Katrina H-Wind Analysis, marginal 3 at landfall

[Matt-hurricanewatcher]

To be truthful it could of went from 160 mph to a 70 mph tropical storms. From 6 hours when its a cat5 120 miles off shore intill landfall as a 70 mph tropical storm. It would for one have the surge of a cat5 hurricane. But the winds 1 minute would be only 70 mph. Also the gust would likely be a good amount stronger. So for one you would see miles over miles of surge/wave damage inland. With out any damaging winds. So yes even if this thing got blown to the moon the last hour or so before landfall. Not much would of changed.

[Derek Ortt]

The advisory intensity is NOT the official intensity, the best track is. Remember, NHC said Floyd was a borderline 4/5 at Eleuthra, but BT showed it as a moderate 3 with 105KT winds. Floyd they had it as a borderline 3/4 at landfall in Alabama, but BT the debate was 100 or 105

Advisory intensities are ESTIMATES to ONLY be used in real time. All scientific papers reference the BT

[wxmann_91]

The advisory intensity is NOT the official intensity, the best track is. Remember, NHC said Floyd was a borderline 4/5 at Eleuthra, but BT showed it as a moderate 3 with 105KT winds. Floyd they had it as a borderline 3/4 at landfall in Alabama, but BT the debate was 100 or 105

Advisory intensities are ESTIMATES to ONLY be used in real time. All scientific papers reference the BT

I think you mean Ivan.

Yes, we know that the Best Track is what the scientific community uses, but what I mean is that I just don't see how they can revise the Best Track intensity at LA/MS landfall to anything less than a major hurricane.

[timNms]

Category Three Hurricane:
Winds 111-130 mph (96-113 kt or 178-209 km/hr). Storm surge generally 9-12 ft above normal. Some structural damage to small residences and utility buildings with a minor amount of curtainwall failures. Damage to shrubbery and trees with foliage blown off trees and large trees blown down. Mobile homes and poorly constructed signs are destroyed. Low-lying escape routes are cut by rising water 3-5 hours before arrival of the center of the hurricane. Flooding near the coast destroys smaller structures with larger structures damaged by battering from floating debris. Terrain continuously lower than 5 ft above mean sea level may be flooded inland 8 miles (13 km) or more. Evacuation of low-lying residences with several blocks of the shoreline may be required. Hurricanes Jeanne and Ivan of 2004 were Category Three hurricanes when they made landfall in Florida and in Alabama, respectively.

Wow, bout describes what happened here during Katrina. Some trees were almost completely bare of foilage. Now one can see the strangest thing. Spring colors in Autumn! Trees are putting on new leaves in early October!!

Question: note the "storm surge" mentioned in the description. Wonder if NHC will consider upgrading Katrina based on surge alone?

edited to add link: http://www.nhc.noaa.gov/aboutsshs.shtml

[Ivanhater]

The advisory intensity is NOT the official intensity, the best track is. Remember, NHC said Floyd was a borderline 4/5 at Eleuthra, but BT showed it as a moderate 3 with 105KT winds. Floyd they had it as a borderline 3/4 at landfall in Alabama, but BT the debate was 100 or 105

Advisory intensities are ESTIMATES to ONLY be used in real time. All scientific papers reference the BT

I think you mean Ivan.

Yes, we know that the Best Track is what the scientific community uses, but what I mean is that I just don't see how they can revise the Best Track intensity at LA/MS landfall to anything less than a major hurricane.

and i dont see how track intensity can be any less than a major with ivan

[jazzfan1247]

Nobody's saying that Katrina was less than a major hurricane; the data doesn't support that; or that it was less than a 3, although from the data it's not far from it.

[MGC]

Then why the downgrade when best track is published? Is the data from recon not accurate? Why put out an advisory that grossly over states the wind intensity? If a sonde measures XYZ winds during a pass, it gets used in an advisory and then thrown out months later during reanalysis. This makes little sense to me......MGC

[Derek Ortt]

not all of the data is available in real time

what is often done in real time, is they use the highest possible wind speed as reported by the data, which was 120KT based upon 134KT at flight level. The question is whether or not the mean 90% rule applied here, which careful analysis of the sondes and radar has showed that it likely does not.

One other aspect is that the best track uses quality controlled data. The real time data is not post processed to any great degree

[Droop12]

I think the NHC always overstates the wind alittle when a storm is approaching the coast just so people dont let their guard down which unfournately alot of people do. This is why we need to know the exact intensity of the storm so later on down the road people dont try to stay during a Cat 3 on the MS coast because they thought Katrina was a 5 and they'd be ok. Im sure there are at least a few misinformed people in LA or MS who believe they survived a Cat 5 which in fact they didnt. So if people can accept the fact Katrina made landfall as a Cat 3, they'll know the extreme amount of damage they can cause. This is exactly what Derek stresses.

[Aslkahuna]

Another reason for debating this is that some of you in this debate may some day find yourselves doing research on this very subject. Or as we say, welcome to the wonderful world of Meteorology.

Steve

[Weatherfreak000]

This debate IS worthless from a lesson gaining standpoint.



Andrew, a storm which was definitely at minimum a Cat 4 only caused a minimal storm surge, we all know where that damage came from. Katrina wouldn't even be on the news a month later in Florida. Their continental shelf brushes off even the most intense hurricanes with ease.


(Of course not saying coastline cities wouldn't recieve damage, but mind you New Orleans is pretty far inland).


In fact, i'd be damn near convinced to say the damage from this storm could be classified as something even far above Category 5 damage. A totally unprecented event that wiped out three states coastal areas PLUS New Orleans.



Bottom Line, New Orleans will build a significantly stronger levee system and no hurricane will ever produce these results again. Therefore the damage ratio will be pointless to comparsion.



No intensity lesson can be learned.

[jasons2k]

This debate IS worthless from a lesson gaining standpoint.



Andrew, a storm which was definitely at minimum a Cat 4 only caused a minimal storm surge, we all know where that damage came from. Katrina wouldn't even be on the news a month later in Florida. Their continental shelf brushes off even the most intense hurricanes with ease.


(Of course not saying coastline cities wouldn't recieve damage, but mind you New Orleans is pretty far inland).


In fact, i'd be damn near convinced to say the damage from this storm could be classified as something even far above Category 5 damage. A totally unprecented event that wiped out three states coastal areas PLUS New Orleans.



Bottom Line, New Orleans will build a significantly stronger levee system and no hurricane will ever produce these results again. Therefore the damage ratio will be pointless to comparsion.



No intensity lesson can be learned.

I couldn't disagree more with just about everything you said, except the narrow shelf off FLA does mitigate massive surges, but I wouln't say they are "brushed with ease".

Other than that, you've got to be kidding.

No hurricane will ever produce these results again? The damage ratio is pointless? My goodness, have you not read any of the previous 26 pages in this thread?

[f5]

Category Three Hurricane:
Winds 111-130 mph (96-113 kt or 178-209 km/hr). Storm surge generally 9-12 ft above normal. Some structural damage to small residences and utility buildings with a minor amount of curtainwall failures. Damage to shrubbery and trees with foliage blown off trees and large trees blown down. Mobile homes and poorly constructed signs are destroyed. Low-lying escape routes are cut by rising water 3-5 hours before arrival of the center of the hurricane. Flooding near the coast destroys smaller structures with larger structures damaged by battering from floating debris. Terrain continuously lower than 5 ft above mean sea level may be flooded inland 8 miles (13 km) or more. Evacuation of low-lying residences with several blocks of the shoreline may be required. Hurricanes Jeanne and Ivan of 2004 were Category Three hurricanes when they made landfall in Florida and in Alabama, respectively.

Wow, bout describes what happened here during Katrina. Some trees were almost completely bare of foilage. Now one can see the strangest thing. Spring colors in Autumn! Trees are putting on new leaves in early October!!

Question: note the "storm surge" mentioned in the description. Wonder if NHC will consider upgrading Katrina based on surge alone?

edited to add link: http://www.nhc.noaa.gov/aboutsshs.shtml

Katrina went to town with the storm surge as to rebuilding NO how about rebuilding those wetlands so those Hurricanes can weaken just a tad before geeting to NO.If NO becomes a beachside resort to the GOM those canes are going to make a visit with full force

[oneness]

This debate IS worthless from a lesson gaining standpoint.

How so? A lot of people clearly have learned lessons and gained experience, and stated as much.

Andrew, a storm which was definitely at minimum a Cat 4 only caused a minimal storm surge, we all know where that damage came from. Katrina wouldn't even be on the news a month later in Florida. Their continental shelf brushes off even the most intense hurricanes with ease.

I don't follow this, a minimum Cat 4? Andrew was at least a strong Cat 4, and is considered to probably have been a minimal cat 5. Continental shelves do not "brush-off" hurricanes. Every circumstance is different and every storm is different, so to generalise in that sort of way quickly becomes mythic and irrelevant.

(Of course not saying coastline cities wouldn't recieve damage, but mind you New Orleans is pretty far inland).

Look at the SE LA map. N.O. is very close to the GOM on the E and SE side, but regardless, the topography is both low and flat, offering little resistance to winds and water. It's quite doable for a genuine Cat 4 to cross over N.O. at genuine sustained wind intensities of a cat 4. Even a genuine Cat 3 N-E eye-wall within the city itself could easily put Katrina's damage level to shame.

In fact, i'd be damn near convinced to say the damage from this storm could be classified as something even far above Category 5 damage. A totally unprecented event that wiped out three states coastal areas PLUS New Orleans.

There's no such thing above Cat 5 as Cat 5 has no upper bound. It’s not possible to surpass total catastrophic structural wind damage. Katrina had measured Cat 3 winds and was nowhere near Cat 5 at landfall. What you see is what a large Cat 3 does. Face it.

Bottom Line, New Orleans will build a significantly stronger levee system and no hurricane will ever produce these results again. Therefore the damage ratio will be pointless to comparsion.

Nonsense, such an uber-levee system will not exist which could not be breached by a Hurricane. It's not just the overall intensity which matters, it’s the speed of it’s forward movement and the precise concentration of the maximum winds and water which matters. If a confluence of circumstances comes together in just the right combination no new levee will withstand it. You need to look at detailed large-scale before and after aerial photo surveys of major storms (not via satellite images, those show you very little) of how much a real Cat 3 can erode a shoreline. Not even a 40 ft earth levee could survive a Cat 3 in the right place at the wrong time.

No intensity lesson can be learned.

If you're prepared to face facts, then lessons will be learned. The facts here seem to be that in the period from about sunset on the 28th of August (and particularly from ~2 AM until about the 10 AM full landfall), Katrina progressively decayed and transitioned into a mid to lower Cat 3 storm. That resulted in a dramatically weakened western core which passed over east NO, causing remarkably light wind damage. The extraordinarily large and still very intense, but progressively weakening eastern core of the storm remained over-water for most of its transit to landfall proper, NE of N.O.

i.e. the storm's wind strength distribution and thus wind effects were highly asymmetric, and weakening, just as communities and cities became directly affected.

Had this not been the case, then things like sudden levee overtopping or complete levee failure could have occurred during this particular storm, and most of the structures in No far more severely damaged, (even via wind alone).

My own view is that cyclone lessons can be learned, but that they are usually only learned after first-hand experiences. Even raw video doesn’t convey much.

If the first-hand experience gained was of a large, mature, but rapidly weakening mid to low Cat 3, but you’re under the false or mythical impression that your direct experience was of a high-order Cat 4, then nope, you probably won’t be able to take on-board the lesson. If a person, or a wider community does not pay full attention to the details and implications of a lesson, then the lesson can not be learned and acted upon. My hope is that all urban planners and engineers are paying the necessary attention because now is the time to make serious changes to where people are permitted to build homes, and where major economic infrastructure items are allowed to be placed (even if that means resuming large tracts of private tenure land at significant expense), plus enforcing new codes for structural design and seriously reviewing permitted building materials in such areas.

Over-estimating strengths of recent and historical storms (as has demonstrably been the case) causes serious perceptual problems in a vulnerable community and actually enhances non-preparedness and denial of the no-BSing variety of mature cyclonic storms. Thus, the hyping and over-estimating of strength of recent and historically weaker storms is actually leading to an under-estimation of what such storms can and will do, if they manage to get their acts together before land-falling.

For these reasons a thread like this one is important and I'm glad the initial poster was prepared to both begin the thread, and also sustain it (through its more silly moments). There is a need for many threads like this one so that the message gets through that large, and genuine Cat 3s (or higher) are rare, yes, but when they do hit a developed region, they will always completely devastate it, and that much of this devastation and disruption can be mitigated.

That message has to get through all the noise and hype. If coastal communities don’t question all previous practices and building ‘traditions’ and don’t actively seek-out smarter answers and more intelligent responses to hurricanes, but instead, become fatalistic, or affected by some silly Stoic false bravado ("we will rebuild it just like it was"! … etc.)—the refusal to be necessarily flexible and respond to facts and predictable re-occurrence—then yes, the lessons of the recent storms won’t be learned. Or at least, they won't be applied due to lack of administrative policy change support and electorate momentum toward such practical initiatives.

Hopefully it's not just going to be up to Joe/Jane public to learn the lessons, but that professionals will pay all necessary attention, then formulate and enforce codified changes and the long-term policy re-direction which can result in far less fatalities and minimise destruction and economic disruption, when a 'mere' (genuine) Cat 2 strikes solidly. Not to mention a no-BSing Cat 3 giant, like Katrina.

[f5]

Katrina CAT 5 surge which is a different animal from one that wasn't

[oneness]

Katrina CAT 5 surge which is a different animal from one that wasn't

The Category classification is based upon sustained cyclonic wind speed, so there's no formal Cat 5 surge-level.

Saffir-Simpson Cat 5 surge is described as, "...Storm surge generally greater than 18 ft above normal...", but even cat 3 wind-fields, over ideal benthic profiles and geography, can surpass this surge level.

It appears even Rita could have had an ~20 ft max surge level, and this storm had not been a Cat 5 for a long time prior to landfalling, and had been visibly weakening and becoming less organised all of the preceding day (in fact, was looking rather lack-luster an hour or two prior to landfall).

So, two examples where Cat 3s produced extreme surge levels, which actually equalled or greatly exceed the typical surge of a Cat 5’s sustained wind speed in less ideal surge conditions.

[THead]

omg........will this thread ever end?!

[f5]

Katrina CAT 5 surge which is a different animal from one that wasn't

The Category classification is based upon sustained cyclonic wind speed, so there's no formal Cat 5 surge-level.

Saffir-Simpson Cat 5 surge is described as, "...Storm surge generally greater than 18 ft above normal...", but even cat 3 wind-fields, over ideal benthic profiles and geography, can surpass this surge level.

It appears even Rita could have had an ~20 ft max surge level, and this storm had not been a Cat 5 for a long time prior to landfalling, and had been visibly weakening and becoming less organised all of the preceding day (in fact, was looking rather lack-luster an hour or two prior to landfall).

So, two examples where Cat 3s produced extreme surge levels, which actually equalled or greatly exceed the typical surge of a Cat 5’s sustained wind speed in less ideal surge conditions.

Katrina was 175mph hurricane that is different from one that had not been that strong

[oneness]

Katrina CAT 5 surge which is a different animal from one that wasn't

The Category classification is based upon sustained cyclonic wind speed, so there's no formal Cat 5 surge-level.

Saffir-Simpson Cat 5 surge is described as, "...Storm surge generally greater than 18 ft above normal...", but even cat 3 wind-fields, over ideal benthic profiles and geography, can surpass this surge level.

It appears even Rita could have had an ~20 ft max surge level, and this storm had not been a Cat 5 for a long time prior to landfalling, and had been visibly weakening and becoming less organised all of the preceding day (in fact, was looking rather lack-luster an hour or two prior to landfall).

So, two examples where Cat 3s produced extreme surge levels, which actually equalled or greatly exceed the typical surge of a Cat 5’s sustained wind speed in less ideal surge conditions.

Katrina was 175mph hurricane that is different from one that had not been that strong

It was also slow-moving and did not accelerate it's forward motion until the final 12 hours before landfall leaving plenty of time for water to heap-up between the NE core and the gulf coast, where it was trapped by the coastal protrusion of SE LA to the west. The GOM waters had to stack-up on the northern coast because it could not move to the W, SW or S, given the path the core took. The peak winds occurring a day earlier may have been a contributor but moreso the benthic geography and huge core's wide swath I suspect.

[Derek Ortt]

I think what is happening is that people do not want to accept the fact that it could have been far worse and want to believe that they went through the worst. We went through this very thing during the Ivan intensity debate last year

Dennis may have had the highest wind speed of all of the Gulf Coast hurricanes this year and had it have been larger, it almost certainly would have reached the coast as a 4. However, the core of Dennis was very small and the hurricane winds did not affect nearly as many as they did for Katrina. From Grand Isle to the mouth of Mobile Bay, the entire region experienced at least sustained cat 2 winds