1992 Andrew report update

[Tampa Bay Hurricane]

Elena looks to have been quite difficult to predict

[Ivanhater]

interesting stuff, i think this just goes to show us, as Derek has stated many times, that a cat 3 can do terrible damage once thought not possible...

[Derek Ortt]

one other thing bout Andrew

The cat 3 winds were primarily located over the sparsely populated marshland. The populated regions only received cat 1 and 2 winds... yet, there was still more than a billion in damage in 1992 dollars

[WaitingForSiren]

I dont really get all this talk about only Cat 3 storms making landfall in the GOM when Camille was a cat 5. Katrina was a Cat 4, possibly even a 5, wasnt she?

I think as the dynamics change and the water heat content changes, along with eyewall cycles each year it will be varied. There is no such thing as a spot where the hurricane will always weaken, unless of course there is cold water there.

[Scorpion]

Katrina was a 3, and it is unknown whether Camille was a 5.

[Derek Ortt]

katrina was a 3, and the NHC even said that the data didn't even justify the winds that the assigned to it in BT

I'll bet the farm that the reanalysis finds that Camielle was a 3 or a 4

[LSU2001]

Derek,
While I agree with your analysis of downgrading storms such as camile and Katrina, I disagree about the waters just offshore being cold or cool just below the surface. I have scuba dived offshore of La for years and in the summer and in the heart of hurricane season the water is bathtub warm down to at least 100 ft. I guess I will have to bring down a thermometer on my next trip to really find out what the temp below the surface is. Now I realize that I am talking only about 45-50 miles offshore but I find it hard to believe that the gulf cools off that much further out.
Tim

[Derek Ortt]

I believe that the waters are churned up more than 100 feet. I believe that the first 200 feet is what really matters

Now, in the Caribbean, the 26 degree isotherm is several hundred meters below the surface. The cold waters are never upwelled there, even if a slow poke like Wilma or Mitch sits in the same place for days. They never ran into upwelling issues

[LSU2001]

Thanks for the clarification. I can see the upwelling causing rapid cooling of the water. I also believe that an influx of dry air from texas and southwest US cause a lot of the weakening that we see in these storms. If you look at the radar loop of Katrina you will see the dry air enter the south west part of the storm and that part of the eyewall seems to simply collapse. It later partially reforms but the weakening is quite evident.
Tim

[Pearl River]

I don't know how they can go back and change Camille since the last hurricane hunter before landfall had mechanical problems. The last pressure measured was 26.62 and winds earlier in the day were measured at 160mph.

[Derek Ortt]

we can do extraps based upon the pressure rise befor elandfall. What has bene observed is that the maximum winds start to decrease, before the winds start to decrease. This happened in Dennis and Ivan

[WaitingForSiren]

Katrina was only a three? No way, it had barometric pressure of cat 5 storm and judging by the damage theres NO WAY that thing was a three. Im pretty sure the small section of southern Lousiana it side-swiped counted as a landfall, didnt it?

And i highly doubt Camille was a 3, are you nuts?

[MGC]

Since the NHC don't have the tools to look back at Camille, how are they (NHC) going to reanalyse Camille? They don't have GPS sondes, no SFMR, no doppler radar. Nothing but hours old recon report and 909mb pressure observed at landfall. Since the pressure was up only a few mb there is evidence that Camile didn't have a eyewall replacement like Katrina did. The GOM was quite warm since 1969 was a very hot year along the gulf coast. That lead to very warm SST and Camille passed over the loop current so she had plenty of warm water. She had a small eye on the order of 8NM in diameter. Do the math, 909mb and 8NM eye. What does your formula crank out? Just curious......MGC

[Derek Ortt]

I need the total size of the storm, and the pressure in the eye wall before I can do any calculation

what we can do is look at the old recon data and apply the correct reduction factor

[Derek Ortt]

yes, Katrina was a 3. The NHC put a line in the report precisely to counter opinions like the one presented 2 posts above

[Margie]

Not only were Katrina's sustained winds no higher than Cat 3, the surge, except for an *extremely* small area of coastline, was Cat 3 as well. The storm tide included approx two feet of high tide on top of the surge along most areas of the MS Gulf Coast, and for the few areas that received slighly higher surge, it was a moot point, because they were all right along the shoreline, and were hit with large battering waves on top of the surge.

Because the MS Gulf Coast is a tidal plain, a Cat 3 surge can go very far inland. The area of Cat 3 surge was so extensive -- unprecendented, really -- because Katrina was such a large storm.

I believe Katrina and Camille to be similar in many ways, and that the more detailed understanding we have of Katrina can also lead to a better understanding of Camille's structure. I suspect Camille may have also had a degradation of winds to the west and a broadening of the wind gradient to the east, because of the widespread but not severe wind damage that occured in Pascagoula. And if you remember the roadway sections of the Ocean Springs Biloxi Bay bridge were moved around with Camille to where you could just barely drive across it with the help of plywood or whatever it was they laid down between some of the sections, just not knocked clear off the supports as with Katrina, and likely the difference in height of the surge, and the larger waves from Katrina, made that difference, but it is probably not as large a difference as you might think.

[Margie]

Katrina was only a three? No way, it had barometric pressure of cat 5 storm and judging by the damage theres NO WAY that thing was a three.

From the post TC report on Katrina:

"The relatively weak winds in Katrina for such a low pressure are the result of the broadening pressure field on 29 August that spread the pressure gradient over a much larger than average distance from the center, as confirmed by both surface and aircraft observations. The generally weakening convection likely also reduced momentum mixing down to the surface, contributing to surface winds being less than what the usual 90% adjustment from flight level winds would dictate. Katrina exemplifies that there is not simply a direct one-to-one relationship between the central pressure and the maximum sustained winds in a hurricane."

Also, the wind damage was consistent with a Cat 3.

Katrina should be remembered. This is what a Cat 3 does! This is the level of damage that can occur with a Cat 3 (mostly surge damage rather than wind damage, in a tidal plain). There is no need to 'supersize' hurricanes in your mind to Cat 4 or 5, as a way to justify the damage. A large, high-end Cat 3...bad enough.

[Pearl River]

Derek, I believe hurricane force winds extended only 60 miles out in Camille. In Slidell we had a wind gust of 160 mph and we were in the western eyewall.

[Derek Ortt]

60 miles would make Camielle roughly the size of Ivan then.

was the 160 gust in Slidell from Camielle or Katrina? And if Camielle, what type of anamometer. If its hot wire, you may want to multiply by .65 to get the real wind speeds, as that was the reduction needed to get a real gust from keesler AFB from Georges, as its hot wire anamometer measured a gust to 172 m.p.h., when the real gust was about 123 (explains the 229 gust from Camielle, may have been closer to 140)

[Normandy]

60 miles would make Camielle roughly the size of Ivan then.

was the 160 gust in Slidell from Camielle or Katrina? And if Camielle, what type of anamometer. If its hot wire, you may want to multiply by .65 to get the real wind speeds, as that was the reduction needed to get a real gust from keesler AFB from Georges, as its hot wire anamometer measured a gust to 172 m.p.h., when the real gust was about 123 (explains the 229 gust from Camielle, may have been closer to 140)

Wats the inland gust ratio that Alskahuna always talks about? If I remember correctly, he said something like a 100 mph hurricane can produce 150 mph gusts over land due to the friction.