Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
Reged: Sun
Posts: 2565
Loc: Melbourne, FL
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Tonight the Dynamic Duo isn't looking too dynamic. I don't see anything to worry too much about yet - with either storm. Isidore doesn't have a lot going for it. The upper level low is displaced over 100 miles to the east southeast of the surface circulation. The outer bands are still impressive - and very tropical - but the surface center is barely alive. I believe that Isidore has become a subtropical hybrid system - a very impressive one in terms of size, but its no longer tropical. Even calling it a subtropical storm would seem to be generous, and yet it is an amazing meteorological entity. We had some true tropical downpours here in Melbourne this evening - from a system that is centered over 675 miles away. Isidore would indeed be a remarkable case study for a student of meteorology - the expanse of its circulation is just unreal. It is certainly the largest minimal tropical storm that I've ever seen. Dr Lyons (TWC) made a keen observation earlier this evening, i.e., regeneration was not likely because this huge system no longer had an upper level anticyclone over or near the center - and he was correct. Without anything to enhance outflow near the center, core redevelopment doesn't have a chance. The overall inner low pressure area has expanded greatly as the cyclone filled from 934mb to 987mb. Isidore will yield some heavy rains along the northern and eastern Gulf coasts, but any winds of significance will probably be very localized. I'd expect a bigger problem from high surf rather than high winds. The surface low may expand into such a broad area that even determining a landfall point may become more of an exercise in central geography rather than actual conditions. Isidore was, and still is, a storm that will be examined for many years.
Lili is also an interesting cyclone. She has been under southerly shear for most of the day (still is) - most of it from an upper low to her southwest. As a result, her upper level circulation is displaced well to the north of the surface center. This probably accounts for the disparity between the high surface pressure and the strong winds in her northeast quadrant. Yet even with moderate shear, the system is still strong and she's developing a fairly large circulation envelope of her own. Forward speed has slowed considerably. TS Kyle has really reinforced the ridge between them - more than I expected - so I'd still expect an eventual track to the west northwest and then northwest. As Isidore pulls off well to the northeast (on the continent, not the Gulf), he will trail a pretty good trough which should eventually capture Lili and pull her north, and finally northeast. The timing of that turn will determine who is in trouble and who is safe. Opposing viewpoints (or even agreements) are solicited.
Cheers,
ED
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HanKFranK
User
Reged: Mon
Posts: 1841
Loc: Graniteville, SC
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got an opposing viewpoint for ya, yeah. lili doesnt recurve. going to miss the digging behind isidore, that pulls out, big surface high blocks the escape to the north... and the semi-permanent ridge builds back. think this will be around florida early next week. that's if it survives. it has a history of having the low level center go racing ahead, weaken.. then a new center closes off at the southwest end of the main convective mass and repeats the process. looks to be happening again today.
kyle, if it doesnt get sheared to death, is more or less caught in the open atlantic.. may keep working its way westward under ridge pulses with time.. as i have yet to see a convincing model depiction of it escaping the ridging. when its track is done, think it may analog to ginny 1963, inga 1969... or some odd autumn central atlantic storm of the like that couldnt seem to catch a decent amplification and go with it.
share your thoughts on isidore. another contributor to the impression that hurricanes are a lot of hype that never come through any more.
ed, african wave train seems to have stopped. think we'll get any more storms this fall?
HF 1750z25september
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