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Katrina officially downgraded to a Category 3

By: Dr. Jeff Masters, 4:08 PM GMT on December 21, 2005

Today is winter solstice--the darkest day of the year--and an appropriate time to revisit America's other darkest day of the year, August 29. The National Hurricane Center (NHC) issued its official Tropical Cyclone Report for Katrina on Tuesday. Katrina officially made landfall as a Category 3 hurricane, not a Category 4. Ground-based and aircraft measurements only support 110 knot winds (127 mph) at Katrina's first landfall near Buras, Louisiana. Katrina weakened only slightly before her second landfall, and was still a Category 3 hurricane with 105 knot (121 mph) winds on the Mississippi coast. The NHC report also stated that the highest sustained winds over metropolitan New Orleans were only of Category 1 or 2 strength, although buildings over 25 stories high may have seen winds a full category higher.

The reason Katrina was originally classified as a Category 4 at landfall was because winds measured by the Hurricane Hunters at flight level (10,000 feet) were 150-155 mph. The normal rule of thumb used to estimate surface winds is a 10% redution from the winds at 10,000 feet. This rule of thumb was applied for the official NHC advisories issued at the time of Katrina's landfall, and made Katrina a Category 4 hurricane with 135-140 mph surface winds. However, detailed analysis of the wind structure of Katrina in data gathered by Doppler radar and dropsondes showed that at landfall, Katrina had its highest winds in an unusually strong band of winds between 2 and 4 km (the flight level of the Hurricane Hunters was about 3 km). Normally, the highest winds in a hurricane are found much lower, near .5 - 2 km. Surface winds measured by dropsondes, surface towers, and the SFMR microwave radiometer on the aircraft all agreed that the surface winds at landfall were no higher than 100 knots (115 mph). NHC adjusted these upwards by 10% to account for the fact that the strongest winds were likely not sampled. The 10% adjustment left Katrina just 5 mph shy of Category 4 status--but still a very potent and deadly major Category 3 hurricane.

The 10% reduction "rule of thumb" was not valid for Katrina at landfall, probably because the storm's convection was weakening at that time. Because momentum transport from aloft to the surface was impaired by the weakening convention, Katrina was less able to carry the strong winds that were aloft down to the surface. Thus, winds at the surface were about 80% of the winds measured at 10,000 feet. Still, NHC does mention that given the uncertainties and large wind field of Katrina, the very tip of the Mississippi Delta near Buras may have received Category 4 winds for a few minutes, and it is possible Katrina really was a Cat 4 at landfall.

Why Katrina weakened at landfall
At peak intensity, Katrina was a Category 5 hurricane with 150 kt (174 mph) winds, but in the 18 hours before landfall weakened to 110 kt (121 mph). This weakening occured as a result of entrainment of dry air into the storm, slightly cooler sea surface temperatures near the coast, and interaction with the land. NHC notes that the relative importance of these three factors cannot be determined without a lot more study, but all 11 hurricanes with pressures less than 973 mb that have hit the Gulf coast the past 20 years have weakened in the 12 hours prior to landfall. Thus, Katrina's weakening should come as no surprise. Note, however, that Hurricane Camille of 1969 did not weaken when it pounded Mississippi as a Category 5 hurricane; perhaps it's small size protected it from substantial land interaction and entrainment of dry air.

Storm surge
To me, the biggest disappointment in the report came in the treatment of Katrina's storm surge. No storm surge data was presented for New Orleans. No mention was made that Katrina, despite its Category 3 strength at landfall, pushed a Category 5 level storm surge to the coast. The report noted that official storm surge measurements were unavailable, due to failure of most of the tide gauges. However, one unofficial storm surge height of 27 feet at the Hancock County Emergency Management Office in Mississippi was mentioned, which would make Katrina's storm surge the highest on record for an Atlantic hurricane. The previous record was Hurricane Camille's 24.7 feet. Any surge above 18 feet is considered a Category 5 level storm surge. I've seen unofficial estimates that the storm surge affecting the eastern side of New Orleans was 18-25 feet high, which is clearly a Category 5 storm surge. Not surprisingly, the levees protecting the east side of the city were overwhelmed and failed in multiple locations. However, observational data and computer modeling indicate that storm surge entering the canals from Lake Pontchartrain reached 9 to 11 feet in the 17th Street Canal and 11 to 12 feet in the London Avenue Canal. The flood walls were 13.5 feet high or higher along much of the two canals and were designed to withstand water rising to 11.5 feet. A Category 3 storm surge is 9-12 feet, so these flood walls failed in a Category 3 level storm surge, even though they were supposedly designed to withstand that type of storm surge.

Pressure
Katrina officially made landfall at Buras, LA, with a central pressure of 920 mb. This is the third lowest pressure on record for a U.S. landfalling hurricane, surpassed only by the two Category 5 hurricane to hit the U.S.--the Florida Keys Labor Day Storm of 1935 (892 mb) and Hurricane Camille of 1969 (909 mb). Katrina had the lowest pressure ever measured for a Category 3 hurricane; the previous record was 930 mb for Hurricane Floyd of 1999. Katrina's unusually low winds were primarily due to the fact that Katrina was a huge storm--the change of pressure from outside the storm to inside the storm happened over a large distance. It's the pressure gradient--the change of pressure with distance--that drives winds, not the pressure itself.

Death Toll
The official death toll so far is 1336, with 1090 of those victims in Louisiana and 228 in Mississippi. This makes Katrina at least the fifth deadliest U.S. hurricane of all time. The death toll could go much higher, making Katrina the third deadliest. Over 4,000 people are still listed as missing. Most of these missing people are probably alive and well, according to Kym Pasqualini, CEO of National Center for Missing Adults. However, she indicates that 1,300 of the missing from the most heavily damaged areas of New Orleans are a matter of great concern, and many of these people may have died in the storm.

Damage
The report quotes a preliminary figure of $75 billion in damage for Katrina, a number used by the American Insurance Services Group (AISG). This would make Katrina, by a least a factor of two, the costliest hurricane ever. A recent estimate by the world's largest re-insurance company, the Swiss Munich Re Foundation, put Katrina's total damage closer to $125 billion.

Forecast accuracy
NHC gives themselves high marks for forecast accuracy for the 2 1/2 days prior to Katrina's landfall. Indeed, their landfall location forecasts had errors more than a factor of two better than average. These exceptionally accurate forecasts likely saved hundreds of lives. On the other hand, NHC intensity forecasts for Katrina were up to a factor of two worse than average, and perhaps more lives could have been saved had these intensity forecasts been better.

Jeff Masters
katrina surge
katrina surge
1st. Baptist Church Gulfport, MS
Katrina Damage at the 17th St Levee Break
Katrina Damage at the 17th St Levee Break
Hurricane Katrina Search and Rescue
Hurricane Katrina Search and Rescue
I work for Louisiana Wildlife and Fisheries. We are in search and rescue mode. Storm damaged and flooded house.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

They already came out with this Information????
I talked to David Millar of the NHC 2 days ago and he said nothing would be coming out until at least Jan. 15ish.......
Snowman, join some of your fellow bloggers in emailing the NHC to voice your concern over this downgrade if you disagree with it. :)
Cat 3 my ass...145 at first landfall in LA...135 at second landfall in MS...last time I checked, those were Category 4 winds...unless the NHC has changed the Saffir-Simpson scale without telling us!
TampaSteve, they lowered the winds to 125 MPH at first landfall and 120 MPH at second landfall.
Sorry, but 120 MPH and 28-30 foot surge doesn't add up...something ain't right there!
To me, what this shows is the absurdity of the "category" system, giving a one-number description of storms based solely on one factor, wind speed.
TampaSteve and rwdobson, please email the NHC with your concerns! Be polite but firm!
rwdobson: While some of the general public might find it confusing, maybe the NHC should have three category #'s for each storm, one for winds, one for central pressure, and one for surge.
TampaSteve, read my blog.
"Officially"...I think Katrina made landfall at Grand Isle, LA. Looking at the radar loop, the west wall of the eye passed directly over what used to be our fishing camp, there....emphasize "used to be".

All that remaints are two piling remnants. There were quite a few supporting the camp about six feet above ground.....as they've done since 1953.

Oh well...What's done is done. Life goes on. I wish that sentiment could spread through the rest of LA.
11. TBA
Whats the point of getting upset if a storm is classified as a category 3 or category 4 in the end, when the shaffir-simpson is totally inadequate to describe the damage from a hurricane.

Hurricanes take time to wind down, and a cat 5 that changes to a 3 in twelve hours is going to cause alot more damage, than a category three that has been steady state before landfall for several days.

What this controversy will do, is give a voice for change, to rate a Hurricane based on many factors, not just the windspeed.

After all wind does not kill by itself, its those flying toaster's or that 28 foot storn surge, when you don't have a surf board, that really gets you :)
I'm watching Fox News, and the NHC's downgrading of Katrina is now one of their big stories coming up next...great...now that it's on the news, the NHC will be far more reluctant to change their position.
TBA: Yup...the winds get all the press, but it's the surge and inland flooding that kill the vast majority of people in a hurricane. Remember, water is 800 times denser than air...we all saw what happened in Biloxi and Pass Christian.
It seems to me the 28-30 ft storm surge doesnt't necessarily
have to correlate with current wind speeds. So the storm surge can build up and maintain that height as the hurricane moves ashore even though the wind speeds drop off.

I'm sick and tired of the NHC trying to minimize these storms...Katrina was only a three, next it will be Wilma as only a one...
arcturus: That doesn't explain Katrina's huge discrepancy between wind speed and surge height in light of comparable landfalling hurricanes. For example, let's look at Ivan...it was a large and powerful Cape Verde Cat 5 that had record-breaking wave heights, and it struck Gulf Shores and Pensacola as a 130 MPH Cat 3...it had surge of 15-18 feet...I want the NHC to explain to us how a Cat 3 Katrina, which had less of a run over water than Ivan, carried a surge almost twice the height of Ivan into the Gulf Coast with winds roughly equal to those of Ivan at landfall.

Sorry, NHC...it doesn't add up...
Jeff, they *did* talk about the surge!

The massive storm surge produced by Katrina, even though it had weakened from
Category 5 intensity the previous day to Category 3 at landfall in Louisiana, can be generally
explained by the huge size of the storm. Katrina had on 29 August a large (about 25-30 n mi)
radius of maximum winds and a very wide swath of hurricane force winds that extended at least
75 n mi to the east from the center. Even though Hurricane Camille (1969) was more intense
than Katrina at landfall while following a similar track, Camille was far more compact and
produced comparably high storm surge values along a much narrower swath. Also, Katrina had
already generated large northward-propagating swells, leading to substantial wave setup along
the northern Gulf coast, when it was at Category 4 and 5 strength during the 24 hours or so
before landfall. In fact, buoy 42040, operated by the National Data Buoy Center (NDBC) and
located about 64 n mi south of Dauphin Island, Alabama, reported a significant wave height
(defined as the average of the one-third highest waves) of 30 feet as early as 0000 UTC 29
August. This buoy later measured a peak significant wave height of 55 feet at 1100 UTC that
matches the largest significant wave height ever measured by a NDBC buoy. Overall, Katrinas
very high water levels are attributable to a large Category 3 hurricanes storm surge being
enhanced by waves generated not long before by a Category 5 strength storm.
"That doesn't explain Katrina's huge discrepancy between wind speed and surge height in light of comparable landfalling hurricanes. For example, let's look at Ivan...it was a large and powerful Cape Verde Cat 5 that had record-breaking wave heights, and it struck Gulf Shores and Pensacola as a 130 MPH Cat 3...it had surge of 15-18 feet...I want the NHC to explain to us how a Cat 3 Katrina, which had less of a run over water than Ivan, carried a surge almost twice the height of Ivan into the Gulf Coast with winds roughly equal to those of Ivan at landfall."

TampaSteve, I would think the difference is obvious... Yes, Ivan had a longer run, and yes, it was at one time also a Category Five. However, I for one wouldn't call Ivan a "comparable" hurricane. Ivan weakened MUCH farther from landfall than Katrina did. Ivan lost C5 strength TWO DAYS before landfall, while Katrina lost it about half a day before. Ivan's storm surge had something like four times as long to weaken as compared to Katrina's. The fact that water's density allows it to maintain momentum so much longer than air does explains the discrepancy, or at least it seems like a logical explanation to me. Katrina's winds dropped rapidly, but the surge, which had already built up strength, didn't have a lot of time to weaken before landfall like Ivan's surge did.
Hey everyone,

I just completed my blog discussing whether Atlantic hurricane frequency is a result of global warming or simply the natural variability of climate change.

I add initially completed it a couple hours ago before I lost more than half of it after I had posted my thank you to all who read it. When I hit the update button, more than half of what I had written was gone! More importantly, the large portion that I lost was concerning the most important details on my discussion. As a result, I simply added a portion fropm another article on the all important AMO cycle and then wrote another conclusion about my personal thoughts on this controversial subject.

In short, please feel free to read my latest blog.:)

Thanks,
Tony


Good afternoon everyone

toroca, I want the NHC to explain to me how a category 5 hurricane like Ivan (which was a category 5 at three points in its lifetime, and spent nearly than 60 hours at category 5 strength, of which 36 hours of that came within 2 days of landfall) with almost exactly the same radius of maximum winds and hurricane force wind radius, how on earth it could only produce a storm surge of 10-15 feet when Katrina (which was only a category 5 for 18 hours and still weakened below category 5 strength 6 hours before landfall) was of no bigger size than Ivan, could produce a 23-28 foot storm surge at both landfalls. It seems to me that they really don't have a plausible explanation for the extremely low barometric pressure and the massive storm surge for Katrina.
All that matters here is the Gulf of Mexico. The waves and surge generated by Ivan over the Caribbean are irrelevant as they can't really travel across Cuba. Over the gulf, Katrina and Ivan traveled about the same distance. As was stated above, while Ivan moved across the gulf as a large storm hovering around 930 mb and weakening to mid 940s at landfall, Katrina was a huge storm, the king of storms, reaching 902 mb not far offshore and weakened to 920 mb at landfall. Both storms were nasty, but there is still an obvious gap in the size and strength of the two. I suppose it is also possible the continental shelf and coastline where Katrina hit is even slightly more prone to higher surge than the Florida panhandle is. I don't know that for sure, though.
Unfortunately, I don't have time to thoroughly share my thoughts regarding the post storm report from the NHC on hurricane Katrina. However, I will simply copy and paste a couple of posts that I made in Dr. Masters blog yesterday that will give you all an idea of my sentiments about it in case you didn't get a chance to read them.:)

Posted By: hurricanechaser at 10:16 PM GMT on December 20, 2005.

To be more specific..I don't think it matters to those in its direct path if the NHC says they only received a category three strike when they lost their loved ones and homes to a large category four. In other words, they can say she was a landfalling category one storm and it still wouldn't make it true. These residents who bore the absolute brunt of Katrina got hammered by a landfaling category four and writing a report saying otherwise can't change that reality. However, I think it's more of an injustice to these who did receive those sustained category four conditions for the official record to say otherwise. If you are going to err in such instances, I think it's best to go the other way.

Just think about it, we now have Katrina making landfall as a 920 mb category three with 125 mph sustained winds that will go down in the official records as hurricane Wilmas landfalling 125 mph winds when her lowest presure was 950 mb at landfall. That is a full 30 mb difference. Naturally, I am aware of the pressure gradient that creates such winds, but, I find it hard to reconcile a 920 mb presure with a 125 mph moderate category three storm.

The Missisppi landfall comes in at a 120 mph 928 mb hurricane that produces a 27 to 30 foot storm surge. Now that definately sounds logical. I read the NHC explanation for this huge surge and it was very unconvincing to put it mildly. The suggestion was that this is typical of a large category three hurricane that was a category five less than 24 hours prior to landfall which created a large wave setup. It is important to realize that the storm surge is the level of water rise above normal sea levels that doesn't consider wave setup nor their heights. That's why the look for still water marks on buildings rather than the highest water marks which are caused by the wave action. On the other hand, I by no means want to denegrate the catastrophic consequences that such wave action has caused to life and property and will do so again in the future. However, the historical record has to be accurate and that explanation doesn't hold water in my opinion (pun intended).

I agree completely chaser. Everything you wrote is true. I cannot stand it anymore. Every time I hear or read something about this downgrade it makes me sick. If anyone wants to read my views (which is actually only about 1/4 of my upcoming blog entry on the subject) then they can go back to yesterday at 9:13PM EST or 2:13AM GMT.
Posted By: hurricanechaser at 9:57 PM GMT on December 20, 2005.

THIS IS ABOUT THE FACT THAT THE NHC REPORT MENTIONS THAT A PORTION OF SE La. POSSIBLY RECEIVED CATEGORY FOUR SUSTAINED WINDS.

I agree that both TBA and yourself make excellent points and I couldn't agree more. If a location gets category four sustained winds as noted in the report, how can they say that that area only received a landfalling category three strike. Both Hurricane Emily in 1993 as well as Alex last season brought their respective NW eyewalls ashore along the N.C. Outer Banks and both are considered landfalls. For Emily, she is listed as a major hurricane strike when her maximum intensity was 115 mph and those winds never reached the coast. For alex, they took the estimated sustained winds that most likely occured and listed this 100 mph category two hurricane at the time as a 80 mph category one landfall. My problem is with such inconsistency. Based on these two examples and the NHC report for Katrina stating that it's likely that a small area of the extreme SE La. coast received sustained category four conditions that there should be no reason that she isn't listed as a category four landfalling hurricane.
HERE IS MY LAST POST YESTERDAY THAT SUMMARIZES MY FEELINGS ABOUT THE DOWNGRADE.

Posted By: hurricanechaser at 1:08 AM GMT on December 21, 2005.

Hey everyone,

I thought that I would post one more comment before I call it a night.

First of all, my sentiments of disappointment about Katrina being downgraded is the fact that I strongly believe that she wasn't categorized properly and for many of the victims that were afffected by this devastating storm feel that it is an insult that they lost everything they have to a large category four hurricane only for those who have no choice but to use subjectivity due to the lack of reliable wind data decide to downgrade the storm to a moderate category three.

In other words, I take it pesonally because I have family that lived through this storm and they are upset abnout it. Moreover, this is the prevailing sentiment from a few people I have talked to about this that I met while covering the storm myself. It is the equivalent to some of being told you only had gotten over the common cold when in fact you were fortunate to recover from pneumonia.

So is it better for the person to be told they have the common cold when they are battling pneumonia so that they will realize how much worse it could be if they get an even worse case of pneumonia. In other words, I have heard the argument that is shouldn't matter if the storm is clasified as a weaker storm because it will just help more people become aware of how truly dangerous a real category four could be. Although I understand the logic, I still disagree with the perspective as do those I have talked to that truly experienced the event themselves. Who am I or anyone else to tell those who lost their home or even worse a loved one that you should feel fortunate because it could've been much worse. For them, that is no consolation nor should it be.

No one truly disputes that Katrina was by no means the worst case scenario for the New Orleans area or anywhere else. On the other hand, it was the worst case scenario for more tan 1200 people who lost their lives and the loved ones who will forever mourn their loss. So I don't believe it's appropriate to talk about how only a little over a thousand lives were lost when it could've been thousands more. If one person loses their life as a result of any storm regardless of its intensity, we should show respect for that one life cut short because it was someones loved one or friend.

I hope that all of the aforementioned we help some understand why I feel so strongly about this downgrade that I personally feel is not justified by the incomplete and limited wind data, massive storm surge, and the incredible inland wind damage that I saw first hand. In short, I believe it is an injustice to those like my family and friends who lost so much as a result of this storm for the NHC to downgrade this storm a full category when it came down to a subjective analysis when it would've been best to leave it the same than make ill advised changes.
Now is the time to start changing the definition of "landfall". Why should a landfall be when the center of the eye feature hits the coast? That center is where the calm winds are. Landfall should be defined as when the outer edge of the radius of maximum winds hits the coast (or in essence, the point of landfall of the EYEWALL). Then, they would actually do justice to storms like Katrina, Alex and Ophelia. I find it mocking and totally pathetic that the NHC can mention that portions of southeastern LA probably recieved category 4 sustained winds and then record Katrina's landfall intensity at category 3 strength. Furthermore, you could make a case for landfall intensity being the maximum sustained winds observed anywhere at anytime while the inner core of the storm is crossing the coast. Because I can't really believe it when the NHC counts the MS landfall as a weak category 3 when Poplarville records a 134mph wind gust BEFORE INSTRUMENT FAILURE AND IT IS 50 MILES INLAND!!! AND THE SUPPOSED TIME WHEN THAT GUST WAS MEASURED THE NORTHEAST QUADRANT OF THE EYEWALL HADN'T EVEN REACHED POPLARVILLE. Amazing what people in power can do...
Hey Rich (Atmos),

It's great to see you again and I have thoroughly enjoyed reading your posts lately even though I haven't had much time to post myself.

I hope everyone has a great day and I might write a blog as to why I personally believe the downgrade of Katrina is inappropriate meteorologically speaking.

I just completed one about Global warming with a second one planned discussing the real catastrophy that we should be focusing on rather than any theoretical correlation between human induced global warming and hurricane activity.

On the other hand, I will wait to see what those like Rich (Atmos) writes in his blog first which I suspect will cover any issues I would include in my blog on the subject.:)
One last comment before I go. Rich,

You just summarized my feelings very well.:)

I hope everyone has a great day.:)
Great to see you too Tony. Yes I will try to finish my entry by this evening as it is extremely long (even longer than the email I sent the NHC last night LOL).

I will be focusing on writing my entry now so I won't post until later. In the meantime I hope everyone here has a great afternoon and I will talk to you later.

Rich (Atmos)
Well, well...What convenient timing by the NHC to publish their final report on Katrina, 4 days before Christmas when many of us are quite busy w/ the holidays to have the time to discuss this important topic. My time here is short now, but I'll have some points to make in the near future as I just downloaded the 42 page report.

Thanks to Tornadoty, 'Canechaser, and Atmosweather for giving us a heads-up last nite on the subject. I appreciated each of your responses, and feel largely in agreement. Unfortunately, I doubt there is anything we can prove to change the NHC's analysis, but we can sure question some of the methodology and discrepancies toward the validity of the data...or their failure in accounting for lost surface observations that encountered that tremendous eyewall, particularly the eastern half.

Okay, not gonna rant too much and, yes Katrina weakened before LA landfall as she encountered dry air entraining, increased shear and was apparently beginning another EWRC - another factor contributing to expanding a huge windfield to more monstrous proportions. I can accept a reduction from operational wind intensity of 145-150 mph downwards, although the 135 range would seem more plausible. A full 20+ mph reduction in that time frame indicates an error somewhere in the methodology, whether from aircraft recon's sampling or HRD's assessment ability.

Yes, Safir-Simpson's wind-only scale often fails to give the average person a reasonable view of storm damage potential. A number of you have worked on detailed scales to improve this situation by including surge height and wind radius. But, and I have said this before...to help simplify those two factors all you need to include is what can be found on the Vortex Data Message, section M. - Eye Diameter...it really explains clearly the differences in wind field breadth and surge height/width within storms of the same category, to my way of thinking.

Jeff Masters...sure is nice to see NHC patting themselves on the back for their forecast accuracy 2.5 days out. But there is a good reason Max Mayfield was desperately calling the governor, the mayor, and everyone in SELA by late Friday...just go back into the graphics archive on Katrina for that day (and previously). Quite a shift wasn't it? And curiously the 2 pm advisory graphic is missing...someone was very busy doing a redraw.

Catch y'all later. Everyone have good day. Gone fishin'.

Oy, what's with all this paranoia? What motive could the NHC have for lying about the category of Katrina at landfall?
Hey Ays,

That's not a difficult question to answer in reality. If you all can remember the infamous Times Sentinental article that wrote extensively about a possible downgrade of Hurricane Katrina to a 115 mph category three at Buras and a 95 mph category one for the Mississippi landfall as suggested by Dr. Mark Powell with the HRD.

That article was filled with political overtones as it focused heavily on the political consequences of New Orleans and the Levee systems actually succombing to category one winds rather than category four winds as suggested operationally speaking. It is important to note that the NHC made mention of this in there report when they stated that that area ONLY saw category one or two conditions.

There were many such as Dr. Powell for example who wanted to downgrade her further but I believe the NHC wanted to take the middle ground so to speak and find other ways to explain Katrinas huge storm surge for example despite only having a category thre intensity by their estimation as well as still being able to note in their report that New Orleans and their levee system failed below category three conditions.

In short, there were most likely political reasons that distorted the obvious subjective analysis required here. Just notice how the NHC thanks many of those same HRD scientists for their contributions to the report.
Hey DocNDswamp,

It's nice seeing you again and yet another excellent post as usual.:)

I couldn't agree more with each of your individual asssments.:)

You are so welcome and thanks for the kind words.:)

After reading several of the above posts a newspaper headline popped into my head...

HURRICANE CENTER DOWNGRADES KATRINA TO A CAT 3 AT LANDFALL, KILLING ANOTHER 2000 PEOPLE IN THE PROCESS

I have some comments to make. First, the current category system needs to be scrapped. The political BS involved with the current system is becoming unbearable, not to mention the science. Second, I find many of the above posts beyond ridiculous. Downgrading the WIND speed at the tip of the Mississippi delta is an injustice to people who lost family, friends, and belongings? You have got to be kidding me. I'm sorry, but that is one of the most absurd things I have read in a while. And what the heck does downgrading the wind at the tip of the Mississippi river delta have to do with observed "incredible inland wind damage" up in the state of Mississippi? I'm pretty sure a couple hours of 100 mph to 120 mph wind will cause some incredible inland wind damage. In addition, the NHC report keeps Katrina as a cat 3 when it hit coastal Mississippi, which means they changed almost nothing from the data given to the public back when the storm hit. So Katrina has ALWAYS been considered a cat 3 when it trashed the highly populated coastline. For 99% of the storm victims cat 4 never applied to your area in the first place. Many of you are flat out turning a molehill into Mt. Everest.
The significance of the title of this blog, "Katrina officially downgraded to a category three" simply means that the NHC now is OFFICIALLY wrong.:)

YOu have to find it kinda ironic that they decide to ugrade hurricane Andrew 10 years later by 20 mph for landfall where they received the brunt of the storm. Yet, they don't seem to have the same motiviation and perspective when evaluating storms that didn't impact them directly. I agree with their estimate of 80 mph for the Fl. landfall which occured in their own backyard. Regardless, if there was any real debate about that intensity, you can rest assured it wouldn't have been revised downward.

With regard to the upgrading of Andrew and downgrading of Katrina, there is a very simple explanation. The difference is huge between a storm that is weakening or going through an eyewall replacement cycle at landfall and a storm that is rapidly strengthening at landfall. Various factors make it so we see very few of the latter. Andrew happened to be one. Andrew's pressure was falling quickly, and the eyewall structure and convection intensity peaked as the eye moved inland. Contrast that with Katrina where the pressure was rising and the eyewall structure and convection intensity were waning as the eye moved inland. There is a clear difference in radar presentation at landfall between Andrew and Katrina. The inner core structure means everything in determining how much of a storm's wind gets transfered all the way down to the surface. That is why I don't like how the NHC uses the 10% reduction rule almost without exception. Back in 1992 they I believe they used a 20% reduction, but the rapid strengthening and intense inner core apparently caused an underestimation of the amount of wind reaching the surface. Largely because of Andrew they now use the 10% rule. However, it is my opinion that is most cases the NHC now overestimates the wind reaching the surface with landfalling hurricanes, especially with weakening storms.
Hey Hawk,

I'm glad you decided to invoke portions of my posts and chose to belitle an opinion that you don't understand, therefore, I will be more than happy to reply in detail.:)

HERE'S YOUR QUOTE,

Second, I find many of the above posts beyond ridiculous. Downgrading the WIND speed at the tip of the Mississippi delta is an injustice to people who lost family, friends, and belongings? You have got to be kidding me. I'm sorry, but that is one of the most absurd things I have read in a while. And what the heck does downgrading the wind at the tip of the Mississippi river delta have to do with observed "incredible inland wind damage" up in the state of Mississippi?

I will try to make it a little easier for you to comprehend. First of all, the intensity of Katrina at landfall has alot to do with her eventual intensdioty throughout its future course thereafter. Thus, if she was ony a landfalling 125 mph category three at Buras and 120 mph category three at Mississippi landfall which the NHC says was rapidly weakening, the wind gusts and damage more than 100 miles inland is very relevent in helping to determine her true intensity way back at the coastal areas.

Let's consider the stats for example...the NHC says the highest observed wind gust if I remember correctly was only about 115 mph or so along the coastlines. In contrast, its quite amazing how a rapidly weakening 120 mph hurricane produced wind gusts over 135 mph a full 50 miles inland prior to instrument failure. Likewise, please with your obvious infinate wisdom and meteorological background I'm sure, so please explain to me how this rapidly weakening minimal category three at the coast created wind gusts of 102 mph 65 miles inland, 114 mph 85 miles inland, and 111 mph a full 120 miles inland all prior to instrument failure. I must add that I was 0.1 miles from the location that recorded the 102 mph gust at 1 pm CDT and I have recorded evidence that the winds increased dramatically thereafter for a full 30 minutes after that time. It's also important to note that the NWS in Jackson, MS> states that damage of even F3 was observed in many inland areas well away from the surge and even damage equivalent to F1 up to 200 miles inland. Just look up the wind intensity required to fo that type of damage.

Therefore, I believe it is quite obvious why the "incredible inland wind damage" plays an important role in determining Katrinas true landfalling intensity since few anemometers actually recorded winds in the NE eyewall at landfall and were able to survive prior to the worst conditions getting there.

The fact you say that this comment is absurd shows how little you understand about estimating intensity of storms which is something I have done for the NWS here in Wilmington a few years ago and am not simply playing a meteorologist on the blogs.

And for you to denegrate those who feel that this downgrade is an injustice to them who lost loved ones for example as well as all their worldly possessions is one of the most "absurd" to use your terminology I have ever read myself. Who are you to tell these people how to feel? These are direct quotes from friends that I talked to last night after the report came out.

I will give you one of their quotes...hopefuly it won't be too deep for you to understand...

they said, "it is like your doctor writing in your medical record that you only had the common cold when in reality you had recovered from a severe case of pneumonia."

Even though the consequences are the same, it is still important to them to have the historical record to accurately report the truth as it would be in the aforementioned analogy.

To clarify your apparent confusion when you state that you don't understand how a small reduction for the Mississippi landfall has to do with it when it still came ashore as a category three. Here it is simple and direct for you...

IT WASN'T A CATEGORY THREE AT MISSISSIPPI LANDFALL.

I would argue that it was a 135 mph category four and a 145 mph category four for Buras landfall.

So, there's a big difference in my opinion from a 120 mph weak category three to a 135 mph category four.
Hawk,
I like how you want to try and disputes all of my comments..lol

I didn't say that I disagreed with Andrews official adjustment in intensity. Please read it as it was written without skewing the obvious intent of my comments.

Moreover, I find it ironic that you chose to focus on "the incredible wind damage" from that lengthy post and excluded the other rationals I mentioned that suggest Katrina wasn't a category three at Buras landfall such as the massive surge, incomplete wind data, and extraordinarily low barometric pressure. Please don't try to educate me on eye wall replacement cycles, structure, etc. So far, you haven't told me anything I hadn't known for the past 10 years.
For those of you who have not yet, PLEASE send your gripes to the NHC. At least we can put thoughts in their minds and make them answer tough questions that are hard to explain in the current report.

Also, Ivan was a large 3 and had a maximum wave height of 131 ft, the tallest non-seismic (non-tsunami) wave in history. It did not have a 28 ft storm surge. It's not adding up. Period. End of discussion.
Hawk...good to hear from ya.
But c'mon man, I believe what all of us are asking for is accuracy and consistency from the NHC. As I said earlier, a full 20 mph reduction indicates a serious flaw occurred somewhere. You're right though..few realize how powerful 100 mph winds are and can easily assume damage was caused by much stronger wind speeds.

But for another example; Remember the night you and I and a handful of others tracked Beta into Nicaragua? NHC was way slow in correcting to that SW movement, as well as taking over 4 hours before upgrading Beta to Cat 3...after it had obviously already gone past peak. That 1 am advisory was a joke and Richard Knabb at 4 am essentially said the same.
All I'm saying...some consistency is lacking.

OK, gotta run. Take care, Merry Christmas all.
Hawk,

If you have issues with my comments, you should also notice that I am by no means alone in my opinions.

Here is a fact that isn't left to subjectivity by you, NHC, or myself for that matter.

The TRUTH will always remain the TRUTH regardless of anyones personal opinion of it.

There is no way to know for certain exactly how strong hurricane Katrina was at landfall but however intense she was is precisely the truth. The truth may just contradict your opinion and those expressed in the NHC report.

In other words, if I ask you what color is my white car and you say its red and another says its green, it won't change the fact I still have a white car.
Hawk,

I am one of the few who does know what a 100 mph wind can do as well as a 130 mph one as well because I have intercepted these extraordinary winds. So, once again, I am sorry that you can't enlighten me with such knowledge.
I am going to keep this post short. I am shocked that Katrina was downgraded to a cat 3. Looking at thoes pictures that looks more like a weak 4.Someone mentioned that they diddnt talk about storm surge that is something that is very important that needs to be looked at more.
what up all look at the photo they look like more like a cat 4 too me then a cat 3

whats all go lol on the nhc or start calling them up

and say mske this a cat 4 at land fall 125B is not a cat 3 storm at all 125B or what ever it is look more like a cat 4 or cat 5 to me
AYS,

Please read my comment regarding the surge explanation in their report. It was a very poor explanation that isn't correct to begin with. The wave set up from it being a category five has nothing to do with it producing a 27 to 30 foot storm surge.

HERES MY PREVIOUS COMMENT REGARDING THEIR SURGE EXPLANATION.


The Missisppi landfall comes in at a 120 mph 928 mb hurricane that produces a 27 to 30 foot storm surge. Now that definately sounds logical. I read the NHC explanation for this huge surge and it was very unconvincing to put it mildly. The suggestion was that this is typical of a large category three hurricane that was a category five less than 24 hours prior to landfall which created a large wave setup. It is important to realize that the storm surge is the level of water rise above normal sea levels that doesn't consider wave setup nor their heights. That's why the look for still water marks on buildings rather than the highest water marks which are caused by the wave action. On the other hand, I by no means want to denegrate the catastrophic consequences that such wave action has caused to life and property and will do so again in the future. However, the historical record has to be accurate and that explanation doesn't hold water in my opinion (pun intended).



The NHC did the right thing.
Posted By: thebige at 9:33 PM GMT on December 21, 2005.
The NHC did the right thing.


how can you say that?
Thebige, explain your reasoning.
It is so interesting to me how it appears to be that the many of the weather opinions, whether it be about Global warming or this downgrade of hurricane Katrinas intensity, seems to be influenced by ones personal political beliefs.

I am not suggesting that this is the case for everyone. However, I can't help but notice that many of the same people who take exception to people critisizing this downgrade have posted other times contradicting the personal views of the same people, most notably regarding global warming which certainly seems to be divided along political affiliations.

Naturally, I could be absolutely wrong, it is simply a possible observation.:)

Regardless, everyone is entitled to their own personal opinions. I simply ask that we respectfully disagree and not make personal attacks on others with dissparaging comments such as some that have already been posted earlier.
From Dr. Jeff Masters:
"Note, however, that Hurricane Camille of 1969 did not weaken when it pounded Mississippi as a Category 5 hurricane; perhaps it's small size protected it from substantial land interaction and entrainment of dry air."

Perhaps this is why compact-size Charley was able to not only maintain its strength, but actually strengthen just before landfall. Then again though, Dennis was just about as small, but it lost strength before landfall...so I guess it depends on the storm. It would be interesting to do a study on hurricanes such as Camille and Charley on this subject, and especially Charley since it did just the opposite of what most hurricanes do before landfall. Oh! Another one just came to mind...Andrew did the same thing, and it too was a compact storm. Maybe there's some kind of a connection here? Anyone care to take a crack at that?
Hey thebige,

I respect your right to share your opinion.:)

here is my own.:)

The NHC did the wrong thing.
Quakeman, Dennis began an eyewall replacement cycle about 5 hours before it made landfall. Otherwise, it would have been a category 4.
Hey Tony (hurricanechaser), please stick around a little bit. I am finishing my letter to the NHC, and I would like for an experienced meteorologist (you) to make sure I am not a complete lunatic in the letter.
Hey guys

I have started my blog entry and you are welcome to comment on it and suggest anything else on the subject

Torn, I would like to read your letter, so you can send it to me.

Rich (Atmos)
The massive storm surge produced by Katrina, even though it had weakened from
Category 5 intensity the previous day to Category 3 at landfall in Louisiana, can be generally
explained by the huge size of the storm.That's why it seems in pictures that is was a Cat 4 ,But really it was a Cat 3.
thebige

So why did Ivan or Wilma (that both had almost exactly the same radius of hurricane force winds as Katrina) only produce a 15 foot storm surge at maximum?
Here is my letter guys. It is 415 words, short, straight, and to the point. Please critique it.




Wednesday, December 21, 2005




To whom it may concern:

I have read the National Hurricane Center report on Hurricane Katrina, issued Tuesday, December 20th, 2005. I have a couple nagging questions that I feel must be answered concerning Hurricane Katrina.

1. In section b, paragraph nine, sentences ten and eleven, it is mentioned that sustained Category 4 winds of 135 MPH (115 kt) may have reached the southeastern coast of Louisiana . If this did occur, would Katrina not count as a Category 4 strike on Louisiana?

2. I understand how the expansion of the pressure field could lower the winds in the hurricane. However, I was looking at the advisories and report on Katrina and comparing them to Hurricane Ivan of last year and I noticed a few things that puzzled me:

a. When Ivan made landfall on the Alabama Gulf Coast last year, it had winds of 120 MPH, a pressure of 946 mb, and a maximum hurricane-force wind radius of 105 miles. According to the Katrina report, the winds at landfall were 125 MPH, the pressure was an incredible 920 mb, and the wind field was 120 miles at the Buras, LA, landfall. Was the fifteen-mile difference in the radius of the wind field really enough to counteract the huge 26 mb difference in pressure between the two hurricanes and bring the sustained landfall winds so close together? I understand the effect that pressures in the surrounding environment of a hurricane affect the wind speeds in a hurricane, but were the environments surrounding each hurricane different enough to cause this large difference in pressure and wind relationships in the absence of a large difference in the wind fields?

b. The authors of the report explain on page 9 of the report that the huge surge of Katrinas was caused by a large Category 3s storm surge and the large wave action of up to 50 feet prior to landfall. The surge of Katrina, according to the report, is at least 28 feet. Hurricane Ivan produced an unofficial wave height of 131 feet over the Gulf, with numerous reports of 50-60 foot-tall waves. I know that the topography near the Mouth of the Mississippi River is a more surge-vulnerable and surge-enhancing area, but why is there a 12 feet+ difference in surge if Katrinas was enhanced by wave action? Wouldnt Ivans be higher if the wave action played a large role?

Thank you for taking time to answer these questions.



Sincerely,
Anthony Lyza
Hey quakeman,

I have a good observation that may serve to be a good explanation as well.

First of all, there has only been one category five recorded at or above 30 degrees latitude which is Hurricane Camille anywhere in the Atlantic Basin.

Secondly, hurricane Andrew and the great Labor day hurricane were even smaller compact hurricanes than even Camille who were both intensifying as they struck the U.S. coastlines. Hurricane Charley is an excellent example of a strengthening category four. Each one of these hurricanes remained below 27 degrees latitude where there is warmer waters and generally less dry air entrainment closer to the more tropical areas of the Atlantic Basin.

Thirdly, you mentioned the size component of the storm such as the three of the four I referenced above. It is important to realize that smaller hurricanes are able to intensify more rapidly as well as be far susceptable to weakening if shear is present in contrast to larger storms. You already mentioned Dennis as an example of a weakening smaller storm. In contrast, Dennis was a rapidly strengthening category four before it closed in on the Northern Gulf Coast as did the very compact Hurricane Lilt that went from a 145 mph category four to a 90 mph category one in less than 18 hours in 2002 before hitting the La. coastal areas.

Fourthly, there are many examples of the opposite being true for large storms which were strenthening as they came ashore even some above 30 degrees latitude such as category four hurricanes Hugo in 1989, Hazel in 1954, Audrey in 1957, Great Galveston hurricane in 1900, Hurricane Donna in 1960 and strong category three storms such as Fredric in 1979 just to name a few off the top of my head.

In summary, that theory is disputed by the historical record as recent as the 2002 season with compact hurricane LIli and Dennis as you already mentioned.
Very well-written torn. Good questions as well. I said basically the same things and only added something about the 134 mph wind gust in Poplarville, yet I wrote them a 1410 word book!!!
Every storm is different.
Hey Tony,

I want to personally commend both you and Rich on excellent letters to the NHC. I was going to write my own as well. But it appears you two have already addressed my specific concerns fairly well.

I should also mention that I sent a very lenghthy email to the NHC awhile back (anyone surprised by that?..lol) after the HRD was pushing for far greater reductions in intensity.
Hey Tony, wasn't Isabel close to 30 North when it was a category 5?
I'm sorry thebige, but "every storm is different" doesn't explain anything. That may be true, but how on earth can two hurricanes with similar properties carry such different results? Katrina's surge had nothing to do with its size, it had to do with its intensity. That is why you can't have a category 3 storm holding a U.S. record 24-28 foot surge. It's not feasible.
Hey thebige,

That was precisely my point and the atmospheric conditions are very susceptable to change which is why its difficult for category five storms tto maintain that intensity for long periods of time not to mention the inner storm dynamic that come into play such as eyewall replacement cycles.

Hurricane Isabel:

09 GMT 09/14/03 23.3N 65.2W 160 938 Category 5 Hurricane

That was the highest latitude Isabel was at before it weakened below category 5 strength
That last post was concerning hurricane Katrina whatsoever but was a summarization of my explanation to quakeman.

Thats a very important distiction I need to make.
Thanks Rich..I didn't remember te latitude off hand and I was getting ready to look at the NHC advisory archives myself. Thanks for geting that for both me and Tony.:)
Thanks guys!

And Tony, you should send a letter. You are a professional meteorologist with (correct me if I'm wrong) a DEGREE and your reenforceing of our points can only help!
I don't know every thing.I'm only 13.
Oh well, saw it on tv last night and on this blog today..Wonder what Wilma will be downgraded to for Broward County??? a Tropical Storm??? I mean, it had to come across the Everglades before hitting us...eventhough the Everglades is not capable of slowing down any hurricane, actually Irene got strong if I remember correctly...

I can just imagine what will happen in Broward if Wilma is downgraded even more than was was already... No lights, no power, no phones, blocked roads, homes destroyed, business destroyed..all by wind...not a drop of storm surge did this...just venting.....
Sorry. I knew Isabel was a bit north. I was thinking too far north.
Wow..I am so sleep deprived..I can't even correct my correctionms..lol:)

That last post was (NOT) concerning hurricane Katrina whatsoever but was a summarization of my explanation to quakeman.
Wow, the bige. I certainly didn't know you were 13 and I have to say you know a lot for your age
No problem torn. No one can be expected remember such a statistic as that!
I agree Tony..I will also go ahead and write the letter and most likely will post it in my blog as well.:)

you each (Rich and Tony) did an excellent job with yours respectively.
Glancing at the comments it appears a lot of confusion about the downgrade to Cat 3. Actually NHC was generous; the data doesn't support sustained winds quite as strong as identified in the final report, but I think NHC made a reasonable choice.
Thanks:)
Thanks chaser. If you havent already then you should read my blog. Not finished by any stretch but some of my points are in there.
I read it squeak, but nothing really flies for me. Too many inconsistencies and points that do not make sense meteorologically.
You're kidding right, squeak?
That's What I thought Squeak.
Hey sqeak,

I respect your opinion...but I respectfuly disagree and suggest that the data supports a category four. Even the NHC states that it is likely that a portion of the SE La. coastline experienced sustained (not Gusts)category four winds. How can they then record her as a 125 mph category three?

This doesn't even consider the data of pressure, record storm surge of 28 feet (poor explanation for that in the report), and winds above 120 mph more than 120 miles inland all from a rapidly weakening category three storm at landfall on Mississippi coastline. These frequent powerful inland wind gusts and F2 and F3 wind damage is very relevant to the true intensity at landfall since the anemometers along the coastal areas were disabled well before experiencing Katrinas powerful eyewall.

Not to even mention the 135 mph wind gust some 50 miles inland at Popularville, MS. Thats pretty extreme that far inland for a rapidly weakening minimal category three.

These are just a few of numerous examples as to how I believe that the the DATA does support category four intensity despite the limited data that is indeed available.
I want to know how they got those cross-sections for the last diagram, and which way the radar points on the hurricane hunter. If it points down to the surface, can't they get wind velocities from that?
Hey guys just wanted to check in and say hello....One thing I wanted to say is that we only know about 25 percent of what makes a hurricane go. We are learning so much every year. Especially that we have so many specimens to dissect. Along with hurricanechaser, I had 5 hours of hurricane winds in Hurricane wilma......I was exhausted. You need several keys to bring everything together to have a cat 5, including a little bit of luck. You have varibles up and down the atmosphere. You have a spinning top called a hurricane that can bounce back and forth....with the winds stronger the higher you go up.

But the main thing that everyone needs to understand is that there is no set format for a hurricane. Each one has a different layout. There are no rules. Just consequences if you dont respect it.
Everyone have a good evening and merry christmas!......Hey hurricane chaser..........see ya!
Gonna take a break now. Got a lot of stuff to do. I will try and get back on this evening

If not, then I hope everyone has a great night.

Rich (Atmos)
Ok, chaser, here is my response...

I specifically said the angry attitude toward the NHC report was ridiculous and absurd. It was also no accident that I included the words "I'm sorry" at the beginning of the statement. I don't remember typing anything like, "chaser, himself, is a ridiculous and absurd idiot for thinking this way". I don't know you, I only know what I read in your post, and the attitude, specifically, of the post was in my opinion ridiculous and absurd, and that is still my opinion. You use the common cold vs pneumonia example, but a better example would be a doctor writing "moderately severe pneumonia" on your medical report instead of "severe pneumonia". It's not like the NHC has downgraded Katrina to a tropical storm at landfall. You seem to be the only one around here denegrating others. If you think your facts trounce some of what was written in my post then I'd love to read them. Heck, I might even *shock* at least partly agree with you. The added dose of condescension in each of your paragraphs doesn't help your argument. It is well and good that you have worked for the NWS and have experienced hurricanes. I have also spent much of my life analysing hurricanes so I am very knowledgeable, too. But that hardly means either of our hurricane analysis and intensity estimation skills are ironclad. The folks at the NHC should theoretically understand this stuff more than anyone, yet you obviously feel you have a strong reason to disagree with them.

I don't dispute any of your wind data. I had not heard of the "F3 wind damage" info, and 158+ mph does sound a bit high, but hell, if that's what the NWS office says occurred then I certainly won't dispute it. If there were in fact wind gusts that high my first thought is that the sustained wind estimate would be a bit higher than the 120 mph stated in the new report. That said, I would be interested in what the NHC has to say about the NWS report.

The NHC report talks about Katrina weakening rapidly as it approached land and then weakening rapidly as it moved inland across south and central MS. I suppose going from 902 mb to 928 mb before the mainland landfall qualifies as rapid weakening, but I remember that once the center moved inland the eye remained remarkably intact for a while and I believe there was a burst of deep convection around the eye as it approached the Poplarville(mentioned in NHC report) and Hattiesburg area. That convection could certainly have helped transport some of the higher wind to the surface well inland even as the pressure was rising steadily. Bottom line is that I am not endorsing the data behind the NHC downgrade nor am I blasting the science behind your disagreement with the NHC. These kinds of arguments unfold because of our extreme ineptness when it comes to placing durable and accurate instruments along the coast. It would be a shot in the arm if something could be done to aleviate this problem, but I'm definitely not counting on it. We'll probably still be squabbling about hurricane landfall wind speed 20 years from now.

Wow. Interesting debate guys. I think I used up all my argumentativeness last week, on sports blogs, debating Kentucky fans about whether Randolph Morris signed with an agent or not...

But anyway, I need to read the report before I can comment too much. I do know that government agencies routinely release controversial findings during holiday times, or on Fridays, and I think that probably happened here.

I think that the NHC is trying to protect its backside (save ass) by down-grading Katrina to a cat 3 trop cyclone. Maybe some insurance policies state, "We'll pay if the storm is a cat 4, and no, if it's a cat 3!" We'll ignore flooding in this instance also! The NHC is federally funded and when your funding may be in jeopardy, it's subject to manipulation! Remember
The White Star Line was found to be 'not guilty' of negligence after the 'Official Enquiry' concluded its deliberations into the sinking of the 'Titanic' with a loss of 1525 lives in 36 degree water. Why, insurance claims by the next-of-kin were or may not be paid if the cause of the sinking was an accident. But, the ship was doing 22 knots though a field of bergs on a moon less night when the North Atlantic was as calm as a 'mill pond'. Other ships had stopped for the night! The lookouts did not have binoculars! The White Star Line was seeking publicity wrt a fast crossing and favorable publicity sells tickets (and yields profit)!In other words, You are on your own!
Ah! The conspiracy theories hath begun with one that makes sense!
Hey Hawk,

I wish you would realize that the analogy that I have now posted twice that you have alluded to is not my own but a direct quote from a Mississippi resident who lost everything and had to move out of the state. So your critique of the quote isn't towards me and I can give you this persons email adress if you would like tyo tell him yourself how ridiculous and absurd his thoughts are. I stand by my pevious comments stating how those residents feel it is an injustice because I have two family members in La. as well as three friends that I talked to about this downgrade last night that I had met while I was down there.

Here is your direct quote once again..please tell me if your attitude is appropriate and not disrespectful...seems to me that I didn't attack anyone personally directly or indirectly until this post and I then added sarcasm in response which I agree was inappropriate on my par.

"Second, I find many of the above posts beyond ridiculous. Downgrading the WIND speed at the tip of the Mississippi delta is an injustice to people who lost family, friends, and belongings? You have got to be kidding me. I'm sorry, but that is one of the most absurd things I have read in a while. And what the heck does downgrading the wind at the tip of the Mississippi river delta have to do with observed "incredible inland wind damage" up in the state of Mississippi?"

I find it absurd to once again use your terminology to suggest that your use of the words, "I'm sorry" was no accident and somehow shows respect in your suceeding comments. Please a little honesty would be most appreciated. that use of I'm sorry is what we all use with sarcastic ovetones as noted by the words that followed that it was "one of the most absurd things you have ever read" and "you have got to be kidding me", and "what in the heck does "incredible inland wind damage", etc.

Who wouldn't objectively take issue with your attitude in psting those comments...how can you critisize my angry atitide as you stated, which is not how I feel at all...try frustrated for my friends and family and I did get angry wit your unnecessary rude and degrading comments in reference to a direct quote from someone who lost so much in the storm.

Please tell me who are you or I to question their feelings?

In your haste to take issue with my post, you have continued to overlook the fact that the injustice and the analogy are quotes from my friends and I respect their opinion..why can't you?

Please reread your post again for you must not remember what you initially said...because this comment contradicts your original post.

here' your comment from the second post contradicting the first above...

" specifically said the angry attitude toward the NHC report was ridiculous and absurd. It was also no accident that I included the words "I'm sorry" at the beginning of the statement."

Why can't some people be honest and try not to start arguments with others who have not said a word about them with rudeness and sarcasm?

Please read the Jackson Mississippi NWS report and feel free to take issue with their findings of F2 and F3 damage well inland away from the coast if you have a problem with me posting their findings.

And lastly...it is quite apparent by this comment that you jumped at the chance to engage me in an argument with your rude comments knowing I would respond accordingly. YOu wil never find an example in any blog where I have ever started an argument with anyone which still remains the case now.

"You seem to be the only one around here denegrating others."

Now, where in the heck to once again use your respectful terminology from your initial post get that absurd idea.

I am sure many will read these back and forth responses and say I am once again engaging in this ridiculous and childish behavior but I have to take issue with your desire to attack me personally..you didn't have to say "chaser"..we both knew you were talking about me with direct quotes from my post.

Honestly, I pray that you wil grow up and be a real man and stop looking for confrontation and try reading what was written before once again attacking me for something I quoted from others. Moreover, I am not contradicting anything I've said in my earlier posts which you can't say.

Let's try being a little more humble and honest can we.
Hey Hawk,

I respect your input and even agee with many of your points in your posts. However, I take exception with your attitude. Please go back and read all of my posts and please find one example of where I denegrated others as you put it. I did return the sarcasm in my response to your rude commentsin your initial post which was indeed wrong but I didn't precipitate this argument, you did.

The posts are there to reveal the truth..please reread them.:)
ok, one last post for the night... Hey Hawk,

I forgive you for your sarcasm and I certainly was very sarcastic and rude to you in return. I simply ask you to forgive me.

I simply want us to debate the science and respectfully disagree if we do.

I hope everyone has a great night.:)


Okay guys, calm down. There are so many good points you have made, it would be a shame to let it denegrate into a testosterone battle! I think that a few of you should compile a letter together and float it around WU, (with the disclaimer that it is only WU bloggers, not WU itself) for us to sign, as a sort of petition. I am sure that so many of us who depend on your expertise would gladly sign that the NHC would have to take notice. Just my opinion.
As for the "steady-state" example - if Katrina was a Category 3 about 8 hours from landfall and overnight strengthened to a Category 5 and made landfall as such, the damage and especially the death toll would have been far less, as the storm surge wouldn't have built up - the damage would be primarily from the 175 mph winds (mind you, it would still be in the tens of billions of dollars).

Looking at my estimates, I still think they overadjusted wind gust estimates (which were incomplete); I believe it was 140 mph at final landfall and 150 mph at Buras.
i got a good lighting storm comeing in

The 135 mph wind gust at Poplarville is even more dramatic considering that was on the LEFT side of the eyewall - it would have been more like 150 mph on the strongest side. I estimated that Katrina was still at least 120 mph AT THAT POINT.

The 120+ mph wind gust in Pascagoula - 60 miles from the eye and when the eye was already ashore - suggests that Katrina was still a Category 4 hurricane at Pearlington landfall, considering it wasn't even in the eyewall. That would have been when Katrina was about 10 miles inland, and I estimate that Katrina was 135 mph at that point. With slight weakening after landfall, I believe 140 mph was the real strength at the final landfall at the MS/LA border.

The Buras landfall is tougher to estimate - with no information to back it up, it could have been anywhere from 145-155 mph.
Code's got a good idea. Give me a few minutes, and I will set a petition up on my blog.
i got a good lighting storm comeing in
I have set up the Katrina petition.
Hey Code,

I totaly agree with ALL of your comments and that was an excellent idea you suggested.:)

Hey Crazy,

I find your last post to be an excellent post and one that is very compelling in stating that Katrina was indeed at least a minimal category four at Mississippi landfall.

Hey Tony,

Once again, I was very impressed with the contents of your letter to the NHC.:)

Hey David,

I hope you are doing well.:)


I would highly recommend everyone read Atmosweather (Rich) blog on this subject. He did a surberb job in my humble opinion!:)

Hey gjs,

I definately can see that as a legitimate possibilty regarding your theory as to why the NHC made the downgrade.

I had also suggested that politic overtones may have played arole in determing the true intensity when subjectivity had to come into play with such an incomplete wind data at landfall.

You actually made me think of another possibilty as I was reading Rich's excellent blog when he was discussing the NHC intensity estimates and how they commended themselves for the final intensity being right five days out. I can't help but wonder if that also played a role in their subjectivity which could've been skewed since their funding as you mentioned may very be dependent on their performance...just some thoughts.:)

I hope everyone has a great night and a very Merry Christmas if I don't have a chance to post again before then.:)

Your friend,
Tony
I signed it - based on my estimate, the 120 mph winds were at Poplarville, not at landfall, when adjusting for the side of the storm and the fact it was a gust (gusts on the right-front quadrant had to have been in the 150-160 mph range at that point).
hey hurricanechaser and ever one what up did any one get a e mail from the nhc yet
Crazy, if you don't mind, I need names for any petition that will go to the NHC.
Everyone please ignore my last comment.
While hurricanechaser's remarks stating that the downgrading of Katrina has upset many of the victims may sound silly to some people, I can testify from personal experience that those who have lost everything to a violent storm do indeed have a need to feel that their experience was a record-breaker. My former hometown of Wichita Falls, TX was devastated by a mile-wide tornado on April 10, 1979. The destruction was so total that Dr. Ted Fujita himself participated in the damage analysis. Although I personally witnessed at least two houses that had been swept completely clean off of their slabs, supposedly a marker for F5 damage, Fujita and Texas Tech University researchers decided that the damage could have been produced by "only" a strong F4, so that was the official rating assigned by the NWS. Many of the locals were angered by this decision and remain bitter to this day. Some people drove around for weeks in their battered, windowless cars with bumper stickers that said, "Our Tornado Was Worse Than Your Tornado!" (an odd thing to brag about, but hey, it's Texas.)

Regardless of the rating, it remained the single most destructive U.S. tornado until the Moore/OKC F5 of 5/3/99. The important thing is that I don't believe the city received any less assistance (or any less national publicity) because the tornado wasn't rated at the maximum possible strength. The damage spoke for itself, as Katrina's damage will continue to do.
I was going with the data, adjustments for the fact that the instruments mostly broke and the speed/trajectory of the storm, and came up with these estimates for sustained winds based on where the center of the storm was relative to these locations:

Starkville, MS (G76, left) - 65 mph
Meridian, MS (G80, broke, right) - 75 mph
Laurel, MS (G110, broke, right) - 90 mph
Poplarville, MS (G136, broke, left) - 120 mph
10 miles N landfall (based on Pascagoula - G121, broke, well outside eyewall) - 135 mph
Conclusion for MS landfall - 140 mph
it is comeing down hard with a lot of lighting aroud
109. code1
DCexTexan, exactly chaser and other's point. Sorry you had to go through that.
CrazyC83, I have exactly the same estimate after looking at numerous wind reports, equations, images and infrared movies.

Buras, LA - 150 mph (based on reverse inland decay equation)
Pearl River, MS - 140 mph (based on a lot of wind reports and other data)

I think you are right on target with your estimates
The Buras landfall is a guess based on the decay model (as there is no data to back up any estimates). I have 150 mph down as my estimate there too.
WOW what a t-storm
Wow, that report by the nhc is a load of garbage. pretty much everyone they talk about concerning pressure, windspeed and storm surge indicate that it was CLEARLY a cat 5 at landfall. What garbage. Great analysis Jeff Masters as usual.

here are a couple of the outstanding points that made me laugh.

"No storm surge data was presented for New Orleans. No mention was made that Katrina, despite its Category 3 strength at landfall, pushed a Category 5 level storm surge to the coast. The report noted that official storm surge measurements were unavailable, due to failure of most of the tide gauges. However, one unofficial storm surge height of 27 feet at the Hancock County Emergency Management Office in Mississippi."

"Katrina officially made landfall at Buras, LA, with a central pressure of 920 mb. This is the third lowest pressure on record for a U.S. landfalling hurricane, surpassed only by the two Category 5 hurricane to hit the U.S.--the Florida Keys Labor Day Storm of 1935 (892 mb) and Hurricane Camille of 1969 (909 mb)"
^^^^^^^^^^^^^
This above especially is ridiculous as it came in third place as the low pressure read hurricane to hit the US. And guess what 2 are ahead of it? 2 onceina century type hurricanes...

The lowered wind speed may make some sense because of this. With Katrinas catargory 5 massive status in the atlantic basin, she was powerful enough so the winds managed to die down, however the storm surge and min pressure at landfall did not.

In conclusion, the only reason this storm is not a catagory 5 at landfall, and only a cat 3 is because of the insurance issues. We had some nasty storms this year no doubt, Dennis, Rita, Katrina, Wilma that hit the US coastline. And those are only the strongest ones. It was a year to remember forever in the Meteorolical world, and we should look back on it and think of the people we lost, not how this storm was downgraded.

Nice 88889, im a little north of san francisco and we've had a steady mist all day long. Only until this evening have we had some heavier rain, i want some thunder. how is it over there? Looks like on the radar the sacramento area is getting some heavy stuff.
Trouper, PLEASE sign and comment in my petition blog.
Will do torn, its well deserved. It almost looks bad, considering the loss of life and damage the storm caused, only having it at a cat 3. whats going to happen if a cat 5 hits us? Damage should be almost twice as bad lol. This is hilarious.
"[...]but all 11 hurricanes with pressures less than 973 mb that have hit the Gulf coast the past 20 years have weakened in the 12 hours prior to landfall."

Slight error here. All 11 hurricanes that have hit the NORTHERN gulf coast have weakened...Charley and Emily are a couple of examples which didn't.
Trouper415 we this got a big t-storm
Hey Colby, will you sign the petition?
hey tornadoty i post in your blog about the K storm did i do it right?
hey guys whats up man its been stormy all day here
hey david did you get any of this stormy weather we got thunder very heavy rain and the works
hey theboldman we are haveing a good lighting show her
yes got a got lighting show for the 3rd time this year hail and lots of rian
oh thats cool david we got that this morning and this afternoon plus flooding rains i do see its all sunk south now i think im in the clear you still have a while to go
this t-storm dos not want to ene
but it was amazing to have it on the first day of winter

yes it is what more can yo have for the last few days of 2005
i dont know david more rain i think were supposed to get more rain 2morrow
yes we will get rian but i want some low snow
Guys, hope I don't offend you great guys, but do you mind if I do a spelling and grammar check before I send the petition to the NHC?
tornadoty how was my?
tornadoty you can fix it up a little bit uif they need it
It was good guys. I'm just going to clean them up a bit. They are old men, we have to remember.
tornadoty was my ok and did i do it right
YES COLBY!!! And what about Camille??? NHC have so much to answer for
KWRZ, I love what you said, but I am just going to clean it up for the old geezers at the NHC. I hope you don't mind! I will check with you to make sure you approve of any changes before the petition is sent.
Frederic was also strengthening upon landfall.
tornadoty you may fix it up has march as you like what did you like at it
Also, Camille was beginning its weakening at landfall. The pressure had risen from 905 mb to 909 mb, leading me to believe that it was on the cusp of beginning an eyewall replacement cycle.
tornadoty do you think that the nhc would look at all of are e mail and get back to us
I think (hope) that we are at the very least spurring deep thought.
Did you get to read the letter I sent the NHC earlier today?
tornadoty well i think i am going to call it a night and get some ZZZZ so go fix up where ever you need to fix up on my post send me a e mail of whe you fix up i will look at it and i will get back to you has soon as i can
tornadoty no i did not can i see it be for i go to bed
Wednesday, December 21, 2005




To whom it may concern:

I have read the National Hurricane Center report on Hurricane Katrina, issued Tuesday, December 20th, 2005. I have a couple nagging questions that I feel must be answered concerning Hurricane Katrina.

1. In section b, paragraph nine, sentences ten and eleven, it is mentioned that sustained Category 4 winds of 135 MPH (115 kt) may have reached the southeastern coast of Louisiana . If this did occur, would Katrina not count as a Category 4 strike on Louisiana?

2. I understand how the expansion of the pressure field could lower the winds in the hurricane. However, I was looking at the advisories and report on Katrina and comparing them to Hurricane Ivan of last year and I noticed a few things that puzzled me:

a. When Ivan made landfall on the Alabama Gulf Coast last year, it had winds of 120 MPH, a pressure of 946 mb, and a maximum hurricane-force wind radius of 105 miles. According to the Katrina report, the winds at landfall were 125 MPH, the pressure was an incredible 920 mb, and the wind field was 120 miles at the Buras, LA, landfall. Was the fifteen-mile difference in the radius of the wind field really enough to counteract the huge 26 mb difference in pressure between the two hurricanes and bring the sustained landfall winds so close together? I understand the effect that pressures in the surrounding environment of a hurricane affect the wind speeds in a hurricane, but were the environments surrounding each hurricane different enough to cause this large difference in pressure and wind relationships in the absence of a large difference in the wind fields?

b. The authors of the report explain on page 9 of the report that the huge surge of Katrinas was caused by a large Category 3s storm surge and the large wave action of up to 50 feet prior to landfall. The surge of Katrina, according to the report, is at least 28 feet. Hurricane Ivan produced an unofficial wave height of 131 feet over the Gulf, with numerous reports of 50-60 foot-tall waves. I know that the topography near the Mouth of the Mississippi River is a more surge-vulnerable and surge-enhancing area, but why is there a 12 feet+ difference in surge if Katrinas was enhanced by wave action? Wouldnt Ivans be higher if the wave action played a large role?

Thank you for taking time to answer these questions.



Sincerely,
Anthony Lyza
tornadoty wow i hop the nhc get back to you did you see my last post


osted By: KatrinaRitaWilmaZeta at 4:48 AM GMT on December 22, 2005.
tornadoty well i think i am going to call it a night and get some ZZZZ so go fix up where ever you need to fix up on my post send me a e mail of whe you fix up i will look at it and i will get back to you has soon as i can

did you see this part yet?
Good night KWRZ. And to all of you also. I'm hitting the hay.
well good night tornadoty and oh ever is on her
Good morning everyone,

Since I will be away until the 30th and won't be able to post I would like to wish all of you a very merry Christmas. As soon as I get back I will continue with my blog entry on Hurricane Katrina.

Thank you everybody and enjoy the holiday period

Rich (Atmos)
151. code1
Merry Christmas Atmos! Good to have you back. Be safe on your travels this season.
I think after seeing these devestating hurricanes the past two years all of us have to realize there isn't an "exact" to what each catagroy a storm can do. In Punta Gorda wheere I live on the water a "normal high end Cat 4" storm we would all be under water from the surge. The highest elevation home is at 10 feet. But as you know with Charley due to its size, fast moving and strengthening ect.. we didn't get the deadly surge just the wind damage. But now only what 18 short months later the majority of the clueless in town say oh well we lived through Charley and look we are still here. I always voice my opinion saying yes but remember if it had been a "normal Cat 4 the whole county would have been washed away. And they still don't get it.... Hello???
Dear NHC,

We require an explanation, given in a sound, scientific manner, and supported by verifiable, objective evidence, regarding the following two things:

1. How you arrived at your final landfall wind speeds at Buras, LA and the MS Gulf Coast, when numerous measurements from inland stations at different points along the storms path clearly indicate much higher wind speeds at landfall.

2. How a supposed "Category 3" hurricane, with a landfall strength and windfield size comparable to Hurricane Ivan of last year, carried a surge almost twice the height of Ivan's into the Gulf Coast.

Sincerely,

TampaSteve
SWFLKR wrote:

" think after seeing these devestating hurricanes the past two years all of us have to realize there isn't an "exact" to what each catagroy a storm can do. In Punta Gorda wheere I live on the water a "normal high end Cat 4" storm we would all be under water from the surge. The highest elevation home is at 10 feet. But as you know with Charley due to its size, fast moving and strengthening ect.. we didn't get the deadly surge just the wind damage. But now only what 18 short months later the majority of the clueless in town say oh well we lived through Charley and look we are still here. I always voice my opinion saying yes but remember if it had been a "normal Cat 4 the whole county would have been washed away. And they still don't get it.... Hello???"

AMEN, brutha! My in-laws live in PGI...I agree 100%!
Good morning everyone,

Hope everyone is haveing a good day. For Southern California a large high sits over the area like a huge brick. In Southern California my christmas tempture will be in the 80's. Thats not holiday like :-(. I remember last year winter kicked into high gear the day after christmas where we had on and off rain from the 26 of December tell January 10th if my memory is correct. I also beleave that the city of LA got the second most amount of rain ever in a 24 hour period someing like 5.30 inces. For LA that is something I would probally never see again if I lived around the area for the rest of my life.

This year however I have already wrote off this winter as below normal and am looking toward next year.
Hey Code1, Merry Christmas! Email me sometime :-)
AMEN, brutha! My in-laws live in PGI...I agree 100%

Tampa Steve
I live in PGI too. All of PGI would be gone if Charley had the "normal" Cat 4 surge. I might not be here today. We rode out the storm in the closet with life jackets, pool floats and an ax to take to the attic if needed. God, what a day I will never forget. I will definitely not stick around for anaother and risk it ever again. I have had motel reservations made for every storm after Charley and will do the same next year.Where do your in laws live? We are renting a place over here and moved in two monthes before Charley roared through. Oh by the way I am a sista LOL
Wow...looks like NHC stirred up a hornet's nest. I think that what this all shows is that the current classification system is need of an overhaul. Hurricanes are very dynamic events. Wind speed, wave heights, storm surge are all variables that the current system does not address as a whole. Downgrading (or upgrading) a storm does not change the effects of the storm. It did what it did, and what government officals (and blog commentors) think don't change that. What really needs attention to prevent this in the future is the tools we use to monitor weather. What all the instruments that failed show us is that we have a system that is not designed to withstand the actual weather it may encounter. I lost a house and half my possessions to Frances and Jeanne, and it's irrelevant how they were classified. Changing a number does not change what happened. The classification is NOT the storm. The storm is the totallity of all the things that everyone here has mentioned, and then some. As a final example, there has not been much mention of rainfall totals, yet that is sometimes more damaging than the winds for people inland. (I lived through Agnes as a kid well inland from the Chesapeake Bay, yet lost some friends to flash floods from rainfall. My guess is this debate will go on for years. It won't change anything for those that lost everything.
You're partly right about Charley, although it was also a very small storm in size, which didn't get the wave action going. That was basically the opposite of what happened with Katrina. It was more like a 20-mile-wide tornado than anything...
Looking at Katrinas amount of damage and destruction to me is amazing. I live in Cozumel and we were here on the island for Wilma. Wilma stayed here for close to 50 hours at CAT4+ and we did have a lot of damage but nothing compared to New Orleans. I am thinking it must be because everything in mexico is concrete and we dont have many tall buildings.

Bill
www.guide2cozumel.com
Here is some information I hope will clarify a lot of the questions about Katrina's surge. In order to visualize it, you'll have to go to those links and at least give them a cursory glance. On the HES tool, disable evac zones and enable flood zones, to see the five levels of surge.


Notes on Katrina's surge levels

Not all of the information on Katrina's surge along the MS Gulf Coast has been made available. The initial NHC Katrina report did not go into extensive detail about the surge.

High water marks do not by themselves denote surge levels. High water marks, especially outdoor ones, also include height from waves. Waves right at the shoreline can be quite high. Allegedly a DVD with amateur video which was distributed locally in limited quantities in MS, showed approximately 30 foot waves at the shore in Gulfport. Wave estimates at the shore there were already in that range; waves on top of the 20+ foot surge there were large enough to wash all the dolphins out of their 30 foot high tank at the marina. However wave action, even as small as half a foot, can travel very far inland. Tides are also a factor in computing the actual surge. Tides along the MS Gulf Coast are not a significant factor; the different between high and low tides is only a couple of feet at most. This factor is easy to take into account as the times and heights of high and low tide are known. These factors must be subtracted to obtain the water height generated from the hurricane surge.

Just as with sustained wind values, identifying the highest level of surge is not the same thing as saying that level of surge occurred everywhere. It is important to quantify the extent of the area flooded by each category of surge.

We can make an unofficial but informed guess as to what areas of the MS coast received what categories of surge, based on information currently available, with the caveat that it may be changed later, and we are not 100% certain of its accuracy.

What tools are currently available on the internet to determine this information?

First, FEMA has published maps of the surge on the MS coastline. These maps show an extremely limited number of high water marks, mostly outside, and that information is too sparse right now to give an overall picture of the surge. Along with these selected high-water marks (which the NHC Katrina report may possibly have implied are not valid because the wave and tide levels have not been subtracted yet), the FEMA maps show all areas which were flooded, by some level of water, by the surge. This may mean only one foot of water from surge (as in the parking lot of the Jackson County sub station in Ocean Springs), to 25 feet of water from surge (as along the southern coast of the Waveland / Bay St. Louis area).

http://www.fema.gov/hazards/floods/recoverydata/katrina_ms_index.shtm

Second, we can use detailed online elevation maps such as Topozone, to identify the elevation at any location along the coast.

http://www.topozone.com

Third, we can use the Hurricane Evacuation Study (HES) maps for Mississippi, from the USACE web site. These maps were generated from SLOSH runs (the parameters for the runs are documented as well), and seem to be extraordinarily accurate. These maps show what areas of each county, down to individual addresses, would be flooded for each of the five hurricane category classifications. The HES maps do not show a range of heights associated with each hurricane category, and there is a good reason for that: the height differs with each location based on surrounding topography.

http://ekman.csc.noaa.gov/website/FEMA_EvacZ/AddressPage.htm?state=mississippi

By comparing the elevation maps to the HES maps, we can determine at what level each category of surge begins, based on the location. Thus, Category 4 surge begins at 21 feet for BSL, Pass Christian, and Ocean Springs, but at only 15 feet for Pascagoula. This last may have been an error on the part of the model, underestimating the vulnerability of this location, because these Cat 4 levels on the map were flooded, or there may have been certain characteristics of the surge that resulted in an anomaly with higher surge here, because the flooding of the Pascagoula River Basin in general was extreme (
http://www.nasa.gov/vision/earth/lookingatearth/h2005_katrina.html ).

Fourth, FEMA has also provided an overview map with their estimates on the height of the surge across the MS coastal region.

http://www.fema.gov/hazards/floods/recoverydata/pdf/ms_overview.pdf

Finally, to back up the FEMA flood maps, we can go directly to the aerial images from NOAA taken shortly after the event (but of course this would be after most of the floodwater had receeded). It cannot always be seen from these maps which areas were flooded. Some places, such as in a large part of Hancock County, everything is covered with mud, but other places will have not discernable sign, and you cannot always go by the debris line as an indicator either.

http://ngs.woc.noaa.gov/katrina/


Based on this information, and assuming it to be accurate, we can answer the following questions:

What areas of the MS coast experienced Cat 3 level surge from Katrina? What areas, if any, had Cat 4 level surge? Cat 5? Where did this occur, and how large were these areas?

This is not completely straightforward. It is clear that the highest level of surge did not go very far inland. All of the areas that experienced the highest levels of surge were right on the shore, and most are so low they already flood at Cat 1 level. For those we would want to rely on accurate high-water marks to determine what level surge occurred. But that information is not available right now. Luckily we can go by the FEMA overview map to determine where these areas are. Secondly we can look at the areas along the coastline that were at an elevation of Cat 4 or Cat 5, and see if any of these areas flooded. The problem with this method is that there is very little actual real estate along the entire coastline that is that high, as the MS coast is one of many areas in the US that is a flood plain. Also, these areas may not all be right on the coast.

In addition, the FEMA overview map only lists the surge in terms of feet. How can we determine what level of surge that corresponds to? Considering it can be different depending on location, we have to first use the elevation maps in conjunction with the HES maps to find out where Cat 3, Cat 4, and Cat 5 surges begin.

Before we get into this level of detail, we find that at a high level, comparing the FEMA overview map to the HES map, solid Cat 3 surge occurred along the entire MS coastline. This Cat 3 surge finally ended, inland, just NE of Pascagoula City limits, at around 611 and Old Mobile Hwy. The extensive amount of land to the south of that location, all the way into AL and to Mobile Bay, was at Cat 1 and 2 level, and was all flooded. So the Cat 3 surge ended inland, just miles short of the AL border. Cat 1 and 2 surge extended eastward into Alabama. On the western edge of the MS coast, in Hancock County, the surge ended just south of the NASA Stennis facility on the MS / LA border, and just north of Kiln and the Diamondhead areas. The most extensive area of inland surge was on the eastern edge of the MS coastline, along the Pascagoula River Basin, and this is predicted on the MS HES maps.

This, just by itself, is really the most remarkable thing about Katrina's surge: the extent of the Cat 3 surge, not the small area that may have been affected by higher Cat 4 or 5 surge.

Did any of these areas at higher surge levels exist?

We know from the overview map that the highest levels of surge, in feet, were along the southern shore of the Waveland / Bay St Louis area, the Diamondhead bay shore area south of I-10, and an area of the coast from about Menge Ave in the Pass, east to the Long Beach / Gulfport border, so we can decide that the coast on either side of Saint Louis Bay is a good place to start identifying the highest level of surge.

Also, we can use the MS HES maps to locate any land that is at Cat 4 or Cat 5 surge level in Hancock and western Harrison Counties. We find that there are very few areas and that they are very small. Just south of the BSL bridge we find the eastern end of four small city blocks that are at Cat 4 level right along the shoreline. Another area of land that will not flood until Cat 4 or Cat 5 level is SW of there, and runs inland, parallel to the southern shoreline, cutting across the man-made lake for the water treatment plant (an easily-found location on a map). The remainder of the Hancock County shoreline, and quite a ways inland, will flood with a Cat 3. In western Harrison County, along the shoreline, we find only one narrow area, starting just west of Menge Ave in Pass Christian, that runs east along the shoreline into Long Beach, Gulfport, and Biloxi, that will only flood at Cat 4 or Cat 5 level.

Locating these areas on topozone.com, and following the brown elevation lines (which are given every five feet, for instance 15, 20, and 25 foot elevations), and comparing with the MS HES maps, we can make a general assessment at what elevation Cat 4 and 5 start for these particular locations. We find that it looks like Cat 4 starts at around 21 feet in elevation in both places, and Cat 5 at 24 feet for BSL, and 25 feet for the Harrison County area previously mentioned. This is a guess, but is probably not off by more than a foot.

Now, we can use the FEMA flood maps to see how much of each of these areas did actually flood.

In BSL, we find that everything was under water except for most (but not all) of the areas that only flood with a Cat 5 surge. We find that the 25 foot surge identified on the FEMA overview map did not reach far enough inland to affect any areas that were not already flooded. We find that all the tiny areas of land at Cat 4 did flood, and the edges of the Cat 5 area around the water treatment plant flooded. So we know that the highest surge in this area was approximately 24 to 25 feet. Perhaps the area on the Waveland / BSL coastline received higher surge, even though they were already well under water, but we will have to wait for accurate high water marks to assess that.

In eastern Pass Christian, we find that the areas that are at Cat 4 level flooded, but the strip of land at Cat 5 level (beginning at 25 feet of elevation) did not. Since this area is right on the shoreline, we can conclude the surge there reached 25 feet but did not go much over that, if any, and most likely did not reach Cat 5 level.

We can conclude that very small areas of the MS coastline, most likely less than one percent of the land on the MS coast that was flooded directly from surge, were subjected to a surge that just barely edged over the Cat 5 level, although the total area receiving surge at the Cat 5 level was so small compared to the total area of land inundated by surge, that it is almost negligible, statistically speaking. Most of the area receiving a Cat 5 level surge was already so low that it was well underwater, the difference in the height of the surge was probably not a significant factor in incurring the total property devastation, but, if it can be quantified, will be useful for denoting the record height of the surge. Another small area, bordering that, perhaps a couple percent of the total area, received Cat 4 surge. The areas that were on the shore were also devastated by waves on top of the surge.

The majority of the coastline received Cat 3 surge, and the area receiving this level of surge covered a wide range that was unprecedented, spanning the entire MS coastline, and reaching inland a considerable distance along all but a few miles close to the AL border. The area receiving Cat 1 and 2 level of surge was even more extensive, reaching completely to the northern Jackson County border, in eastern MS, and into AL, crossing Mobile Bay.

If you want to know more about SLOSH modeling, MEOWs and MOMs, search GOOGLE online, or go to the HES home page at USACE. A mathematical grid is used to represent a particular coastal basin, and modeling is done for a number of hurricanes at different tracks and intensities. The worst case flooding scenario (basically, the MOM, or a group of MEOWs) is identified for any location, from the sum of these modeling runs.
SLOSH - Sea, Lake and Overland Surges from Hurricanes

MEOW - maximum envelope of wind

MOM - maximum of MEOWs
Hellooooooooooooooooooooooooo! Is anyone home?
hey tornadoty what up
Awesome post, squeak! Thanks for the research and explaination. It was a little hard to follow - I made some images to try to keep track, using screenshots of maps and such, but I wasn't completely sure of the locations you were talking about. If you want them as a starting point to illustrate your post, I can email them to you or something. :)
I have the petition thus far updated on my blog.
You can use mapquest to aid in locating streets or cities.

I didn't write those last paragraphs very clearly. Here is a rewrite to sum up the areas with Cat 4 and 5 level surge:

We can conclude that one very small area of the MS coastline, the immediate coast of Waveland and southern BSL, was subjected to a surge that just barely edged over the Cat 5 level. This area was so small compared to the total area of land inundated by surge, that it is almost negligible, statistically speaking. The elevation of this area was already so low that it was well underwater, the difference in the height of the surge was probably not a significant factor in incurring the total property devastation, but, if it can be quantified, will be useful for denoting the record height of the surge.

The areas that received Cat 4 surge were Waveland and the part of BSL that curves into the bay and GOM, and a small portion of coastline along eastern Pass Christian, to the Long Beach / Gulfport border, and Diamondhead area south of I-10.
my new blog is up so when ever some one come on the blog stop by my blog to see if you like if you post and i am not there that mean i am in bed or not aroud to get back to you so this post what ever you like then i will get back to you on your post as soon as i can

so good night all
Hey everyone,

I have just created a new blog relating to global warming and whose responsible for it. I believe everyone will at least find it interesting reading whether they like the contents of it or not.

Here is the link to my blog.:)


I'm sorry about that. I had lost the link to my blog. I want to take this opportunity to wish everyone and their families a safe and very Merry Christmas.:)

Link

Your friend,
Tony


This whole set of posts make very interesting reading.

I have only a couple comments. First, I read the NHC report before coming here, and I found it interesting that at least a couple of the unofficial reports of wind speeds, especially in FL, were taken from wunderground.com. I guess it is fair to say that NHC knows we are out here and have at least some respect for what members are doing .

The other thing that struck me is that consistently NHC is unable to report accurately regarding wind speed, wave / surge heights, etc. because THE MEASURING EQUIPMENT FAILED!!!!! If anybody is writing to the NHC, someone should be querying that little fact, with a view to finding out what is to be done about it. I think it is ridiculous that more than 100 years after Galveston there are still no accurate, DURABLE measuring tools on the ground.

Rather than disputing over the accuracy of landfall intensities, we all should be encouraging the "powers that be" to actively seek avenues whereby the quality of reporting in future storm events can be improved.
That is because hurricanes are destructive and debis can blow onto them,that is why we need reporters to be ther,to me as long as they are there in a safe place it is fine,me myself like doing it.Aso mant times the reportys reporting in the hurricane wanted to be there,radars and observations alone,bassically lie to you when it comes to hurricanes.Sattelites and live on the scene reporters are the most accurate tools of teling how bad a hurricane really is.Now I do think it is silly when they are way out in the open without a sturdy structure to take shelter in when it gets real bad,but as long as they are in a safe place it is in some ways needed,and absolutely fine they are there.So for y'all that are against it totally,I will not fight with y'all on this issue,but think about it a little better before you speak.
By the way that is false,the surge from katrine was measured over 30 ft which is almost double of what the minimum is required to be category 5 surge of 18 ft.It was widespread more than 15 to 20 ft not just a very small area.I don't know where you got that info from bvut it is not accurate..
This is very simple. There is a huge political pressure to blame someone for the mess in New Orleans. People need a scapegoat, something or someone to blame for a disaster, even one such as this which is simply Mother Nature at work.

Personally I believe the storm was a cat 4 at landfall, it's satellite presentation was more consistent with a 4. However we cannot know for certain... even at Cat 3 speeds winds instruments are destroyed and operational data is sparse and often inaccurate.

But that's not the point. This has nothing to do with data or analysis... this is a purely political move probably motivated by pressure from certain factions within the government. There is a huge drive to blame Bush and the Army Corps of Engineers for this disaster. This drive is especially strong in academic sections of the government... in other words, including the NHC. By downgrading to a Cat 3, regardless of whether or not it is true, the NHC creates ammunition for the media to put pressure on the federal government to pay for the disaster.

This is the real reason, and let's not kid ourselves by saying it has anything to do with the data. The NHC, along with some other organizations within the government, want to put pressure on the Bush administration. By blaming the Army Corps of Engineers for the levee failure and Bush for not spending federal money on them, the NHC along with the LA government and many others want to create a situation where Bush and the federal government must pay massive compensation to the victims.

I've heard a lot of arguing about wind speeds and storm surge, etc... but truth be told, Cat 3 or 4.. it doesn't matter. The storm was massive, powerful, carried a huge surge and destroyed New Orleans along with whole sections of Mississippi. We already know this, and political stupidity aside it doesn't much matter what us mere mortals rate a disaster. It is what is.
xealot: Yup...it's politics, pure and simple...