Katrina H-Wind Analysis, marginal 3 at landfall

[mds8309]

I work for a shipyard in Pascagoula and one of the noaa boats recorded a sustain windspeed of 130.

[timNms]

the dropsondes also indicated those wind speeds. I have looked at some of the actual sondes as well

what should be considered is that it does not take a 4 to cause horrific damage

Derek, have you seen the damage first hand? Also, another question for you. When hurricanes are "sampled" by the planes, (for lack of a better word) what are the chances that the lowest pressure and highest wind is not recoreded?
I can't say how bad it was on the coast, because I haven't been there yet. But I can tell you that I've never experienced anything like it before. According to local officials and local mets, Katrina was a cat 3 when she moved across my area and I'm 90 miles north of Gulfport. For her to have done that, either she held herself together really well, or she was more than a 3 at landfall.

[artist]

tim - Derek is just giving us the info - he isn't the one that said it was that.

[Scorpion]

SFMR did say that Jeanne had 112 kt winds. That is very questionable since the damage on the coast wasn't much.

[timNms]

tim - Derek is just giving us the info - he isn't the one that said it was that.

I know. Didn't mean for my post to come off like I was jumping the messenger

[NorthGaWeather]

wind damage seems to correlate well with these results.

Thats because the wind damage that occured was under storm surge.

[NorthGaWeather]

I sure hope some of the destruction goes away here when they officially
downgrade... (that would be cool!)

The damage is real. So are the wind measurements. The required conclusion is that sustained 100 knot winds (or perhaps associated gusts) can cause what people call Cat 4 damage.

The more and more you post about wind damage, the more I realize you know extremely little about it.

[timNms]

wind damage seems to correlate well with these results.

Thats because the wind damage that occured was under storm surge.

Good point. I wonder if anyone has considered this before. 30-35 feet storm surge would definitely cover most buildings and trees...nothing for the wind to blow except the waves lol.

[PTrackerLA]

What is a stratiform hurricane? Rita was referred to as one. All I can say about Rita is that it was a very wet hurricane. I can't imagine what would have happened as far as flooding if she stalled right after landfall.

[Derek Ortt]

the lowest pressure is recorded by the aircraft since they stay in the eye for about 3-5 minutes until they find the lowest pressure, then they drop the dropsonde at that point

As for the winds, I believe the onboard doppler does a good job, plus, they drop many sondes in the eye wall

[Dave C]

PTracker LA Stratiform means there not much convective cloud tops with Rita, it was more low level clouds which also means less intense winds to mix down from aloft. The west side of Katrina was like that, it still had rain bands on it's west side but the clouds were mainly low-level(little convection).

[caneflyer]

the lowest pressure is recorded by the aircraft since they stay in the eye for about 3-5 minutes until they find the lowest pressure, then they drop the dropsonde at that point

Well, that's not quite true. The aircraft flies more or less directly across the center, flying perpendicular to the wind direction. The crew is looking for the wind center, not the pressure center. When the winds shift roughly 180 degrees, this marks the fix location and the drop is made. Sometimes, the plane misses the wind center by a few miles and so the drop is made at the sharpest wind shift, even if it is not a full 180 degrees.

If the wind and pressure centers in the eye are not co-located, the drop pressure will be a little bit higher than the storm's minimum pressure. Similarly, the drop moves with the wind in the eye, and it will often rotate around and drift towards the eyewall. It is important to look at the winds near the surface of an eye sounding to see how close to the actual center it got.

[fasterdisaster]

Right...a marginal 3 at Louisiana landfall or Mississippi landfall? Because either way, I think I agree with the poster who said BS because there were sustained winds that would NOT have happened in a marginal Category 3 hurricane.

[Derek Ortt]

the NOAA plane did NOT fly directly across the center. They made turns and the like and spent far longer than normal inside of the eye, until they marked the center at flight level. During that time, the on board screens would show the pressure oscillating between a 5mb range

The one drop on the flight recorded a 912mb with very light winds at the surface. They usually are good about keeping it in the eye

[f5]

i don't think a CAT 3 is able to produce a 35 ft storm surge

[Brent]

i don't think a CAT 3 is able to produce a 35 ft storm surge

It had a Cat 5 surge because it was a Cat 5 12 hours before landfall.

The surge does NOT come down because the winds do.

[f5]

i don't think a CAT 3 is able to produce a 35 ft storm surge

It had a Cat 5 surge because it was a Cat 5 12 hours before landfall.

The surge does NOT come down because the winds do.

People need to learn the tsunami lesson beacuse the hurricane weakens does not mean the surge does the same way a tsunami doesn't weaken long after the earthquake is over.

[Brent]

i don't think a CAT 3 is able to produce a 35 ft storm surge

It had a Cat 5 surge because it was a Cat 5 12 hours before landfall.

The surge does NOT come down because the winds do.

People need to learn the tsunami lesson beacuse the hurricane weakens does not mean the surge does the same way a tsunami doesn't weaken long after the earthquake is over.

That was exactly my point.

[Ixolib]

It had a Cat 5 surge because it was a Cat 5 12 hours before landfall.

The surge does NOT come down because the winds do.

And it is exactly THIS point that I hope the NHC, TWC, local authorities and whoever else will take very seriously and begin educating and re-educating the coastlal public on this phenomena.

So far, it seems to me that the only storms in "recent" history that have brought with them cat 5 surges while making landfall as only 3's or 4's were Ivan, Katrina, and Rita. This whole "surge" potential issue has GOT to get more press, and hence, more education. Discovery Channel, History Channel, National Geographic - this would be a great topic for any or all of them!!

[jasons2k]

It had a Cat 5 surge because it was a Cat 5 12 hours before landfall.

The surge does NOT come down because the winds do.

And it is exactly THIS point that I hope the NHC, TWC, local authorities and whoever else will take very seriously and begin educating and re-educating the coastlal public on this phenomena.

So far, it seems to me that the only storms in "recent" history that have brought with them cat 5 surges while making landfall as only 3's or 4's were Ivan, Katrina, and Rita. This whole "surge" potential issue has GOT to get more press, and hence, more education. Discovery Channel, History Channel, National Geographic - this would be a great topic for any or all of them!!

Exactly - and all 3 storms have 3 things in common: 1) They were Cat. 5s prior to landfall 2) they did not make landfall as a Cat. 5 and 3) They made landfall on the northern Gulf Coast where the shelf extends further out.