Margie
(Senior Storm Chaser)
Thu Oct 20 2005 03:10 AM
Re: Wilma a Category 4 Hurricane Moving West Northwest

Quote:

Is the fact that we have had three cat 5's in one season a record also? I haven't confirmed that yet.



Yes. Wilma has set or tied a lot of records in addition to that one: first "W" storm, tied 1933 record for number of storms for a season, tied 1995 for number of major hurricanes, fastest intensification for both pressure and winds, lowest pressure ever measured in ATL basin.

Evening everybody.

Waves at buoy 42056 have started to go over 20 feet now. This will be interesting to watch over the next 36 hours. I'm not sure how long it will report back once Wilma gets close, passing west of the buoy. If Wilma deviates to the east of the projected track (not likely) things would be immensely more interesting, as she'd intensify and the eye would go fairly near.

Oddly, Wilma is looking remarkably healthy and well-organized for being in an ERC. She maintains a continuity especially in the strong core, and continues the same rhythm of increasing/decreasing convection and size, and continues to maintain a uniform "buzzsaw" shape. The eye still maintains a very distinct appearance even while filling in. In an odd way she still seems to be very steady state. She does look to have dropped down to a Cat 4 now, but likely to still be maintaining a very low pressure.

Maybe it is just that the eyewall replacement is happening very very slowly (Wilma has taken her time with just about everything).

There have been a lot of comments about wobbling, changes in direction, but Wilma is moving very consistently. Her movement is oscillating in a way that is described as cycloidal. Does anyone remember the drawing toy Spirograph? A lot of the patterns were all generated by cycloidal movement. To see this type of movement, ake a pencil and cut out a circle from cardboard, punch a hole in it that is off-center. Now cut a curve into the remaining piece, and lay it on a piece of paper, stick the pencil in the hole of the circle, and then rotate (not slide) the circle along the curve. The movement the pencil traces out onto the paper is cycloidal. The movement of the moon about the sun is similar.

So...all intense hurricanes have these movements, however sometimes they are very small and not perceptible. With Wilma the movement is quite large, making it noticeable on satellite images, but it is not particularly unusual. The technical term that was mentioned in one of the discussions is "trochoidal oscillations" and so if you are interested in finding out about why more intense hurricanes are prone to this type of movement, goggle it with the word hurricane.



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