Isabel was NOT a minor hurricane

[JetMaxx]

Based on all available data I've seen thus far (including damage photos and storm surge levels), I believe Isabel was a cat-2 at landfall....with sustained winds in the 85-90 kt range (100-105 mph); gusting to 105-110 kts (120-125 mph).

Peak gusts I'm aware of are 121 mph. The AOML/HRD estimates sustained winds of 91 kt (105 mph) over a small area near Hatteras....and reportedly the 105 mph wind speed from Ocracoke was the limit of the anemometer...a higher value may have occurred -- but it's unknown whether it would have been a sustained wind (1-minute wind).

I'm not ashamed or apologetic for forecasting 120 mph (cat-3) at landfall....the GFDL was progging 120-125 mph; and if I were an NHC forecaster, I'd much prefer to forecast a cat-3 and end up with a cat-2....than the frightening alternative of having residents prepare for a cat-2, only to be surprised by a major hurricane.

I realize the National Hurricane Center has many more data sources and models for forecasting landfall intensity than me....I made my forecast based on the data sources available to me (SHIPS, GFDL, and my knowledge of past hurricanes in that area; and the overall synoptic weather pattern which favored deepening).

PW

[gabrielle01]

Here is latest article from Virginian Pilot online with detailed damage assessment on Outer Banks:
http://home.hamptonroads.com/stories/story.cfm?story=59996&ran=192650

[Guest]

This is perhaps the poorest argument I have ever seen...

so let me see if I have this ...... You claim that isabel was a cat 1
( WTF???.... like 957 MB is cat 1) ) then you cite AOML graphic which clearly puts here as a cat 2--- 91 knots IS Cat2.

am I misisng something here? I mean why would you cite a Graphic that clearly support the cat 2 status of Isabel which is what you are arguing AGAINST?

Have you read what happened in Hatteras?
I'd have to agree with the others questioning the cat designation for this storm.
It was at LEAST solid cat 2...most likely, tho, it was a cat 3.

Will, if you're going to state that Isabel was a solid Cat 2 or more likely a Cat 3 at landfall, then you need to supply some data to validate those claims (measurements by certified/calibrated anemometers or post-storm analysis by structural engineers). The highest sustained wind measurement I've seen is only 80 mph, not 96+ mph. There were 3 recon planes in Isabel prior to landfall, and none measured more than 83 kt surface winds prior to landfall. True, there may be other observations that were a bit higher, and there's no guarantee that the highest wind in that one squall just northeast of the center hit one of the anemometers in its path. Remember, wind gusts do not count toward storm classification. For a storm to be classified a Cat 2 there must be a sustained 96 mph wind that lasts for at least a full minute without dipping below 96 mph. A storm can have sustained wind of 90 mph and gusts to 150, but it's still a Cat 1 by definition.

Certainly, there is no evidence at all that Isabel had SUSTAINED 1-minute winds of Cat 3 strength. Recon didn't measure such winds at any time prior to landfall, and, to my knowledge, not of the numerous recording stations in Isabel's path recored Cat 3 wind for a solid 60 seconds. Wind gusts do not count when classifying hurricanes. But we're generous in the Atlantic basin. In the Pacific, a storm has to maintain a wind speed for 10 minutes to be given a specific wind classification.

But my point wasn't to argue that Isabel was a strong Cat 1 or weak Cat 2 at landfall, the point I wanted to make was that people just do not understand what true 75 mph + winds can do. In so many other instances, the NHC overstates the winds in storms at landfall so much that people have no clue what a 75 mph wind is. Irene in 1999 was an example. It hit Florida as a "Cat 1" storm, but there was never one single observation to support hurricane-force winds.

Here's a graphic of Isabel's winds at landfall, put together by the Hurricane Research division. Note the one small area of 80kt winds that hit Hatteras:

ftp://ftp.aoml.noaa.gov/pub/hrd/hwind/2 ... ol4deg.png

[Derek Ortt]

This was an obvious cat 2. Decent area of cat 2 winds based upon H-Wind analysis from landfall, including a large enough area of 90KT winds, which will likely be the final landfall intensity

[wxman57]

There certainly was a cat 3 storm surge on the outer banks!! You cannot deny that! Perry also brought up an excellent point, Andrew was not named a cat 5 until 10 years later!! It takes more than "official" readings and "official" damage assessment to categorize the storm. You can't have anemometers and dropsonded for every square inch of the storm. You, wxman, are being too absolue about it. You don't even acknowledge the possibilty of later reports validating cat 2 or cat 3 status. It's my personal belief that Isabel was a solid cat 2 storm at landfall, winds sustained near 100 mph. You are not correct yet, and neither am I.. so don't tell anyone that they're wrong. That's yet to be determined..

I agree that we will have to wait for all the data to come in, but current data from the 3 aircraft inside Isabel near landfall and from numerous reporting stations ovewhelmingly suggest that Isabel was nowhere close to a Cat 3 at landfall. And I doubt that 10 years of study will change anything. As for a "Cat 3 storm surge", you have to be more precise. The Saffir-Simpson scale defines a Cat 3 storm surge as (on average) 9-12 feet. A Cat 2 storm typicall produces about 6-8 ft. But storm surge is by no means a constant, it changes according to quite a number of variables (angle of incidence of storm impact, water depth, slope of sea bed, funneling effects into bays, speed of storm movement, etc.).

Certain coastlines produce an enhanced storm surge, even with a weaker storm. For example, a Cat 2 storm hitting the Houston/Galveston area might produce a 6-8 ft storm surge on Galveston Island. But that same storm surge could be nearly TWICE that (up to 15 ft) in northwest Galveston Bay and the Houston ship channel. We saw this effect with Alicia in 1983. Alicia produced about a 12-13 ft storm surge on Galveston, but over 20 ft in northern parts of Galveston Bay. This is most likely what was ovserved in some of the bays/inlets along the NC coast. A Cat 3 storm would have produced considerably higher surge than what was experiended in NC (higher than 12 ft in many inlets). So, you can argue that Isabel produced a storm surge equal to what a Cat 3 storm could produce in some coastal situations, and you would be correct. But I can assure you that a Cat 3 storm hitting Hatteras in the same way that Isabel struck would produce higher than a typical Cat 3 storm surge in many locations.

And you may be correct that Isabel was a minimal Cat 2 storm at landfall, that has yet to be fully determined. But I would not use the term "solid", as any Cat 2 winds were extremely isolated in one squall that happened to hit Hatteras. I would define a "solid" Cat 2 storm as one that has Cat 2 winds around a large part of the center.

I just want you to realize that Isabel was not a very strong hurricane, as hurricanes go. Most residents saw very minimal hurricane force winds (75-85 mph sustained 1-minute wind) or less. A couple of isolated areas may well have observed sustained minimal Cat 2 winds. The highest official observation (and there were many) was 80 mph gusting 105 mph at Okracoke Island. In fact, so far, that was the only sustained hurricane-force wind observed. Now I know I saw several buoys offshore that reported 65kt winds at landfall, so there were other areas hit by hurricane force wind besides Hatteras and Okracoke Island.

Again, my point was not to diminish the impact of this very severe storm. Don't become complacent. Do not be lulled into a false sense of security the next time a hurricane approaches. If the next storm is truely a Cat 3 or Cat 4 hurricane, then you will not want to hang around to find out what REALLY strong wind and high surge is like.

[ncbird]

Those who think Isabel was a bust, or just a little rainstorm... well I'm just too ladylike to tell you what I think, but like Superstorm, I also extend an invitation to my area to come and have a look and tell it to the 50 plus in my county that no longer have homes. Isabel was at least a cat 2 on landfall.... and to tell you the truth I went through hurrican Fran who was a cat 3 and Isabel sure seemed to pack a harder punch.

[wxman57]

Those who think Isabel was a bust, or just a little rainstorm... well I'm just too ladylike to tell you what I think, but like Superstorm, I also extend an invitation to my area to come and have a look and tell it to the 50 plus in my county that no longer have homes. Isabel was at least a cat 2 on landfall.... and to tell you the truth I went through hurrican Fran who was a cat 3 and Isabel sure seemed to pack a harder punch.

Nobody said Isabel was a little rain storm. But you weren't hit by the the worst storm that ever developed, either. At most, Isabel was a weak Cat 2 at landfall, with a poorly-developed hurricane-strength wind field near the center. What you have to understand is that most people who go through a Cat 1 or Cat 2 storm, and even a weaker Cat 3 storm, don't ever really experience sustained 75+ mph winds. This is often the case for the Cape Hattereas area which usually passes through the often much- weaker left half of most hurricanes. This time, you weren't so lucky there and Hatteras did actually see 75 mph sustained wind. I keep trying to drive home the point that it is hard to imagine what 75 mph wind feels like, or the damage it can do. Everyone wants to believe that he or she went through a stronger storm than what was measured, because it's hard to believe what real 75-85 mph winds can do.

I know it's a terrible disaster over there, but don't think by any stretch of the imagination that you went through anything remotely like a major Cat 3 or Cat 4 hurricane, because you didn't.

You mentioned Fran, here's a wind analysis of Fran at landfall:

http://www.aoml.noaa.gov/hrd/Storm_page ... N_88D.html

Note that the winds are in meters/sec. Double the values to get knots and you'll see that Fran had a large area of 80-90 kt winds around the center. Once again, look at Isabel's wind structure at landfall:

ftp://ftp.aoml.noaa.gov/pub/hrd/hwind/2 ... ol2deg.png

Fran was clearly much stronger than Isabel, even though it was just barely a minimal Cat 3 at landfall.

So you can believe what you want about Isabel. Just beware the next Cat 2 or 3 storm that approaches, because it could be a lot worse.

[Derek Ortt]

Cape Hatteras did receive the full brunt of Hurricane Emily in 1993, when they received wind gusts approaching 120KT, with sustained winds approaching 100KT in the western eye wall. However, that system was restricted strictly to the Outer Banks as it never reached the coast. The sounds and VA did not receive the storm, as they did in this instance.

However, due to the angle that Emily impacted the Outer Banks, the surge was from the sounds on the islands, keeping the damage relatively minor as the ocean front property only received a small surge. This time, the ocean surged over the Outer Banks, creating the extensive damage

[TampaFl]

From the Morehead City NWS Priliminary Storm Report. IMHO this will change as time goes onand more information is tabulated. But this might help for this current discussion. Thoughts and comments welcomed.

Robert


http://www.erh.noaa.gov/mhx/HurricaneIsabel.html