Camille, Andrew--Cat. 5???

[gk1]

The NHC is off-base with the downgrading of Katrina--If anything, it should have increased strength to Strong Cat. 4 or more. They even admitted that sites and wind gauges were not working due to power failure. Pressure, Lost of Life, and Storm Surge were Unprecedented!!! They made a quick and insulting evaulation of Katrina in my opinion!!!

[wxcrazytwo]

There is nothing you can do about it. IO highly doubt Cat 3 winds did all that damage. I agree on your previous post, I think very strong Cat 4 winds. I think they will re-analyze this and get with the picture.

[P.K.]

The category of the storm is based purely on the wind. Even if you have a low central pressure if the storm is large winds will be lower than with a small sized storm due to the pressure gradient force. The storm surge would have built up during the time Katrina was at its strongest but isn't able to drop as quickly as the winds can. The loss of lives also doesn't affect the category of the storm.

Just shows how a storm that is "only" a cat 3 at landfall can do a lot of damage.

[Brent]

Show me some Strong Cat 4 wind damage...

Surge doesn't determine intensity, maybe it should, but it doesn't right now.

[MiamiensisWx]

Why is everyone forgetting the best example of what Category One and Category Two winds can do (Wilma)?

Also, when you have big surge like Katrina did, wind intensity goes almost entirely out the window. Weakening storms just before landfall often have produced some of the worst surges (e.g., an example besides Katrina is Ivan from 2004).

[Audrey2Katrina]

There is plenty of damage from Katrina by WIND alone North of Lake Pontchartrain--saying these were from cat 1 or 2 cane is imo patently naive.

I'll buy the pressure gradient argument when I see a documented map showing all of the isobars, hence the actual gradient spread from the storm. Is that available? I have no doubt the size spreads the winds over a larger mass of area, and hence the further from the center the smoother and less intense the change of windspeeds; but unless we can see the actual gradient around the center of circulation through a meaningful map displaying the actual isobars; simply generalizing by stating that size dispells intensity of wind speeds at a low pressure center of circulation is speculation. Someone here has said, show me the Cat. 4 wind damage... a fair request. Show me the map of isobars showing the actual gradient extending from Katrina's windshield.

[MiamiensisWx]

There is plenty of damage from Katrina by WIND alone North of Lake Pontchartrain--saying these were from cat 1 or 2 cane is imo patently naive.

I'll buy the pressure gradient argument when I see a documented map showing all of the isobars, hence the actual gradient spread from the storm. Is that available? I have no doubt the size spreads the winds over a larger mass of area, and hence the further from the center the smoother and less intense the change of windspeeds; but unless we can see the actual gradient around the center of circulation through a meaningful map displaying the actual isobars; simply generalizing by stating that size dispells intensity of wind speeds at a low pressure center of circulation is speculation. Someone here has said, show me the Cat. 4 wind damage... a fair request. Show me the map of isobars showing the actual gradient extending from Katrina's windshield.

I was not even saying that particular damage was "only" from Category One or Category Two winds. I was only making a point. Also, Katrina was a Category Four just before landfall, so it is very possible that some sustained Category Four winds reached southeastern and eastern areas of Louisiana before the actual CENTER of Katrina made landfall as a strong Category Three. Have you ever heard of eyewalls touching coastlines before the actual EYE or CENTER makes landfall?

[Pearl River]

CapeVerdeWave said:

I was not even saying that particular damage was "only" from Category One or Category Two winds. I was only making a point. Also, Katrina was a Category Four just before landfall, so it is very possible that some sustained Category Four winds reached southeastern and eastern areas of Louisiana before the actual CENTER of Katrina made landfall as a strong Category Three. Have you ever heard of eyewalls touching coastlines before the actual EYE or CENTER makes landfall?

I can tell you without a doubt, the eyewall winds would not be in St Tammany Parish before the actual center crossed the coast. Too far away from Lower Plaquemines Parish where the center came in.

[Aslkahuna]

Those who want to determine the actual pressure gradient of Katrina can easily do so by going to a site that archives the surface maps from the NWS. They are probably available free if you have access to a site where you can use the .edu domain as your address. The nearest University with a Met Program might even have the maps on archive. That said however, it has long been noted that the edge of the cloud shield of a Tropical Cyclone and the location of the first large outer band as seen by satellite corresponds to a surface pressure isobar that lies in a farily narrow range of pressures. So just by looking at the satellite imagery one can tell that Katrina had a looser gradient than Andrew even though the central pressures were nearly the same. Everyone needs to shake off the idea that there is a hard and fast windspeed relationship to pressures since although some have been derived the data from which they were derived has a lot of scatter. Incidentally, this idea works both ways. In their comprehensive study of STY Paka's passage over Guam, JTWC concluded that although Paka was most assuredly a 130 kt Super when it hit the island, there was no way the pressure could have been at 910 mb at the time but rather closer to the pressure typically found in an ATL storm of the same intensity. They attributed this to the higher ambient pressure surrounding the storm in December. That's another factor to consider. Finally, I think the first GOM storm to exhibit a documented surge out of whack with the landfalling intensity because it was a storm that had weakened rapidly from a high intensity before landfall, was Opal in 1995.

Steve

[Pearl River]

Lets not use a scale anymore. That will settle the whole issue. None was used prior to 1970. The weather service just told people to expect damaging winds and surge. The scale was designed in 1969 and surge was added later. Since a majority of hurricanes weaken before landfall, this scale appears useless and there wouldn't be all this bickering. If a person cannot understand that 130mph wind and 20ft storm can cause major damage, then they shouldn't be living near the coast.

[Aslkahuna]

In reality the scale was not intended for use by the Public nor was the Fujita scale for that matter.

Steve

[Pearl River]

That s fine. It shouldn't be included in the Public Advisory's then.

[P.K.]

Lets not use a scale anymore. That will settle the whole issue.

Well they don't use a scale in the NW Pacific, they just give the wind speed in m/s. It seems to work fine over there.

[Jim Cantore]

The one way to tell how strong she actully was at her initial landfall in Louisana would be to look at damage from Buras and Pilottown which I saw from arial view and didnt look like high end cat 4 damage but this may be due to the sparse buildings in that area

the highest gust measured in Buras was only 114mph

however gusts in Mississippi were near 135

reports like that indicate her strengthening in the few hours between landfalls but satelitte shows diffrently

every conclusion I come to I find something that goes agenist it its just impossible to tell