STORM2K

Hi, new here – been lurking for several years…I decided to join after one of the posts on the ‘Hilary’ discussion thread reminded me of a question that’s been nagging me for quite some time.
The question is, how good are cloud top temperatures an indication of a storm’s intensity?

I’m aware of course that an accurate estimation of intensity depends on more than just cloud top temperatures (i.e. the storm’s structure, temperature of eye), but how significant are these other factors with respect to the former? I ask because in my limited experience (reading posts on this site and others) most rough estimates are given based primarily on cloud top temperatures.

In the article “HAVE THERE BEEN ANY TYPHOONS STRONGER THAN SUPER TYPHOON TIP?” by Hoarau, et al. typhoons Angela and Gay were estimated to have been more intense than Tip due largely to their colder cloud tops.

But in the 2005 post season analysis NHC estimated Wilma’s intensity to be around 1200Z on 19 Oct. Yet if you watch the IR loops it is pretty evident her cloud tops were coldest at around 0800-1000ish…by 1200 they had warmed slightly (and the CDO had also lost its symmetry). So why was she estimated to have peaked intensity at 1200 (warmer eye perhaps)? Did NHC make a mistake?

Thanks in advance to anyone who can clarify this for me. (PS I’m not sure if this should be posted under this section or the talking tropics section, please move it if it’s in the wrong place.)

Well, I'm certainly not an expert but cloud tops do play a role in determining if a powerful looking storm is a Cat.3/4 or a solid 5. There are other factors like the core temperature or the symmetry of a storm but still a 10 degree cloud temp difference can often be seen as a 10 knot wind speed difference in Dvorak estimates.
For Wilma I think that the top wind speeds occured a little later than imagery suggests as winds tend to lag behind the estimates (that's why the current intensity number does stay the same for awhile even though the satellite raw numbers have already started declining or rising).

If this should be wrong, feel free to correct it.

Yes, that sounds about right, and thanks for the reply.

The CI# is an estimation of both wind speed and pressure correct? So does central pressure lag behind the satellite data as well?

Teddyfred wrote:Yes, that sounds about right, and thanks for the reply.

The CI# is an estimation of both wind speed and pressure correct? So does central pressure lag behind the satellite data as well?

No, not that I'm aware of.

Teddyfred wrote:But in the 2005 post season analysis NHC estimated Wilma’s intensity to be around 1200Z on 19 Oct. Yet if you watch the IR loops it is pretty evident her cloud tops were coldest at around 0800-1000ish…by 1200 they had warmed slightly (and the CDO had also lost its symmetry). So why was she estimated to have peaked intensity at 1200 (warmer eye perhaps)? Did NHC make a mistake?

I've seen that countless times but no one seems to ever talk about it. I don't know if there is any scientific explanation or acknowledgment of TC's developing quickly with cold cloud tops that then have warming cloud tops right when it's organization has improved (either by a lot or just some). There might be some process that happens within the internal structure to create this effect. Just curious, where do you watch these Wilma IR loops from?

Cyclenall wrote:

Teddyfred wrote:So does central pressure lag behind the satellite data as well?

No, not that I'm aware of.

Does this mean that in a TC that weakens quickly, by the time highest wind speeds are reached, central pressure is already on the rise?

Cyclenall wrote:Just curious, where do you watch these Wilma IR loops from?

There are several on the internet; one of the best can be found here:
http://cimss.ssec.wisc.edu/goes/blog/wp ... 4_anim.gif