What was Hurricane Ivan at landfall

[gulfcoastdave]

Ok , since we have been beating to death the Camille thing , I decided to take on what Ivanhater posted......... and I agree with him and would like to hear what people have to say on Ivan. Really would like the first hand reports

[wxman57]

You could start your debate by looking at the official post-storm analysis of all the data at landfall and the HRD analysis of the wind swath.

NHC report:
http://www.nhc.noaa.gov/2004ivan.shtml?

Here's the HRD post-storm wind swath analysis. I highlighted the various category winds. Note that I could not find any Cat 3 wind contour in the analysis, but there could have been some pockets of Cat 3 winds over water as the center made landfall. Typically, once the wind field strikes land, surface friction almost immediately drops the winds by 1 or even 2 SS categories. Actually, the winds don't just stop at the coast, the turbulent flow over land lifts the stronger winds up above the surface. Those stronger winds often dip back down to the surface in gusts (winds that last less than 60 seconds).

So the map below doesn't say that there were no Cat 2 or Cat 3 winds inland. It only says that if there were, then they lasted for periods less than 60 seconds at a time. Remember, with hurricanes we only consider the average wind over a 60 second period as a hurricanes "sustained wind".

http://myweb.cableone.net/nolasue/IvanWinds.gif

Now, argue, er, uh, debate away!

[HollynLA]

I clearly remember seeing the scenes from Ivan via helicopter (video on TV) of the coast. It's was completely devestating. Nothing to debate here, Ivan was a storm to remember.

[JonathanBelles]

i'd put ivan as a cat 3 maybe a 2 because of local reports

[Scorpion]

I think that the reason that the NHC keeps some hurricanes artificially strong at landfall(Ivan 130 mph, Katrina 140) is to keep the public on alert, because the sustained winds might have dropped significantly, however the gusts have also increased, so in the end the damage potential might be similar to having a sustained wind of that caliber.

[wxman57]

i'd put ivan as a cat 3 maybe a 2 because of local reports

Can't really rely on any reports inland to estimate its intensity. As per the NHC report, Doppler radar was measuring winds around 6000 ft up at 122 kts. They used a standard conversion to estimate surface winds of 104-108 kts, and then said landfall was 105 kts. But actual observations from the plane with SFMR Doppler radar measured 99kts max sustained winds 6 hours before landfall, and Ivan was definltely weakening as it approached the coast due to dry air entrainment and increasing shear. It's not certain that the plane measured Ivan's peak wind area, so a good estimate would be that Ivan had lower-end Cat 3 winds out over the water as the center reached the coast. The peak sustained wind at Pensacola, 76 kts (85-90 mph) matches very well with the HRD post-storm wind swath analysis. Strongest winds passed west of Pensacola.

Any time a hurricane actually produces sustained hurricane-force winds over land, it's a pretty devastating scene.

[wxman57]

I think that the reason that the NHC keeps some hurricanes artificially strong at landfall(Ivan 130 mph, Katrina 140) is to keep the public on alert, because the sustained winds might have dropped significantly, however the gusts have also increased, so in the end the damage potential might be similar to having a sustained wind of that caliber.

While that's certainly may be true, you have to remember that what the NHC uses to classify a hurricane is MAXIMUM sustained wind, not AVERAGE sustained wind. That maximum will very often be found only over a few sqare miles over water - never over land. The average sustained winds will generally be much lower than the maximum. So you'll never see those max sustained winds at a land observing station.

[Derek Ortt]

At landfall, SFMR only had 95KT winds. This is consistent with the H-Wind analysis as well, indicating a category 2 at landfall, which is what I posted a LONG time ago

[Air Force Met]

While that's certainly may be true, you have to remember that what the NHC uses to classify a hurricane is MAXIMUM sustained wind, not AVERAGE sustained wind. That maximum will very often be found only over a few sqare miles over water - never over land. The average sustained winds will generally be much lower than the maximum. So you'll never see those max sustained winds at a land observing station.

And I think another point...that you brought up in an above post...that people miss is the gust aspect. A gust just isn't some instantaneous wind. It can be...but you may also get a gust to 110 knots that lasts 30 seconds and then the winds drop back down. The overall average for the minute may be SUSTAINED at 85 knots...but a gust up to 110 knots for an extended period of time...just not long enough to make it sustained...will mess you up.

That is where a lot of the confusion comes in, I believe. People say "well I witnessed the damage firsthand...the sustained winds had to be 'X'."

Not necessarily. A prolonged GUST can mess up your world and do just as much damage as if it were sustained. A gust doesn't mean it lasts for a second and goes away...there is a ramp up and down...sometimes it is sudden and the shear force of that shock does the damage.

[Extremeweatherguy]

I think that the reason that the NHC keeps some hurricanes artificially strong at landfall(Ivan 130 mph, Katrina 140) is to keep the public on alert, because the sustained winds might have dropped significantly, however the gusts have also increased, so in the end the damage potential might be similar to having a sustained wind of that caliber.

The NHC actually had Ivan at 120mph for landfall.

[Extremeweatherguy]

I would have to say that Ivan was likely a Cat. 2 at landfall.

[wxman57]

I would have to say that Ivan was likely a Cat. 2 at landfall.

I wouldn't necessarily assume that. Certainly, Ivan's average sustained winds were in the Cat 2 range at landfall, but there was quite probably a small area of Cat 3 winds offshore at landfall.

[Scorpion]

The NHC actually had Ivan at 120mph for landfall.

Operationally it was 130.

[senorpepr]

The NHC actually had Ivan at 120mph for landfall.

Operationally it was 130.

Officially it was 120.

[Ixolib]

Well, if you happened to have a home that got whacked by Ivan's storm surge, it doesn't matter what the "wind speed/category" was. A few pine trees down in one's yard or neighborhood in no way compares to sea water in one's home - even if the pines came through the roof!!. In Camille, we had pines through the roof, and the recovery was really quick - like one or two weeks. In Katrina, however, the results of her storm surge have been in place for months - in my case it was eight months - and will likely be for years to come...

So, a cat five (like Camille ) can create a much lesser impact than a cat two or three (like Katrina & Ivan) - and vice versa, of course. it just depends on which of the two evils (wind or surge) was the lesser.

[Extremeweatherguy]

The NHC actually had Ivan at 120mph for landfall.

Operationally it was 130.

From the NHC report:

Ivan weakened only slowly and made landfall as a 105 kt hurricane

105kts = 121mph

[senorpepr]

Well, if you happened to have a home that got whacked by Ivan's storm surge, it doesn't matter what the "wind speed/category" was. A few pine trees down in one's yard or neighborhood in no way compares to sea water in one's home - even if the pines came through the roof!!. In Camille, we had pines through the roof, and the recovery was really quick - like one or two weeks. In Katrina, however, the results of her storm surge have been in place for months - in my case it was eight months - and will likely be for years to come...

So, a cat five (like Camille ) can create a much lesser impact than a cat two or three (like Katrina & Ivan) - and vice versa, of course. it just depends on which of the two evils (wind or surge) was the lesser.

Very good points. Unforunately, that side of the story tends to be overlooked until the person is in those shoes.

[vbhoutex]

I think that the reason that the NHC keeps some hurricanes artificially strong at landfall(Ivan 130 mph, Katrina 140) is to keep the public on alert, because the sustained winds might have dropped significantly, however the gusts have also increased, so in the end the damage potential might be similar to having a sustained wind of that caliber.

The NHC doesn't do anything artificially. Their reports must be accurate and truthful. Way too much liability otherwise. See wxman57's comments about hurricane winds and how capricious they are. Nothing "artificially strong" about NHC reports though. Totally incorrect statement, imo.

[Scorpion]

The NHC actually had Ivan at 120mph for landfall.

Operationally it was 130.

From the NHC report:

Ivan weakened only slowly and made landfall as a 105 kt hurricane

105kts = 121mph

I meant that in the advisory they stated the landfall was at 130 mph. They changed it to 120 for the best track though.

[TS Zack]

The NHC said it was a Cat 3, then I guess it was a Cat 3. Yes, winds might have been a little less but we didn't have the wind data left along the beach to actually see the sustained winds. The gusts are what cause the damage not the sustained winds. I don't care if its a Cat 1, the gusts will still cause a bunch of damage.