Katrina H-Wind Analysis, marginal 3 at landfall

[Brent]

It's hard for me to tell what intensity this was because along the coast everything was destroyed by the surge, I will say this, I didn't see the type of wind damage we saw after Charley or Andrew, which pretty much told me if it was a 4, it was a low end 4, HOWEVER, I also didn't see any wind damage AT ALL from the 1st landfall, so that above just pertains to the MS coast. If someone has pictures of Cat 4 wind damage in MS I'd love to see them.

When I have time to get them developed I will be happy to. I was an adjuster for a long time and I know the difference between storm surge damage and wind damage further inland.

FWIW, some of the damaged homes along the coast of Pascagoula was also not only due to storm surge but also wind damage.

OK... I'm not down there so I don't know. What I've seen on TV is relatively limited. My main issue was not being able to tell what damage was caused by surge and what was caused by wind.

[Derek Ortt]

the dropsondes also indicated those wind speeds. I have looked at some of the actual sondes as well

what should be considered is that it does not take a 4 to cause horrific damage

[tallywx]

Then I really think some previous storms need to be readjusted. Surge aside, I don't think we can put Hurricane Fran and Opal of 1995, and Hurricane Jeanne of 2004, as also having "marginal cat 3 winds" at landfall. Sheer wind damage from those storms was miniscule compared to Katrina's. I tend to agree with Derek...a sustained 120 mph wind can do tremendous damage...just think how much wind that actually is. I think it's more a matter of revising old storms downward.

Or perhaps if some were to argue that those storms had cat 3 winds, but in tiny spots, like Opal with the one streak near the east end of Choctohatchee Bay, Fran near Camp LaJeune, and Jeanne near Hutchinson Island, the aerial extent of cat 3 winds should be discussed. A storm with 115 mph over a 2 square miles should not be considered an equal hit to one with 115 mph over 80 sq. miles.

[Lindaloo]

Did they not use dropsondes in Andrew?

[curtadams]

I sure hope some of the destruction goes away here when they officially
downgrade... (that would be cool!)

The damage is real. So are the wind measurements. The required conclusion is that sustained 100 knot winds (or perhaps associated gusts) can cause what people call Cat 4 damage.

Yeah, they said this same thing after Andrew who was a CAT4 right? They changed it 10 years later.

Yeah, but Andrew was recategorized primarily on - damage estimates. Since damage estimates are at best very poorly calibrated to wind speed that's circular reasoning. In any case even if Andrew was a Cat 5 he didn't generate Cat 5 sustained winds on the ground. Ground winds are substantially less than the 10 m winds used to determine categorization.

[Furious George]

Then I really think some previous storms need to be readjusted. Surge aside, I don't think we can put Hurricane Fran and Opal of 1995, and Hurricane Jeanne of 2004, as also having "marginal cat 3 winds" at landfall. Sheer wind damage from those storms was miniscule compared to Katrina's. I tend to agree with Derek...a sustained 120 mph wind can do tremendous damage...just think how much wind that actually is. I think it's more a matter of revising old storms downward.

Or perhaps if some were to argue that those storms had cat 3 winds, but in tiny spots, like Opal with the one streak near the east end of Choctohatchee Bay, Fran near Camp LaJeune, and Jeanne near Hutchinson Island, the aerial extent of cat 3 winds should be discussed. A storm with 115 mph over a 2 square miles should not be considered an equal hit to one with 115 mph over 80 sq. miles.

I have to agree. It is likely that a huge number of people experienced these CAT 3 winds since the storm was so large, whereas normally they're in a more confined area. However, if a CAT 3 can cause total devastation as we've seen, I'm thinking people should make very little distinction between a CAT 3, 4 and 5. I guess that's why they're called majors.

[quandary]

Just seems impossible that any storm with a minimum pressure of 918 regardless of the environmental, situational, weakening, etc, effects could possibly have maximum sustained winds of 120-125.

If you look at the pressure gradient of a storm like Typhoon Tip, how could it be so huge and yet have only a pressure of 870 then? What I mean to say is, yes Katrina was big, but it wasn't that big. Also, the environmental pressure might be low, but it wasn't that low. Environmental pressure can at best vary by 20mb? So 918 in really low environmental pressure would be the same as 938 in really high environmental pressure, but 938 in high environmental pressure is... high end Cat 4 or even Low end 5, ex Isabel.

[quandary]

Oh and multiple wind maxima. Emily had 3 wind maxima at 945mb and winds of 115. So drop the pressure down another 30mb... which would still correspond to winds of around 150.

No way to slice this pie.

[jasons2k]

There seems to be a common theme in this thread (and among others) that many just can't comprehend what a true Cat. 3 hurricane can do. The numbers don't lie folks. It does not take a Cat. 4 or 5 to cause massive devastation; that's why Cat. 3s are considered MAJOR hurricanes. I think Derek with his expertise knows a thing or two about this subject.

[cjrciadt]

There seems to be a common theme in this thread (and among others) that many just can't comprehend what a true Cat. 3 hurricane can do. The numbers don't lie folks. It does not take a Cat. 4 or 5 to cause massive devastation; that's why Cat. 3s are considered MAJOR hurricanes. I think Derek with his expertise knows a thing or two about this subject.

Right on target Cat3's are called major canes for a reason. The damaged I received from Charley was only Cat1 with Cat2 gusts, a Cat3 I would not have a place to live.

[Derek Ortt]

that is a very good point in that a large region had the 100KT winds for this, which means that an area got cat 3 winds for a VERY long time, unlike the typical cat 3 storm, which has about a 1 mile wide streak of cat 3 winds.

The one thing I did notice was the lack of re-enforced concrete buildings totally destroyed by the wind alone, which occurred in Charley, which H-Wind does have as a cat 4 with 123KT (no dropsondes for the last minute intensification made it into the analysis)

[loon]

There seems to be a common theme in this thread (and among others) that many just can't comprehend what a true Cat. 3 hurricane can do. The numbers don't lie folks. It does not take a Cat. 4 or 5 to cause massive devastation; that's why Cat. 3s are considered MAJOR hurricanes. I think Derek with his expertise knows a thing or two about this subject.

Hrm, don't the met's even have arguements over this data? Somebody must have been for Andrew to get changed. All I'm saying is if the only thing your are basing your argument on is that Derek brought the message to the table, your logic is flawed. He said himself in the original post he was just the messenger.

That being said, I partly agree with you that Cat 3's are Majors and the winds are probably more damaging than you would think.

[kevin]

Okay I don't understand the wild backlash against Derek or the data. Just because you observe damage you think is like a 4, doesn't mean that it was. Maybe your expectation of what a 4 is, is wrong. The only thing that can tell whether this storm was a cat 3 or cat 4 is data and observations.

I'll take scientific data over opinions any day of the week, especially when people seem so emotionally determined that the storm was such and such. People who are emotionally involved will disregard evidence against their position. Its just a human thing to do.

[jasons2k]

There seems to be a common theme in this thread (and among others) that many just can't comprehend what a true Cat. 3 hurricane can do. The numbers don't lie folks. It does not take a Cat. 4 or 5 to cause massive devastation; that's why Cat. 3s are considered MAJOR hurricanes. I think Derek with his expertise knows a thing or two about this subject.

Hrm, don't the met's even have arguements over this data? Somebody must have been for Andrew to get changed. All I'm saying is if the only thing your are basing your argument on is that Derek brought the message to the table, your logic is flawed. He said himself in the original post he was just the messenger.

That being said, I partly agree with you that Cat 3's are Majors and the winds are probably more damaging than you would think.

Yes you are correct; I'm sure there will be much debate in the future amongst mets over Katrina. I agree also his bringing it to the table isn't the sole basis for it being correct; maybe I should have worded my post differently.

On the flip side, someone saying Katrina was a 4 just because the damage they witnessed was horrific doesn't pass the bar either, especially if they have no basis to compare it to. After Rita, my neighborhood sure looked like a Cat. 1 or 2 hurricane ripped through with all the downed trees, but we had TS winds (60-65 mph gusts) at the most. My neighbor looking out the window and yelling "gosh it was awful, this could not have been just TS winds" hardly can be backed-up with any data.

[donsutherland1]

Interesting data. If I recall correctly, the eye wall values are subject to a possible margin error of +/- 20% and the rest of the storm at +/- 10%. If so, Katrina might have been a strong Cat. 3/low Cat. 4 storm at landfall. I'm not suggesting one way or another with regard to the AOML analyses, but will be interested in seeing what the NHC's preliminary report on Katrina states.

In any case, a large Category 3 hurricane can certainly cause far more overall damage than a small Category 4 storm.

[Derek Ortt]

one thing is, moist people that go through a major hurricnae, dont really go through a major hurricane

Port Arthur went through a hgih end cat 1 hurricane, it was Louisiana that went through a real major cane, and there is nothing left of areas such as Cameron. Katrina had a large region of cat 2 conditions, and a large region of cat 3

Personally, I initially was flabergasted that this was a 3 at Louisiana, but I will continue to look at the data objectively, as will NHC and they will make the official best track determination

[Frank P]

Really doesn't matter to me what they classify Katrina's wind velocities to be... 100 mph or 200 mph, it all basically irrevelant to those thousands of people who lost everything they had to a storm surge that had to be in the 30 to 35 foot range in certain locations... most of the most catastrophic damage that I saw was surge related... granted a plethora of building were severly damaged from the Cat 3 or 4 winds, pick your poision... but the catastrophic damage along the MS coast was SURGE related...

So what would have happened if Katrina did not weaken from the 175 mph winds that it achieve during it's run.. someone tell me what kind of surge would have occurred, 50 feet??? ... I'm not sure if we didn't max out of our surge potential from Katrina, I sure in the hell hope so.. at 30-35 feet... I'm no expert for sure... but I've got serious debris marks from surge on my pecan tree at 35 feet above MSL... measured. .... that could be the accumulation of surge and waves pounding my poor tree but still... that basically put water at the roof line of my second flood, of which the first floor is 20 feet above sea level....

I think this storm was NOT your typical major hurricane... I've been in major storms before... this is unlike anything I've seen, nor anyone I've talked to that are down here doing relief work that has seen the damage from other majors.... Katrina is setting a new bar for hurricane damage...

I was in Bay St. Louis today... the damage in the town is incredible and I didn't even get to the beach areas...

[Derek Ortt]

The surge would have likely been higher had this retained the 150KT at landfall, since there would have been a longer time for the winds to blow over the shelf waters, as extreme speeds

[jasons2k]

Aside from the surge, it seems the major delineation between Katrina and other storms is how widespread the damage/windfield was. Katrina isn't setting any windspeed records, despite how much more severe the damage is described by emergency workers, etc., from other storms. The damage in places like Punta Gorda last year was just as severe or worse, it was just in a more concentrated area. As Derek pointed out, most major hurricanes have only a very small area of Cat3+ winds. Katrina happened to have these winds over a very wide area, hence the impression that it was more intense even if it wasn't. The wind damage may have been more widespread, but not necessarily more intense. Size does not equal intensity, except in how effectively it creates surge.

[Scorpion]

Oh whats next Rita was a strong Cat 1 at landfall?? Give me a break. This was a Cat 4 hands down. Hurricanes don't weaken 50 knots over a little dry air intrusion. People are trying to say a 918 mb hurricane is a marginal 3?