Katrina H-Wind Analysis, marginal 3 at landfall

[jazzfan1247]

Dude, it was a Category FOUR gust 40 miles inland is the point. Take a zanex and collect your thoughts

Well I apologize if I misread it, but I was under the impression that you pointed out the 135 mph gust to support the Cat 4 landfall at MS. Why else would you point to a MS observation? But then a few messages later you said you supported a Cat 3 at the MS landfall...exactly what were you trying to say?

[Brett Adair]

Dude, it was a Category FOUR gust 40 miles inland is the point. Take a zanex and collect your thoughts

Well I apologize if I misread it, but I was under the impression that you pointed out the 135 mph gust to support the Cat 4 landfall at MS. Why else would you point to a MS observation? But then a few messages later you said you supported a Cat 3 at the MS landfall...exactly what were you trying to say?

I'm basically trying to say that a category 4 US secondary landfall is what occured in Plaquemines Parish. A very strong category 3/weak 4 looks quite obvious in MS north of I-10 given you cant tell what happened south of there because of the tidal surge.

[Huckster]

I think this discussion has gotten off track. Are we talking about the Louisiana landfall or the Mississippi landfall? If we're talking about a Mississippi landfall, then what windspeed are we talking about? 120? 130? What? Even if we're talking about 120 at landfall in Mississippi, I think it's conceivable that the storm may have weakened at least 15 mph from its first landfall in Louisiana, which would make it 135 mph. Even though eastern Louisian is very low and marshy, I find it hard to believe that Katrina could have made landfall as a cat. 3 in LA (let's say 130 mph) and still produced cat. 3 and possibly cat. 4 gusts all the way into the Jones/Forrest County area. Just a guess. If I'm wrong, then that would prove that SE Louisiana is even less effective at weakening hurricanes than I thought. By the way, someone mentioned a 114 mph wind gust 40 miles east of where the storm made landfall. There are no corroborating reports that back that up. Forty miles to the west of the eye at landfall in LA would probably only have yielded Cat. 1 gusts, possibly cat. 2.

Huckster....that was me who said the 114mph 40 miles west of landfall. Now that I measured it, it's actually 30 miles west. I stayed at our office building for the storm. It has 3' thick concrete walls and ceiling, and has bullet proof glass. It's built to withstand a hurricane. Our anemometer at the office broke on a 114mph wind gust.

Hey, what town or city was this in? The peak wind gust reported from Houma was only 60 kts. I don't know if there was only a partial record or not from Houma, but the latest Katrina report from NWS New Orleans only indicates 60 kts at Houma.

[Brett Adair]

Let me put it this way....my fiances grandmother lives in Moss Point, MS. Right off the Bayou Heron and there was a shrimp boat sitting in her drive way after this was over. The house was moved off its foundation and the waterline was invisible because it covered the entire structure. The water line was some 30 ft up in the treeline. Well, the 2-4 trees that were left standing in her yard that used to hold about 60.

[jazzfan1247]

I'm basically trying to say that a category 4 US secondary landfall is what occured in Plaquemines Parish. A very strong category 3/weak 4 looks quite obvious in MS north of I-10 given you cant tell what happened south of there because of the tidal surge.

Thank you for the clarification. My question is: What are you basing the cat 4 landfall in plaquemines on? I mean in my opinion there really isn't anything to judge the wind speed in plaquemines since everything was underwater, you can't even judge wind damage...the only thing that has any credibility is Derek's SFMR, dropsondes, wind velocity etc evidence.

It is certainly true though that we will never have to debate the scope and gravity of the devastation.

[NorthGaWeather]

I will be glad to see what Tim Marshall of stormtrack finds during his one year stay there.

As will I Brett, as will I.

[NorthGaWeather]

Dude, it was a Category FOUR gust 40 miles inland is the point. Take a zanex and collect your thoughts

Well I apologize if I misread it, but I was under the impression that you pointed out the 135 mph gust to support the Cat 4 landfall at MS. Why else would you point to a MS observation? But then a few messages later you said you supported a Cat 3 at the MS landfall...exactly what were you trying to say?

I'm basically trying to say that a category 4 US secondary landfall is what occured in Plaquemines Parish. A very strong category 3/weak 4 looks quite obvious in MS north of I-10 given you cant tell what happened south of there because of the tidal surge.

Hey Brett, wasn't hundreds of acres of trees downed near Laurel? I thought I had read that from an Alabama EMC team.

[jasons2k]

This was posted yesterday on Accuweather by a structural engineer:

"We've communicated about this before, but I will again tell you that you CANNOT rely on local info with regard to estimating winds from storms. I am a structural engineer, and I have spent the last ten years investigating storm-damaged structures, on-site, including every hurricane that has hit the country since 1994.

In every single case, the locals greatly overstate the winds. Every time. Rumors spread, amateur anemometers give bad data, and so on. In the case of Katrina, the exact data is not going to be easily gotten, because the surge destroyed the power sources at the time the winds were increasing.

I have been to the scene, as recently as yesterday. This was a surge event.

The latest structure I looked at was a house on piles, main floor 12 feet off the ground, on the west side of Gulfport. Two miles from the beach. Water line: 5 feet on the main floor, or SEVENTEEN feet off the ground.But almost no wind damage. A few shingles knocked off, a few roof leaks, and that's it. This is typical of what I've seen.

As you know, the winds lag the pressure in a storm. Well, the surge lags the winds. In Katrina, like Ivan before her, the SURGE was much higher than the winds, because the storm was much stronger at sea. Both were Cat 5's at sea...both lost the worst of their winds, but hit before the surge could die down some. The damage to the MS coast is bad, but is very much the result of the surge, not the winds. Charley had worse wind damage than Katrina, and that was with 145 max. sustained. There's no way that Slidell had a 176/194. I've been there, and I don't buy it."

[skysummit]

I think this discussion has gotten off track. Are we talking about the Louisiana landfall or the Mississippi landfall? If we're talking about a Mississippi landfall, then what windspeed are we talking about? 120? 130? What? Even if we're talking about 120 at landfall in Mississippi, I think it's conceivable that the storm may have weakened at least 15 mph from its first landfall in Louisiana, which would make it 135 mph. Even though eastern Louisian is very low and marshy, I find it hard to believe that Katrina could have made landfall as a cat. 3 in LA (let's say 130 mph) and still produced cat. 3 and possibly cat. 4 gusts all the way into the Jones/Forrest County area. Just a guess. If I'm wrong, then that would prove that SE Louisiana is even less effective at weakening hurricanes than I thought. By the way, someone mentioned a 114 mph wind gust 40 miles east of where the storm made landfall. There are no corroborating reports that back that up. Forty miles to the west of the eye at landfall in LA would probably only have yielded Cat. 1 gusts, possibly cat. 2.

Huckster....that was me who said the 114mph 40 miles west of landfall. Now that I measured it, it's actually 30 miles west. I stayed at our office building for the storm. It has 3' thick concrete walls and ceiling, and has bullet proof glass. It's built to withstand a hurricane. Our anemometer at the office broke on a 114mph wind gust.

Hey, what town or city was this in? The peak wind gust reported from Houma was only 60 kts. I don't know if there was only a partial record or not from Houma, but the latest Katrina report from NWS New Orleans only indicates 60 kts at Houma.

Huckster, that was in Covington, La.

[vbhoutex]

This was posted yesterday on Accuweather by a structural engineer:

"We've communicated about this before, but I will again tell you that you CANNOT rely on local info with regard to estimating winds from storms. I am a structural engineer, and I have spent the last ten years investigating storm-damaged structures, on-site, including every hurricane that has hit the country since 1994.

In every single case, the locals greatly overstate the winds. Every time. Rumors spread, amateur anemometers give bad data, and so on. In the case of Katrina, the exact data is not going to be easily gotten, because the surge destroyed the power sources at the time the winds were increasing.

I have been to the scene, as recently as yesterday. This was a surge event.

The latest structure I looked at was a house on piles, main floor 12 feet off the ground, on the west side of Gulfport. Two miles from the beach. Water line: 5 feet on the main floor, or SEVENTEEN feet off the ground.But almost no wind damage. A few shingles knocked off, a few roof leaks, and that's it. This is typical of what I've seen.

As you know, the winds lag the pressure in a storm. Well, the surge lags the winds. In Katrina, like Ivan before her, the SURGE was much higher than the winds, because the storm was much stronger at sea. Both were Cat 5's at sea...both lost the worst of their winds, but hit before the surge could die down some. The damage to the MS coast is bad, but is very much the result of the surge, not the winds. Charley had worse wind damage than Katrina, and that was with 145 max. sustained. There's no way that Slidell had a 176/194. I've been there, and I don't buy it."

If that is what the instruments reported, I don't understand why a Professional Engineer would even make a statement such as this. Were those "official" instruments?

[jasons2k]

My guess would be simply that the visible damage doesn't support the wind reports/rumors/whatever you want to call them. I have seen the Slidell numbers cited numerous times, but I don't know if they have been confirmed by anyone as an official and accurate reading.

Even the pictures posted on this thread of the surge itself does not show any wind damage in the Cat 4 or 5 range, really even a Cat. 3. In every surge photo I have seen of the houses, etc., that have been posted - all the houses still have roofs on them. They still, for the most part, have shingles. The windows are still intact (unless the surge washed them out).

It's pretty straighforward IMO that the documented wind damage doesn't support the inflated 'estimates' being posted.

I don't know the engineer that posted. It was posted on Bastardi's column via an email he posted so I have no way to verify his credentials. But what he is saying is consistent with the damage photos; it was by and large a surge event.

[dhweather]

Again...we are talking GUSTS here, not sustained winds. And 110-115 mph gusts can be caused by Cat 1 sustained winds.

And since when did dropsondes utterly fail? Did those fail during the storm? How about SFMR, did it suddenly stop working? How did we come up with the data then?

Man...give it up. If they downgrade Katrina, they'd need to downgrade many, many, MANY other storms. I have seen the damage...I have been there for weeks and weeks...and it's clearly cat 4 damage. I'm NOT talking about storm surge, I'm talking about 20-50 miles inland of homes and structures completely gone off their foundations. I don't believe that type of destruction is listed in the classification of Cat 1, 2, or 3 storms. People need to get off their @ss, get out from behind their computers, and get the hell down there to witness it for themselves. Stop listening to the news, stop looking at the pics on the net, and see it for yourself. The damage is very widespread, but there are very small areas of total devistation WELL inland, NOT from surge. I have done recovery for MANY other storms, and this is clearly the worst I have ever witnessed.

Yep, until you've been here, you wouldn't understand.

[jazzfan1247]

Yep, until you've been here, you wouldn't understand.

It is exactly this kind of statement that inspired me to post in the first place. I admit it, I'm not there, so I don't get the same emotional impact and I don't know how it FEELS like. Given that, I have to give considerable weight to the evidence that Derek has presented, because of it's SCIENTIFIC value. Say all you want about how strong you think Katrina was at landfall...you are entitled to your own opinion, but be aware that you are arguing against current scientific evidence.

Now, don't take this the wrong way, but I do agree with what jschlitz said. Yes, the damage is terrible even wind-wise, and there are homes here and there that exhibit severe damage, but based on the aerial shots, the wind damage didn't seem "impressive" enough to be called a Cat 4. There may be reasons for this other than Katrina being weaker than some people think, but again, this is just my amateur opinion, and I would still put more weight on the evidence Derek posted, given that it is far more objective. Though if I were willing to play the damage game others are, this is how I would see it.

[skysummit]

This is a ridiculous argument. People are losing a lot of credibility with this debate.

[jazzfan1247]

This is a ridiculous argument. People are losing a lot of credibility with this debate.

Why is this a ridiculous argument? Why are so many people here "scared" of finding out exactly how intense Katrina was at landfall? It's not like Katrina is gonna come back as a ghost because we offended her by saying she wasn't as strong as she would've liked us to believe. I just don't understand this, don't yall wanna know exactly how hard a storm hit, so that you don't get completely shocked when a similar storm hits with the same ferocity? This is what science is about, constant debating over the facts and evidence, and determining a conclusion from it. What harm comes from this?

I agree, people are losing credibility from this...the people who completely dismiss Derek's evidence without any similarly objective evidence of their own. You can disagree with his evidence, it's ok, but at least acknowledge the fact that it very well could be true. So many here have dismissed it without even putting ANY value on it, which really shouldn't happen if you've taken any science classes in school.

[jasons2k]

Jazzfan that is an excellent point and I think that brings it back to the root of the whole issue - and that is a Cat. 3 can cause incredible wind damage, the kind of wind damage that one's imagination could only associate with a Cat. 5 monster.

I saw Homestead after Andrew. I also spent a week on Big Pine, Cudjoe, and Ramrod Keys after Georges in 1998 with my father. I know this much, if I had not been to Homestead previously, I would have a very hard time believing they had Cat. 1 borderline Cat. 2 conditions there. It literally looked like a bomb went off and almost every tree taller than 20ft. was either snapped or blown over. EVEN STILL, it was NO comparison to Andrew.

[dhweather]

Yep, until you've been here, you wouldn't understand.

It is exactly this kind of statement that inspired me to post in the first place. I admit it, I'm not there, so I don't get the same emotional impact and I don't know how it FEELS like. Given that, I have to give considerable weight to the evidence that Derek has presented, because of it's SCIENTIFIC value. Say all you want about how strong you think Katrina was at landfall...you are entitled to your own opinion, but be aware that you are arguing against current scientific evidence.

Now, don't take this the wrong way, but I do agree with what jschlitz said. Yes, the damage is terrible even wind-wise, and there are homes here and there that exhibit severe damage, but based on the aerial shots, the wind damage didn't seem "impressive" enough to be called a Cat 4. There may be reasons for this other than Katrina being weaker than some people think, but again, this is just my amateur opinion, and I would still put more weight on the evidence Derek posted, given that it is far more objective. Though if I were willing to play the damage game others are, this is how I would see it.

I'm not emotional about it at all.

I see water lines 35 feet above MSL. That's not emotion, that's fact.
If you want to call a tape measure scientific, then so be it.

I see palm trees snapped in the middle. That's typical of 4/5 winds.

My anemometer was destroyed early on by debris. So was the
anemometer at the Diamondhead Fire department, which failed at 144 MPH.

I see rooftop structures peeled off of condominiums and tossed like
leaves. This in an area 40-60 feet above MSL, so it's clearly a wind
event.

I see large number of trees leveled - gone.

Nothing personal here, but as I mentioned before, we went to war based
on satellite "intelligence". In hindsight, every intelligence agency stated
clearly that we needed on the ground intelligence for accurate information.

The same thing applies to this - satellite and radar loops only tell you so
much of the story. Coming here, looking at physical evidence, measure
debris lines, interview local officials, gather data from local weather stations.

I have yet to hear one person that was here for Camille, an agreed upon
Cat 5, say that Katrina was not as bad as Camille was.

All of this, yet we take the measurements from a guy that was knocked
out and woke up in a tree as the gospel without any reservation (1935
keys hurricane). Nobody questions the calibration of his instruments
or his personal observations. It's carved in stone.

[curtadams]

I'm not emotional about it at all.

I see water lines 35 feet above MSL. That's not emotion, that's fact.
If you want to call a tape measure scientific, then so be it.

I see palm trees snapped in the middle. That's typical of 4/5 winds.

My anemometer was destroyed early on by debris. So was the
anemometer at the Diamondhead Fire department, which failed at 144 MPH.

I see rooftop structures peeled off of condominiums and tossed like
leaves. This in an area 40-60 feet above MSL, so it's clearly a wind
event.

I see large number of trees leveled - gone.

The same thing applies to this - satellite and radar loops only tell you so
much of the story. Coming here, looking at physical evidence, measure
debris lines, interview local officials, gather data from local weather stations.

I have yet to hear one person that was here for Camille, an agreed upon
Cat 5, say that Katrina was not as bad as Camille was.

All of this, yet we take the measurements from a guy that was knocked
out and woke up in a tree as the gospel without any reservation (1935
keys hurricane). Nobody questions the calibration of his instruments
or his personal observations. It's carved in stone.

I'm all for measurements. Go out and photograph a measurement of a 35 foot surge mark. Trees aren't useful because of the wave issue. Best is inside a house. Measure a watermark and find some way to determine the house elevant.

Go photograph the roofs! I've seen hundreds of pics of Katrina on the MS coast and I've yet to see any wind damage incompatible with borderline Cat 3 or even strong Cat 2. Go get your scoop!

Palm trees can snap in considerably less than Cat 4. Ivan, a borderline Cat 3, snapped palms in Pensacola: http://www.palmbeachpost.com/storm/cont ... _0916.html

Large-scale tree downings can happen with F1 *gusts* according to the tornado damage scale. So even a tropical storm could theoretically do that.

I agree about the 892 in the Labor Day hurricane. An observation by *one* guy of an uncalibrated barometer well beyond its normal range is hardly definitive. I'd prefer that the LD hurricane be listed as "pressure unknown, unconfirmed report of 892 mb".

[Scorpion]

Is the debate whether this was a Cat 4 in MS or in LA? Certainly I think it was a strong 3 in MS and 120 kt or so at LA. Im sorry but when we see the HRD report saying Katrina was 112 kt with a 908 pressure I don't tend to believe it.

[Derek Ortt]

why do you not believe it? Any scientific basis for not believing it? It is VERY believable as the storm was 10KT more intense when the pressure was 10mb lower. The pressure gradient changed eased significantly in the few hours before landfall

The normal pressure to wind relation does not hold in the northern GOM

We have a 918mb cat 3 in all liklihood in Katrina, a very generous 105KT cat 3 Ivan at 946, a 100KT cat 3 Opal at 942, A 105KT cat 3 Dennis at 946, and a 90KT, 961mb cat 2 Georges