Question for the Pros re: SSTs

[al79philly]

Hi - I have a quick question. If you look at this map http://grads.iges.org/pix/atlpot.gif the map indicates that the SSTs in the area in which Ivan has been located for the last day would only support a Cat 4. However, Ivan has clearly been a Cat 5 for a good deal of that time.

I was under the assumption that these waters COULD NOT support a Cat 5. Is it safe to say that this map only serves as a guideline and not a "hard and fast" rule or am I missing something?

[btangy]

These maps do serve as a guideline. Under no shear conditions, I find these maps quite useful. Ivan has been pretty much right around its maximum potential intensity in the Caribbean, though has probably peaked a little above it for short periods of time.

[HurricaneQueen]

Al:

It's been a CAT 4 for the last two advisories (155 mph) so maybe the map is correct. of course, there would be other factors for the reductions but I'm not well enough versed to address them.

[Hurrilurker]

Hmm. According to that, I'm not sure why the NHC keeps insisting on lower SSTs that will weaken Ivan in the Gulf. Looks like a good portion of the area they have it traveling though supports Cat-5, and in addition that pool of cooler water left in Frances' wake, around the Panhandle corner, seems to be receding (warming up) as well. What gives?

[wxman57]

SSTs are only one factor that can influence intensity. Low vertical wind shear is probably more significant. Other environmental variables are very favorable for a high intensity hurricane, even though SSTs may appear to be marginal for Cat 5.