Katrina H-Wind Analysis, marginal 3 at landfall

[f5]

those surge heights really only apply to the south Florida area, not the rest of the coast

then why do they use it for the rest of the coast just another example of how flawed the SS scale really is

[Valkhorn]

Either way, I live in Hattiesburg - 90 miles inland.

The NWS said winds were 100mph SUSTAINED here. And the damage also supports gusts to 120-135mph.

Since I watched it from my window I can pretty much guess winds really were that strong. I wasn't able to measure it but with roofs blown off by wind alone, trees snapped in two halfway from the ground, etc. the winds were pretty strong.

Also something I have to say about the wind speeds. Often the planes do not find the maximum sustained winds. Sometimes they do, sometimes they don't. So, its very well possible that some higher winds did work their way down in order to do some damage - and coupled with the very large size of this storm it would have taken a lot to get rid of it.

Just my two cents.

[WeatherEmperor]

the world may never know....

<RICKY>

[Javlin]

Katrina's storm surge looks like a CAT 5 went threw there entire TOWNS were flattened such as waveland,pass christian ect

That's why I'd classify Katrina as a Category 5 based on storm surge and pressure.

I know, I know. It's determined by sustained wind and sustained wind only. But let's be honest here, there is a HECK of a lot more to a hurricane than sustained winds.

If the pressure and storm surge far exceed the level of sustained winds, I see nothing wrong with bending the SS scale rules a bit.

I got to take my first drive down 90 this afternoon it was unfathomable and beyond description.You are right f5 the damage along the beachfront is nothing less than a CAT 5+.The wind damage inland(one mile) I would say is a strong CAT 3 border weak CAT 4.I am definitly no pro just using the NHC's description of wind damage viva the Saffir Simpsion Scale.I really had a hard time seeing anybody surviving that surge.Oh by the way Broadwater Beach Marina was totally gone.It made it through Camille practially unscaved.It was marveled at the time after Camille as an engineering triumph History.

[Derek Ortt]

the SS scale descriptions are also wrong. Beaumont, which went through a very strong tropical storm or at worst a very marginal cat 1 hurricane, had damage consistent with a borderline cat 2/3, while Cameron was obliterated, where real cat 3 conditions occurred.

I think the reason why the SS was wrong is that back then, they did not have the doppler data available to show that in most cases, definately not Katrinas, the region of maximum winds is very, very small and most areas do not experience them, but about 2-3 categories less

[Frank P]

Yeah I concur with that Jav... we drove from Biloxi to Long Beach... the damage is incredible... practically every home on the beach and inland for several blocks in some areas are just gone.. I saw large barges inland at least two blocks or more in west Gulfport... so many beautiful homes are just slabs... its the most incredible thing I have ever seen... and even more incredible this storm makes Camille seem like a none event.... TV and pictures just don't do the incredible damage justice...

[Javlin]

the SS scale descriptions are also wrong. Beaumont, which went through a very strong tropical storm or at worst a very marginal cat 1 hurricane, had damage consistent with a borderline cat 2/3, while Cameron was obliterated, where real cat 3 conditions occurred.

I think the reason why the SS was wrong is that back then, they did not have the doppler data available to show that in most cases, definately not Katrinas, the region of maximum winds is very, very small and most areas do not experience them, but about 2-3 categories less

I agree derek my main point about the marina was how the surge just totally destroyed it.This mifht lend something to the winds is that alot of the newer houses are being built with Gables.Thus they do appear to have more destruction and definitly anything up 20-25 feet in height got hammered.My house has a 15' pitch on the roof she's 45 years old though I lost 2 bundles of shingles.My adjuster did say yesterday hat off to the roofer.About 70% of the houses on my block suffer alot worst than me.

[docjoe]

Pine would be the first to go.

Not necessarily; it is often opined that pines go first because they are not a hardwood tree. Actually pines are very flexible up to a point, and they have a deep root system. We have mostly pine trees here, yet there are many more oaks trees down than pines in this area of after Rita.

For the most part, the pine trees "held up" rather well. It's the oaks, especially water oaks, that took it badly.

I live about 10-11 miles from the GOM as the crow flies so I got quite a hit from both Ivan and Dennis. While they both leveled trees of all types all over the place I did notice that during Ivan most of my downed trees were pines and cedars with very few oaks. During Dennis I lost primarily oaks and hardwoods with much less damage to the pines and cedars. For my area Ivan was an extended period of hours of probably high Cat 1 to low Cat2 winds with higher gusts while Dennis brought a short period (probably an hour at most) of high cat 2 to low cat 3 . I wonder what role this plays in the type of tree damage. Of course the fact that alot of trees were weakened during Ivan played a role during Dennis.

docjoe

[yzerfan]

Also all oaks were not created equal. A healthy live oak can hold up through just about anything. Seems like most of the trees left along the MS coast are live oaks.

Other oaks, not so much. The state extension offices here will tell you not to plant laurel oaks because they will go down in even moderate hurricane force winds. Water oaks aren't quite so bad, but still nowhere close to as sturdy as healthy live oaks.

Same goes for different types of pine trees. The native longleaf pines in my area hold up a lot better in storms than the shortleaf pines that were planted in my town during the turpentine plantation days. We had many tons of trees in town do down during Ivan. I'd guess about 75% of the ones that did were shortleaf pine, and less than 5% longleaf pine.

[tallywx]

I think a main point of contention here is that we have a misperception of what kind of wind produces a particular level of damage.

Saying that "well, winds must have been cat 3 because of such and such type of damage" or "it looked outside to be winds of such and such strength" doesn't prove much, because it's not like we have an everday benchmark to base these estimations. How can one tell if winds were sustained at 100 v. 120 mph if one has never seen winds of either strength before? Similarly, how can we assume that a particular level of damage we associate with 115 mph sustained winds can't in fact be caused by 90 mph sustained winds? We have no solid basis! All we have is an outdated Saffir Simpson scale that in all likelihood overestimates the amount of wind it takes to cause particular damage.

It's not as if wind tunnel tests have been done on entire towns. If we could place a town inside a wind chamber, crank it up to 75, 85, 100, etc., then we would know for sure how to correlate a particular windspeed with a particular level of damage. All we have now is an antiquated scale that is being proven inaccurate by new technologies, such as SFMR.

Instead of saying SFMR is inaccurate because "winds of x speed can't cause that damage because...well, THEY JUST CAN'T," why instead not go the other direction...to consider this new revelation that it takes less wind than previously assumed to create damage of this level?

[tallywx]

Adding to my comment about the Saffir-Simpson scale...it was not based on rigorous tests in control laboratories. It was based on damage observations after storms considered to be of a certain strength. Example: Hurricane Zulu hits Mobile, AL. 1950s aircraft recon., using flight level wind measurements and assuming NO REDUCTION FROM FLIGHT LEVEL TO SURFACE, says Zulu hit with 115 mph winds. Furthermore, it is then assumed that all areas within the direct path of Zulu received 115 mph, rather than say in isolated spots (and SFMR is currently showing that max. sustained winds of a storm are not as pervasively widespread as previously thought). All of a sudden, we've designed a scale that overestimates windspeed on a dual level, by a) having the hurricane overrepresented in its overall intensity because we didn't know that flight level reduction of speeds were required, and b) overestimating the aerial extent of the absolute max. winds of a hurricane. In other words, a certain point in Mobile with a certain level of damage used to base the Saffir Simpson scale as correlated with 115 mph winds may have in fact only received 100 mph. In that case, the scale was miscalibrated.

New evidence in recent years is demonstrating this quite clearly.

So instead of not accepting new rock-solid data because of preconceptions based solely on historical antiquities rather than cold hard science, we should instead overhaul our perception of what a 100 mph wind looks like, or what a 100 mph wind can do.

[kevin]

Adding to my comment about the Saffir-Simpson scale...it was not based on rigorous tests in control laboratories. It was based on damage observations after storms considered to be of a certain strength. Example: Hurricane Zulu hits Mobile, AL. 1950s aircraft recon., using flight level wind measurements and assuming NO REDUCTION FROM FLIGHT LEVEL TO SURFACE, says Zulu hit with 115 mph winds. Furthermore, it is then assumed that all areas within the direct path of Zulu received 115 mph, rather than say in isolated spots (and SFMR is currently showing that max. sustained winds of a storm are not as pervasively widespread as previously thought). All of a sudden, we've designed a scale that overestimates windspeed on a dual level, by a) having the hurricane overrepresented in its overall intensity because we didn't know that flight level reduction of speeds were required, and b) overestimating the aerial extent of the absolute max. winds of a hurricane. In other words, a certain point in Mobile with a certain level of damage used to base the Saffir Simpson scale as correlated with 115 mph winds may have in fact only received 100 mph. In that case, the scale was miscalibrated.

New evidence in recent years is demonstrating this quite clearly.

So instead of not accepting new rock-solid data because of preconceptions based solely on historical antiquities rather than cold hard science, we should instead overhaul our perception of what a 100 mph wind looks like, or what a 100 mph wind can do.

*claps*

[jrod]

Well if a panel of experts say this was 'only' a cat 3 at landfall, I can not fathom what a cat 5 will bring.

I do think that quite a few storms, none of the bringing mass destruction, have been over estimated. And I do believe that extreme surge can follow a weakening storm, this was the case for Isabel in '03. The winds at landfall did not support a huge surge even, yet she carved some inlets through the Outer Banks.

[jasons2k]

Pine would be the first to go.

Not necessarily; it is often opined that pines go first because they are not a hardwood tree. Actually pines are very flexible up to a point, and they have a deep root system. We have mostly pine trees here, yet there are many more oaks trees down than pines in this area of after Rita.

For the most part, the pine trees "held up" rather well. It's the oaks, especially water oaks, that took it badly.

I live about 10-11 miles from the GOM as the crow flies so I got quite a hit from both Ivan and Dennis. While they both leveled trees of all types all over the place I did notice that during Ivan most of my downed trees were pines and cedars with very few oaks. During Dennis I lost primarily oaks and hardwoods with much less damage to the pines and cedars. For my area Ivan was an extended period of hours of probably high Cat 1 to low Cat2 winds with higher gusts while Dennis brought a short period (probably an hour at most) of high cat 2 to low cat 3 . I wonder what role this plays in the type of tree damage. Of course the fact that alot of trees were weakened during Ivan played a role during Dennis.

docjoe

Yes, there are probably a number of factors involved. If the winds here during Rita were higher than they were, the pines would have snapped/fallen in large quantities. But with the 45-50 G65 mph winds we had they just swayed, but many weaker oaks broke in half or blew over. I didn't see any damage to Live Oaks. I saw a Sweet Gum or two that blew over, but luckily not the one in my front yard.

[f5]

another problem with the SS scale just beacuse a hurricane weakens from a CAT to a CAT 4 does not mean the Surge weakens on the dime

[f5]

Well if a panel of experts say this was 'only' a cat 3 at landfall, I can not fathom what a cat 5 will bring.

I do think that quite a few storms, none of the bringing mass destruction, have been over estimated. And I do believe that extreme surge can follow a weakening storm, this was the case for Isabel in '03. The winds at landfall did not support a huge surge even, yet she carved some inlets through the Outer Banks.

to these experts a true CAT 5 means Armageddon destruction

[Derek Ortt]

in a true cat 5, like Andrew, the wind itself can obliterate anything. Homestead was totally leveled nearly to the extent of the Mississippi Coast due to the wind. In a true strong 4, like Charley, a very similar fate befalls the ladfall zone. Remember, that is a prolonged strong F2 or F3 tornado. IN Katrina, what we had according to the H-Wind analysis is a prolonged F-1 tornado, still VERY devastating on its own, just not quite as devastating as an Andew, Charley, or Iniki from a wind standpoint

[dhweather]

Check out this radar loop of Katrina making landfall. It was taken from the Mobile radar. Granted, the radar beam was viewing a high level in the storm. Notice the burst of deep convection in the northern and eastern eyewall just as Katrina makes landfall in Mississippi.


http://www.atmo.arizona.edu/products/radar/kat_mob_rad.gif

This convective burst likely produced winds well in excess of 100KTS. If any of you doubt it take a ride over to Diamondhead and check out the wind damage.......MGC

No need to ride over, I'm here.

[wxmann_91]

in a true cat 5, like Andrew, the wind itself can obliterate anything. Homestead was totally leveled nearly to the extent of the Mississippi Coast due to the wind. In a true strong 4, like Charley, a very similar fate befalls the ladfall zone. Remember, that is a prolonged strong F2 or F3 tornado. IN Katrina, what we had according to the H-Wind analysis is a prolonged F-1 tornado, still VERY devastating on its own, just not quite as devastating as an Andew, Charley, or Iniki from a wind standpoint

Question: what do you think is more destructive, Cat 5 winds or Cat 5 surge?

[Recurve]

IMO, there's good reason when they say "Run from water, hide from wind."
If you are in a surge zone in a Cat 5, you...will...die. Even in a 10-story condo tower, you might die if the whole thing crumbles from being undermined.

People survived Cat 5 Andrew winds in their bathtubs, even if that was the only thing left -- though people were also killed by beams crashing on them, but surprisingly few. The surge washed the desks and walls and everything else out the second floor at Burger Kind headquarters on the bay, a huge office building.