Hurricane Katrina & Rita Reports

[jeff]

I have completed a post storm report on Hurricane Katrina. It is 46 pages in PDF format detailing the met history, the evacaution, levee failures, the damage by county and parish, damage to the oil industry, lessons, and a comparison to Camille.

If the web folks would like to put it on the website this is fine with me, if not send me an e-mail and I will forward a copy of the report to those interested.

Jeff. jeff.lindner@hcfcd.org

[Camille_2_Katrina]

outstanding!

i hope they let you post it!

[jeff]

A report on hurricane Rita is also completed detailing the meteorological history, the evacuation, damage by County and Parish, comparison to hurricane Audrey, and lessons learned.

[Margie]

Jeff, left you an email regarding the Katrina report.

Many good points in the report.

The specific areas that need to be looked at again:

Basically all the information on surge is wrong (the "Lesson 3" section). And SSHS is not used at NHC for surge, even though the original SSHS scale is listed on their web site.

If IPET was your source on data for Plaquemines and St Bernard, be aware of the issues between the various vertical datum (subsidence).

Also consider defining "destroyed" in the document and you may want to double check those "destroyed" home numbers listed in the report, with Jackson County officials. A home doesn't have to be reduced to a slab to be destroyed. Four or five feet of standing water can destroy a home and leave it standing, and, after the water marks have dried, leave it looking even normal from the outside. However, the inside will either be covered in mold, or gutted to the studs and have to be rebuilt. Basically...90% of homes in Pascagoula were destroyed, even up into Pinecrest. Out of those 90%, very few left with just a slab. So it would be better to clarify if you are only referring to homes that were swept away, or are including those that remain but were still destroyed (note the FEMA data in this area is likely wrong...was never changed from the initial estimates made only days after the hurricane hit).

[Lindaloo]

I am sure he researched all this Margie (see his professional met badge)?

[vbhoutex]

Margie, instead os sitting back and telling a professional met who does this work for a living that his information is wrong and leaving it at that, why don't you post the information that proves it is incorrect? Your statements are worth nothing without proof!!

[Margie]

Margie, instead os sitting back and telling a professional met who does this work for a living that his information is wrong and leaving it at that, why don't you post the information that proves it is incorrect? Your statements are worth nothing without proof!!

Well, he did ask you to post the report and you haven't.

It does get better...he's in flood control.

Ok, you wanted to know...this statement:

"Katrina’s large wind field and powerful intensity while over the open Gulf of Mexico created a large water level bulge...the built up water level bulge when Katrina was a category 5 over the open Gulf of Mexico is why Katrina produced such an extreme surge."

Um, no. One atmosphere is the equivalent to about 34 ft of water (as divers know)...this is very close to one bar. To make the computation simple say the drop in pressure was 100 mbar. That is, the rise of water under the eye was not large, it was about 3 1/2 feet, and dropped off proportionately (nonlinearly) as the pressure dropped off from the eye. A good approximation...about 1cm rise for each mbar of pressure drop.

The bulk of the surge is not associated with the pressure drop at all (a common misconception among laypeople but it shouldn't be for a met...take the article from yesterday's Sun Sentinel where they quoted Stephen Baig correctly then put up an incorrect diagram of what causes surge). It is associated with the column of rotating water under the radius of maximum winds (RMW). This is not actually a column, rather more of a toroidal shape that is not uniform around the center, but for the purposes of this post let us treat it as one. While in deep water, water is driven in towards the eye, and is able to sink down in the column, and out the bottom, so it does not build up. The only additional height while out in deep water is the already-noted small amount of height due to the drop in pressure (you know I am sure I have posted this info before...also linked to the nice diagram on the hurricanetrack website). In other words, the water that will comprise the surge is not noticeable at all as a rise in water level while out in the "open Gulf of Mexico," i.e. deep water. There is no noticeable "bulge."

However once this rotating column of water is pulled up onto the shallow continental shelf, water that is driven towards the center by the winds cannot escape out the bottom. And friction with the shelf becomes a factor...the water wants to spread out, but can't (think of a spinning ice skater), and so it has to rise (conservation of momentum). This is the bulk of the water that will comprise the surge, and even if the winds weaken considerably, most of it will make landfall as surge. There is an additional component, which is water that is driven onshore by the winds to the north and east of the eye (for a hurricane making landfall to the north).

Because Kat's RMW was much larger than Camille's, the rotating water was greater in volume (Jeff Masters calculated something like 4x greater). But comparing the surge heights along the coast the curves are very similar (i.e, surge is highly dependent on topography). Still, undoubtably the winds in the 24 hours prior to MS landfall were certainly a factor in wave setup enhancing the surge to the east of center, probably several feet, even though the main component of the surge was the water brought up onto the shelf.

That is why the fact that the loop current eddy was so far north and so close to the shelf was the major player in Katrina's surge. Katrina strengthened just prior to hitting the shelf, and the winds were really coming down to surface level with Katrina (check out distant buoy readings from the weekend before she hit), which doesn't always happen, so there was opportunity for a lot of energy to transfer to the water under the very large RMW. That, and the timing (Katrina had just finished an ERC).

"Education of the public should be addressed to inform persons in the inundation zones of the...potential failures of the Saffir Simpson scale to appropriately predict storm surge levels."

No need for that as SSHS is not used to determine storm surge. And that, a met should know. I don't think the public needs to be "educated." I think there are things they would like to know, or to be made clearer. One word I keep hearing over and over on the coast is "surprise." So I conclude that storm surge risk can be communicated earlier and better, but that more understanding also needs to be done in how the information is perceived at all the different levels in the process and in understanding the rather complex motivations of people regarding hurricane evacuation.

An interesting note: Simpson's textbook does describe these components of the surge. It would be interesting to understand the history a little better, and the state of the science at the time Simpson put the surge range into the SSHS category descriptions (I know someone who is not only a met but I think a kind of history buff on meteorology so I'll ask sometime).

This is a simplistic explanation (which is about as far as I want to go with my understanding) which can certainly be treated with more rigor.

The reason I know this information even though I am not a met, is that after Katrina it was important for me to understand. It is my coping mechanism, and I believe that without knowledge we really can't make things better (and this isn't just scientific knowledge; people are just as interesting). I would have learned it all eventually anyway because of my interest in tropical meteorology, which started last July, but dealing with Katrina sped up the process considerably.

[vbhoutex]

What does 'he's in flood control" mean? You post it as if it is some kind of derogatory remark like it means he isn't a Professional met or doesn't know what he is doing. I know full well he is in FLOOD CONTROL. He is the meteorologist for a local flood control district and is responsible for the flood watches and warnings being issued in conjunction with the NWS here in Houston. He knows full well what he is doing. Just because your "coping" mechanism and your research tells you something is different from what he posts/reports does not mean it is wrong!!! Sorry, but I will take the word of a Professional Met(yes we do determine that the credentials are real before the Pro met tag is used)who has proved to me and millions of others in the Houston area that he knows what he is doing many times over before I will take the word of someone from Minnesota who has proved nothing to me.

[Audrey2Katrina]

Katrina strengthened just prior to hitting the shelf, and the winds were really coming down to surface level with Katrina (check out distant buoy readings from the weekend before she hit), which doesn't always happen, so there was opportunity for a lot of energy to transfer to the water under the very large RMW.

All this is, is parsing words... the bottom line is that her intensity DID rise enormously and denying that this was pivotal in creating the scenario for her ultmate surge is preposterous. As far as your RMW that is a semantic jostling of the "massive wind field" he alluded to. Bottom line is that the essence of what he stated is substantiated even by all your verbiage. You know, it's okay to disagree, even with a pro-met, (I have on numerous occasions) but there's a way to respectfully disagree, and then there is patent condescension:

Um, no.

often combined with insult:

a common misconception among laypeople but it shouldn't be for a met...

and

No need for that as SSHS is not used to determine storm surge. And that, a met should know.

Quite frankly he did not say or even imply it IS used to determine surge; but only that it fails "to appropriately predict storm surge levels." You're attacking a straw man, and while some lay persons mightn't know this, someone with your obvious epistolary skills SHOULD know it.

Since many lay people DO use the SSHS to "predict storm surge levels" his point is quite valid, and your essentially cheap shot is just another example of the colossal hubris typified in just about everything I've read in your posts. Why must it always appear as if you're talking down your nose to the ignorant masses? Apparently humility and a tolerance for other viewpoints are just not in your lexicon!

As stated, one can disagree--but insult and condescension cross the line of civil discourse, I think Jeff has exhibited remarkable restraint in ignoring your posts; and perhaps this will get me a slap on the wrist as well--but I just couldn't let this kind of patronizing "I know it all, and you're just wrong" epistolary bunk go unchallenged any longer.

A2K

[Dionne]

Jeff....I'd like to read the Katrina report. I have sent you my email addy several days ago. Here it is again;

rdionne@bellsouth.net

Thank you.

[george_r_1961]

Margie I agree that onshore winds enhance the surge but the biggest part of the storm surge is caused by a dome of water rising inside cyclone in response to lowered barometric pressures. This "3 foot dome" as you put it contains a TREMENDOUS volume of water, not just the 3 feet of water above the surface. When that little dome of water gets into shallow water near the coast it rises as the sea floor rises too. Much like a tsunami does as it approaches the coast. In bays along the coast this surge can be compressed horizontally; and since the water has go somewhere it rises, further enhancing the surge. BTW im no pro met, not even close, but I did sleep at a Holiday Inn Express last nite.

[Audrey2Katrina]

but I did sleep at a Holiday Inn Express last nite.

A2K

[Ixolib]

[Audrey2Katrina]

Enjoying the show are ya, Ixolib?? LOL



A2K

[Lindaloo]

Margie I agree that onshore winds enhance the surge but the biggest part of the storm surge is caused by a dome of water rising inside cyclone in response to lowered barometric pressures. This "3 foot dome" as you put it contains a TREMENDOUS volume of water, not just the 3 feet of water above the surface. When that little dome of water gets into shallow water near the coast it rises as the sea floor rises too. Much like a tsunami does as it approaches the coast. In bays along the coast this surge can be compressed horizontally; and since the water has go somewhere it rises, further enhancing the surge. BTW im no pro met, not even close, but I did sleep at a Holiday Inn Express last nite.

LOL at the Holiday Inn Express comment.

[Lindaloo]

Margie, I would love to see your credentials. Thanks.

Just because you lived on the MS Gulf Coast eons ago does NOT make you an expert.

[Derek Ortt]

I have to disagree with the barometric pressure being the main factor regarding storm surge.

Many studies have shown that it is the onshore winds that do the trick. Of Katrina, the pressure may have added about 5 feet to the surge. It is mainly the size of the hurricane force and major hurricane force winds that produces surge, along with coastal topography

[terstorm1012]

I'm really looking forward to Jeff's report now...seeing the controversy! Email it to me when you get the chance, I imagine you're busy so there's no rush at all (I dropped you a line a couple days ago).

cheers and have a good one!

[jeff]

A few comments:

The lesson 3 paragraph may have been poorly written. I am well aware that the pressure did not create the catastrophic surge on the MS coast and that the SS scale is not used at NHC for surge prediction. A combination of the large wind field and coastal topography, along with other surge related factors produced the surge. My comments with the SS scale were completely aimed at the general public (what is printed in newspapers and on hurricane tacking charts). My point was to simply point out that the general numbers in such print media may fail due to various factors and complicated nature of storm surge prediction. Few people actually understand that the size of the hurricane wind field and coastal topography are hugh drivers in the surge height. This paragrahph was heavily debated with a couple of other pro mets which I had proof the report. In the end it was decided to let it go, although it for sure could have been written better and maybe explained clearer...there was a time issue at that point.

As far as the damage data...all data was complied from the state of MS SOC. I do not know what they considered destroyed...but it was given as destroyed in their situation reports. It should be clearly stated that the figures provided in the document may already be outdated and due to the staggering amounts of damage and widespread nature of the event final damage figures may not be known for several years if at all. The inundation areas were complied from the new FEMA advisory data showing the limits of inundation for both hurricanes Katrina and Rita. This was compiled from surveyed high water marks. IPET was not used for any surge related data across SE LA as it has not released their final report. I am also well aware of the vertical datum adjustements and the hell of correct datums in SE LA...it is a complicated beast.

Lastly, if the moderators would please remove any post related to the agency I work for. The views represented in both reports are my personal view points and in no way reprsent my employer. In fact I was only using that e-mail as a better service to everyone as I check that one more than my personal one (sorry I have been out since Thursday and have not checked my work e-mail).

[MGC]

Pretty much have to agree with Margie on this one sorta. The bulge caused by Katrina's low pressure did add to the rise in water level along the coast but was likely third in line in causation. Katrina's huge wind field of hurricane force winds along with the coastal bathometry were the leading factors to consider....MGC