Those numbers make it a solid category five hurricane. An absolutely incredible bit of intensification the storm underwent in the past twelve hours. And quite scary. Weather comment []1:58:11 AM trackback []
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© Copyright
2004
Charles Fenwick
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Last update: 10/2/2004; 11:03:33 PM .
Last update: 10/2/2004; 11:03:33 PM .
