1992 Andrew report update

[Pearl River]

Derek Ortt wrote

Based upon recent hurricanes, it is safe to say that if we can protect the northern GOM from a category 3 hurricane, that region will be safe. Had the New Orleans levees actually been designed to withstand a real cat 3 storm surge (not the 9-12 feet south florida/puuedo 3 indicated in the unofficial addition to the SS Scale), we would not have had the tragedy of New orleans

New Orleans levees were built to withstand cat 3 storm surge. Unfortunately years of subsidence, a barge thru one of them and just plain neglect by the Army COE caused the flooding in New Orleans. And another thing, contrary to popular belief, the levees did break during Katrina, not the day after.

[Derek Ortt]

I know they broke during the hurricane... not sure who stated they broke after.

Some of the levees, especially the industrial canal, were overtopped, which means they were too low. If they were build to withstand a maximum surge of 12 feet, they were built too low as computer simulations and previous hurricanes indicate that this is the values of a mid category 2 hurricane for this part of the Gulf Coast (Georges produced up to 15 feet in MS)

[Aslkahuna]

Storms tend to weaken prior to landfall on Taiwan and Luzon strictly due to land interaction as the terrain is very rough and tends to rise abruptly from the Sea. This really messes up the inflow and storm structure. An approach to China that bypasses Taiwan is very similar to the approach to the Gulf Coast with a generally low flat coastal plain, a large river (the Yangtse) flowing into the Sea and shallow shelf and the fact that the storms have moved past the warmer waters of the Kuroshiro Current. Dry air entrainment from off the mainland-particularly later in the season, and land interaction where the onshore portions of the storm are now longer drawing heat form the Ocean but rather loosing it to the raincooled land (also frictional effects).

Steve

[Derek Ortt]

thanks for the info regarding China. Did not realise how similar it was to the Gulf Coast

[HurricaneBill]

Wouldn't it be better to protect against a Category 4?

Even if hurricanes usually weaken to Category 3 prior to landfall, what about the ones that are in a strengthening process?

I still think it might be possible, if condiions are right, for a low-end 4 to make landfall.

[AussieMark]

Derek

wasn't Frederic a uppper 3 or low end level 4 or do u think Frederic will be reduced?

[Derek Ortt]

frederic appears to have been in the 110-115KT range. They seem to have that one correct (about as strong as indicated

I see the point about protecting the city against a 4. We always could get the odd very large, fast moving cyclone moving at 315, keeping it over the warm waters the longest and get a low end 4 at landfall. No matter how unlikely this scenario is, it is plausable; thus should be prepared for. Andrew seemed to have the best chance to hit the GOM coast as a 4 and a faster motion would have brought it in as a 4. Therefore, you are right, Hurrbill

[aerojad]

Dry air, much lower heat content, cooler waters. I expect each and every landfalling major GOM hurricane to be a Cat 3, and no higher from now on.

Unless there's a forward speed over say 20mph.

[mtm4319]

frederic appears to have been in the 110-115KT range. They seem to have that one correct (about as strong as indicated

I see the point about protecting the city against a 4. We always could get the odd very large, fast moving cyclone moving at 315, keeping it over the warm waters the longest and get a low end 4 at landfall. No matter how unlikely this scenario is, it is plausable; thus should be prepared for. Andrew seemed to have the best chance to hit the GOM coast as a 4 and a faster motion would have brought it in as a 4. Therefore, you are right, Hurrbill

And, of course, considering Camille was likely a 4.

[Pearl River]

Derek wrote

know they broke during the hurricane... not sure who stated they broke after.

Some of the levees, especially the industrial canal, were overtopped, which means they were too low. If they were build to withstand a maximum surge of 12 feet, they were built too low as computer simulations and previous hurricanes indicate that this is the values of a mid category 2 hurricane for this part of the Gulf Coast (Georges produced up to 15 feet in MS)

Here is a link to the Army COE site. The minimum elevation shown is 13.0 ft. The earthen levees held fine, it was the levees along the canals that breached. Subsidence was a big issue with these, due to the fact they were made of concrete and steel pilings and poor maintenance. The MR-Go was also a major contributing factor. The lower 9th ward area was in the 14 ft levee height area along the Industrial Canal.

http://www.mvn.usace.army.mil/pao/response/Lakeview.asp

[JonathanBelles]

list all of the changes made to andrew

[mike815]

yes please list them someone that would be great.

[HurricaneBill]

Wasn't Elena in 1985 taking a dangerous path towards New Orleans? (After she had stalled off the Florida coast; She was all over the place!)

[RattleMan]

Wasn't Elena in 1985 taking a dangerous path towards New Orleans? (After she had stalled off the Florida coast; She was all over the place!)

Yes:

[Brent]

list all of the changes made to andrew

According to the link, the last update was February 7, 2005.

[mike815]

yeah thats what i saw too

[MGC]

Downgraded Louisiana landfall to 100KTS. Interesting point, at simular pressures, about 922mb, Andrew had 35KT higher winds.......MGC

[JonathanBelles]

i dont have the time to read all of that

[Derek Ortt]

the strange thing is, that link to the update was not placed on the report until this week

[Pearl River]

HurricaneBill wrote

Wasn't Elena in 1985 taking a dangerous path towards New Orleans? (After she had stalled off the Florida coast; She was all over the place!)

One of her forecast tracks was to take her right thru Lake Borgne, the Rigolets and into the center of Lake Pontchartrain. I lived in Slidell at the time, right on the northshore of the lake, and remember the police coming thru my neighborhood on their loudspeakers asking people to evacuate. This was at 1:00 am the morning of her later landfall on the MS coast.