Katrina H-Wind Analysis, marginal 3 at landfall

[Jim Cantore]

cat 3 winds + Cat 5 surge

Cat 4 in my book

[timNms]

True, the other pro-mets weren't there at the scene, but they DO have access to objective data obtained by weather instruments that do not contain things such as human emotion, bias, etc. Even Derek said himself that he underestimated the winds when Katrina came through his area. Now, for all I know, your retired-met friend could be a perfect human being, capable of estimating sustained winds with an accuracy better than that of calibrated scientific instruments. But personally, I would go with the scientific instruments, and so should everyone else.

In the absence of other evidence, more weight would be put on such first-hand accounts as your retired-met friend, but the point is that we DO have better evidence, evidence that suggests that he overestimated the sustained winds, which from what I’ve read is really not very difficult to do. So yes, go ahead and ponder over his first-hand account, but be aware that less weight should be put on it compared to dropsonde data, radar data, etc.

Human observation can be a powerful tool, but there are certainly limits, and this is one of them. If we were so accurate, why don’t we use human observation to determine exact wind speeds at any given location? We don’t; we use weather instruments, quite simply because they are more accurate. The same principle applies here: the objective data is much more reliable than a biased, emotional observer who has observational limits as a human being.

And yes, I am aware of the Lake Charles station possibly underestimating the winds, but that is really quite rare. And in Katrina's case, we had not only SFMR, but also dropsondes and radar velocity...and multiple recon flights showing the same data. In my opinion, there's absolutely no way ALL of these underestimated the winds by a significant degree.

You are certainly entitled to your opinion, but sometimes scientific reasoning is not the only answer. If that were the case, then those who survey tornado damage would not rely on personal experience to estimate the windspeed. Until you have been there and seen the damage for yourself, you'll be inclined to rely on the "so-called" scientific evidence.

However, accusing a well educated man of being too emotional or inexperienced to do what he has been trained to do is rediculous. I'm pretty sure that he is intelligent enough to base his belief, that the surge was 40 feet, on the geography of the area in which he resided, and after surveying the damage, do an assesment of the strengh of the storm. I'm also sure he knows the difference between a 120 mph wind and a 145 mph wind.

[Derek Ortt]

scorpion,

recon does not support cat 4 at landfall

flight level is only a small part of recon and the 90% reduction is the MEAN, the range of 700mb reduction is 60-120%

as for the tornadoes, the method of analyzing damage is used because it is nearly impossible to obtain a true wind speed. Only a mobile doppler radar can do that, and those readings are few and far between. Damage is not considered to be an acceptable form of determinig wind speed in tropical meteorology, as I have been told many times by mets who have a PHD already

[timNms]

scorpion,

recon does not support cat 4 at landfall

flight level is only a small part of recon and the 90% reduction is the MEAN, the range of 700mb reduction is 60-120%

as for the tornadoes, the method of analyzing damage is used because it is nearly impossible to obtain a true wind speed. Only a mobile doppler radar can do that, and those readings are few and far between. Damage is not considered to be an acceptable form of determinig wind speed in tropical meteorology, as I have been told many times by mets who have a PHD already

I understand that, Derek. Was using it as an example. Also wondering if you are planning a trip to the area to get a first hand look. Another question for you. As I've heard many say, the pictures don't show cat 4 or cat 5 damage because all of the trees are not leveled or the houses are not missing roofs. Could that be because possibly they were covered by the surge?

[Scorpion]

If this was indeed a Cat 3 then Hurricane Jeanne and Dennis need to be looked at, as well as countless other hurricanes that made landfall. I find it ridiculous how a 908 mb hurricane can be a Cat 3.

[jazzfan1247]

You are certainly entitled to your opinion, but sometimes scientific reasoning is not the only answer. If that were the case, then those who survey tornado damage would not rely on personal experience to estimate the windspeed. Until you have been there and seen the damage for yourself, you'll be inclined to rely on the "so-called" scientific evidence.

However, accusing a well educated man of being too emotional or inexperienced to do what he has been trained to do is rediculous. I'm pretty sure that he is intelligent enough to base his belief, that the surge was 40 feet, on the geography of the area in which he resided, and after surveying the damage, do an assesment of the strengh of the storm. I'm also sure he knows the difference between a 120 mph wind and a 145 mph wind.

Well, the reason why this is is because there aren't enough wind instruments to cover every single tornado that occurs as it occurs...thus the need to base it off of a damage scale. That's the best we can do at this day in age. If we could somehow have wind instruments in every single tornado that occurred, would you rather base the intensity on the readings that these instruments indicate, or the damage that it caused? I know my answer...

Hurricanes are different...we can document with wind instruments what it does almost every step of the way (when it's close to shore). This is why the Saffir-Simpson scale is not damage-based. Now, whether we should have a damage scale for hurricanes...that's up for debate. Basically what I'm saying is that...if we CAN document the intensity of storm systems using reliable scientific instruments, than we should by all means take this data over any subjective evidence such as damage or first-hand accounts, since damage and personal accounts can be influenced by a variety of factors.

As for the second part, I'm just pointing out the flaws of human nature. We are not perfect as observational beings for some of the reasons I've stated. I don't want to debate the storm surge height, as I'm not qualified to do so, but as far as the wind speeds go, I have to go with what the scientific data currently suggests. And Derek himself has devoted tons of time researching tropical cyclones, so you would think that he would be able to accurately estimate winds just as that retired-met, but he didn't. Therefore, the retired-met could very well be wrong about his own observations, right?

[skysummit]

If this was indeed a Cat 3 then Hurricane Jeanne and Dennis need to be looked at, as well as countless other hurricanes that made landfall. I find it ridiculous how a 908 mb hurricane can be a Cat 3.

Yup....PLENTY of other hurricanes need to be downgraded.

[Derek Ortt]

Scorpion,

as many have told you, <b>MOST CAT 3'S HAVE A NARROW SWATH OF CAT 3 WINDS. THIS ONE HAD A LARGE REGION, AND 90KT SUSTAINED WINDS COVERED THE ENTIRE MISSISSIPPI COAST</b>

I suggest you, Scorpion, learn the equations of motion. I didnt understand meteorology at all, until I learned them

[timNms]

You are certainly entitled to your opinion, but sometimes scientific reasoning is not the only answer. If that were the case, then those who survey tornado damage would not rely on personal experience to estimate the windspeed. Until you have been there and seen the damage for yourself, you'll be inclined to rely on the "so-called" scientific evidence.

However, accusing a well educated man of being too emotional or inexperienced to do what he has been trained to do is rediculous. I'm pretty sure that he is intelligent enough to base his belief, that the surge was 40 feet, on the geography of the area in which he resided, and after surveying the damage, do an assesment of the strengh of the storm. I'm also sure he knows the difference between a 120 mph wind and a 145 mph wind.

Well, the reason why this is is because there aren't enough wind instruments to cover every single tornado that occurs as it occurs...thus the need to base it off of a damage scale. That's the best we can do at this day in age. If we could somehow have wind instruments in every single tornado that occurred, would you rather base the intensity on the readings that these instruments indicate, or the damage that it caused? I know my answer...

Hurricanes are different...we can document with wind instruments what it does almost every step of the way (when it's close to shore). This is why the Saffir-Simpson scale is not damage-based. Now, whether we should have a damage scale for hurricanes...that's up for debate. Basically what I'm saying is that...if we CAN document the intensity of storm systems using reliable scientific instruments, than we should by all means take this data over any subjective evidence such as damage or first-hand accounts, since damage and personal accounts can be influenced by a variety of factors.

As for the second part, I'm just pointing out the flaws of human nature. We are not perfect as observational beings for some of the reasons I've stated. I don't want to debate the storm surge height, as I'm not qualified to do so, but as far as the wind speeds go, I have to go with what the scientific data currently suggests. And Derek himself has devoted tons of time researching tropical cyclones, so you would think that he would be able to accurately estimate winds just as that retired-met, but he didn't. Therefore, the retired-met could very well be wrong about his own observations, right?

I won't argue with you about this. I think all we can do is wait for the official NHC findings and then draw conclusions based on that.
I know that Derek has devoted tons of time in doing research. The same can be said for the met who was there.

Regardless of the outcome of the research into Katrina, we all know that she was a monster who changed a lot of lives forever. Here's to the hope that no one has to go thru such a storm again!

[wxman57]

If this was indeed a Cat 3 then Hurricane Jeanne and Dennis need to be looked at, as well as countless other hurricanes that made landfall. I find it ridiculous how a 908 mb hurricane can be a Cat 3.

You make a good point, Scorpion. The 920 mb pressure at landfall (not 908) is certainly supportive of a stronger than Cat 3 hurricane, normally. It seems we've seen a lot of hurricanes this season with relatively low pressure but winds not matching. I know that the average pressure across the Gulf and Caribbean Sea have been lower than normal. Perhaps that partly explains it. Or it could be that the strongest winds were just not reaching the surface.

Another explanation, and perhaps a good one, is that no two hurricane's horizontal (and vertical) wind fields are the same. There are some Cat 3 hurricanes that have those Cat 3 winds only over a few square miles. Remember, the wind in the NHC advisory is not the average wind through the storm, but the MAXIMUM sustained wind in any one small area of the hurricane. Often, someone passing near the center of a Cat 3 actually saw only Cat 1 winds. You can't even stand up in Cat 1 winds. Cat 1 winds can destroy homes if they're not boarded up properly. In Cat 3 winds, you'd literally be blown away.

Go to the HRD web site and compare the horizontal wind field of, say, Lili in 2002 and Katrina. Katrina's 75+ mph wind field was about as big as Lili's entire circulation, yet both were near the same intensity. Pass 30-40 miles from Lili's center and you go through a tropical storm. Pass the same distance from Katrina and you go through 75-100 mph winds. That's 3-4 times the wind force at the same distance from the center in two similarly-classified hurricanes. It's very rare to experience sustained 75+ mph winds. Most people who've been through a hurricane haven't seen such winds. But Katrina produced such winds over a much larger than average area. In that respect, Katrina was a very unusual hurricane.

One thing I've noticed over the last 10-15 years is that the NHC is typically VERY generous with their wind estimates for landfalling hurricanes. They appear to be very reluctant to indicate any pre-landfall weakening on their advisories. So, in a number of cases, a landfalling hurricane may have actually had winds 10-20 mph (or more) lower than what was carried on the advisories. Those who think they went through a Cat 2 or a Cat 3 may have only seen a Cat 1 or a Cat 2 hurricane. The NHC has been over-warning people for quite a while. Now that some REAL Cat 3+ hurricanes are making landfall, the damage doesn't come close to matching what some pseudo Cat 3 hurricanes of recent years produced.

[dhweather]

A peak gust of 140mph would imply a sustained wind of 115 mph (100kt) or Cat 3 winds at Slidell. I haven't seen any of his Katrina video yet.

Steve

And the general rule that the winds will be 30MPH higher on the east side
(versus the west side) would extrapolate to 145mph or so. Dangerously
close to a cat 5.

[skysummit]

Yea...and we had 114mph gusts 40 miles WEST of landfall. I say 114mph, but that's when the anemometer broke.

[Brett Adair]

http://kamala.cod.edu/la/latest.acus74.KLIX.html

All of that supports a Category 4 at landfall. Whomever thinks was a marginal Category 3 will lose tons of credibility when this is all over. Which, it doesn't really matter what we think. The facts are there. The government will be decisive in this matter.

I agree with KNHC...Perry...and many other mets saying that Katrina was definately a strong 4. Most of the wind instruments were broken prior to peak readings in most cases.

[Aslkahuna]

Katrina was NOT moving fast enough for that kind of asymmetry in the windfield. You don't just automatically assume that the winds are 25 kt higher on the eastern side of the storm because they may not be. Also the 100kt estimate for surface winds assumes that the standard 1.25 gust ratio for over water is still applicable which it may not be. The sustained winds could have been 100 mph (85kt) just as easily. Or even less.

Steve

[Stormcenter]

If this was indeed a Cat 3 then Hurricane Jeanne and Dennis need to be looked at, as well as countless other hurricanes that made landfall. I find it ridiculous how a 908 mb hurricane can be a Cat 3.

The post of the day, thank you! I'm shocked that we continue to waste time debating the obvious. Katrina was at least a Cat.4 at landfall you can argue it until you are blue in the face but it is what it is.

[Stormcenter]

http://kamala.cod.edu/la/latest.acus74.KLIX.html

All of that supports a Category 4 at landfall. Whomever thinks was a marginal Category 3 will lose tons of credibility when this is all over. Which, it doesn't really matter what we think. The facts are there. The government will be decisive in this matter.

I agree with KNHC...Perry...and many other mets saying that Katrina was definately a strong 4. Most of the wind instruments were broken prior to peak readings in most cases.

Its nice to know that some people can see the obvious. Thank you.

[jazzfan1247]

http://kamala.cod.edu/la/latest.acus74.KLIX.html

All of that supports a Category 4 at landfall. Whomever thinks was a marginal Category 3 will lose tons of credibility when this is all over. Which, it doesn't really matter what we think. The facts are there. The government will be decisive in this matter.

I agree with KNHC...Perry...and many other mets saying that Katrina was definately a strong 4. Most of the wind instruments were broken prior to peak readings in most cases.

Exactly what part of that report supports a Category 4?

[MGC]

The closest offical wind recording site was at Stennis Airport in Kiln Mississippi. This site was in the eastern eyewall of Katrina. Have any of you seen any data from Stennis?......MGC

[Brett Adair]

http://kamala.cod.edu/la/latest.acus74.KLIX.html

All of that supports a Category 4 at landfall. Whomever thinks was a marginal Category 3 will lose tons of credibility when this is all over. Which, it doesn't really matter what we think. The facts are there. The government will be decisive in this matter.

I agree with KNHC...Perry...and many other mets saying that Katrina was definately a strong 4. Most of the wind instruments were broken prior to peak readings in most cases.

Exactly what part of that report supports a Category 4?

POPLARVILLE - PEARL RIVER COUNTY MS EOC PEAK 117 KT

135 mph supports a Category 4....especially with that reading coming some 40 miles inland.

B. LOWEST PRESSURE PRES MB TIME UTC ON AUGUST 29 2005 UNLESS NOTED SLIDELL NWS........... 934.1 1438 UTC

Looks like a category 4 pressure reading well inland as well. Catch up on your studdies.

[jazzfan1247]

If this was indeed a Cat 3 then Hurricane Jeanne and Dennis need to be looked at, as well as countless other hurricanes that made landfall. I find it ridiculous how a 908 mb hurricane can be a Cat 3.

The post of the day, thank you! I'm shocked that we continue to waste time debating the obvious. Katrina was at least a Cat.4 at landfall you can argue it until you are blue in the face but it is what it is.

How is this obvious? Derek has posted OBJECTIVE scientific analysis from instruments that have been tested over and over. And it's not just the SFMR, it's the dropsondes and the radar wind velocities too. And multiple flights show similar data. How can you make a claim that it's "obvious" this data was wrong? Unbelievable? Yes. Obvious that it's wrong? No...