#6 Postby AJC3 » Sat Feb 25, 2006 1:48 am
As a quick follow up comment, I'm sitting here looking at a 4-day time lapse from early on the 20th through the morning of the 24th. The static images really don't do this system justice as far as making an analysis goes. So, without the benefit of looking at other data (surface, upper air), and only a foggy memory of some QS images from a few days ago, a few things are apparent to me.
1) Environmental conditions, while allowing the system to form, were never all that great.
Sure, in a relative sense, conditions were quite a bit more favorable than normal (after all, the thing actually spun up). However, I think this speaks volumes about how hostile conditions typically are in the south Atlantic, and how much of an anomaly it was for conditions to remain as favorable as long as they did for the life cycle of Catarina.
Convection pulsed throughout the life of this cyclone but as soon as it did it, shear ripped convection away from the center - initally by northerly shear, then toward the end, the shear became westerly. SST's were marginal, and it didn't appear as if the instability was all that great either - i.e. the air aloft may not have been anamalously cool enough to offset the marginal SST's. I'd need to examine watervapor imagery and sounder-derived upper air temps in that area to be sure, however.
For grins, I pulled out my disc with the January 2004 cyclone imagery, and noted that southerly shear is what did it in.
2) Midget TC = probable QS underestimation of wind speeds
Based on the tight cloud motion I see in the visible time lapse, there's little doubt in my mind that for a time, the sustained winds reached TS force in a small area near the center. I think most people have been ball parking it somewhere between 25kt and 40kt...my guess would be at the upper end of that range...35-40kt. YOMV.
BTW...if anyone has about 100MB of free space, I'd be happy to dump visible and IR time lapses from the 20th through the morning of the 24th. The time lapses are animated gifs (10) files, around 9MB each.[/b]
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