Looks like a cat 3 now on the sat imagery

Derek Ortt · #1 Postby **Derek Ortt** » Sat Sep 13, 2003 6:36 pm

No doubt about it, Isabel is no longer a cat 5 hurricane. Cloud tops look to have warmed by about 20 degrees C and the eye has expanded. This satellite signature is typical of lower end cat 3 hurricanes. However, Isabel is still probably a cat 4 due to the spin down time and the sat signature has always looked its worst at this time, which happens to be the diurnal minimum

mf_dolphin · #2 Postby **mf_dolphin** » Sat Sep 13, 2003 6:42 pm

According to my plots on Fabian, Isabel is crossing the path left by him at this time. Maybe that's a contributing factor as well. :-)

#3 Postby **cycloneye** » Sat Sep 13, 2003 6:44 pm

Yes that is the area where Fabian was and there are some cooler spots left.

Derek Ortt · #4 Postby **Derek Ortt** » Sat Sep 13, 2003 6:44 pm

That very well may be the case. If so, expect Isabel to quickly regain its lost intensity tomorrow

#5 Postby **Air Force Met** » Sat Sep 13, 2003 6:45 pm

IT has some high HHPs to go over tomorrow. IF the eye can tighten up some....it ought to be interesting.

Thunder44 · #6 Postby **Thunder44** » Sat Sep 13, 2003 6:51 pm

It may be nothing significant. This afternoon it didn't have so much deep convection around the eye yet, it was stronger then it was this morning with deeper convection. I think eyewall dynamics are playing a roll again, like the NHC expects to happen, just fluctions in intensity. The NHC says it was moving into warmer water too.

calidoug · #7 Postby **calidoug** » Sat Sep 13, 2003 6:54 pm

Per the earlier post on the subject:

Isabel is a very rare Annular Hurricane.

The large eye, in this case, does not indicate weakness.

Remember the whirling vortices of death (tm) within it. It's a somewhat different beast than the normal cyclone structure.

As such, it doesn't lose intensity nearly so fast, and slightly warmer than expected cloud tops can be misleading.

Check out the PDF that was posted. Very interesting.

#8 Postby **Steve Cosby** » Sat Sep 13, 2003 6:55 pm

Do keep in mind the "annular hurricane" theories and lets see if they hold.

I believe the article Derecho posted stated that this class of hurricane will not reduce intensity very quickly. So, we may not see it actually fall to the Cat 3 level before hitting the high heat areas again.

For completeness, here's the link to the annular hurricane article again:

http://www.ssec.wisc.edu/~kossin/articles/annularhurr.pdf

#9 Postby **Steve Cosby** » Sat Sep 13, 2003 6:55 pm

Well, Calidoug beat me to it but here is the link properly posted:

http://www.ssec.wisc.edu/~kossin/articles/annularhurr.pdf

Derek Ortt · #10 Postby **Derek Ortt** » Sat Sep 13, 2003 6:57 pm

For the record, I am estimating this to be a 120KT hurricane. As I stated before, ther eis lag time between the sat signature and the wind speeds. (Consider this a rare time when I publicly state my sat estimates. Normally, they are just written in an e-mail or on a piece of paper and given to who ever is doing our forecast)

#11 Postby **Steve Cosby** » Sat Sep 13, 2003 7:01 pm

Am I reading things right: there is no recon on its way at this time? Next takeoff is not until 10:45 tonight?

That's a shame, I would love to know if Derek is right given the annular theories.

Looks like a cat 3 now on the sat imagery

Looks like a cat 3 now on the sat imagery

Annular Hurricane

Wrong tags

Recon

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