Interesting Supplementary Vortex

[JetMaxx]

This is a wind profile of hurricane Isabel as the hurricane was centered near Ocracoke....

URNT14 KNHC 181733
SUPPLEMENTARY VORTEX DATA MESSAGE
01336 10773 13960 11111 30038
02338 20771 23934 21111 29028
03340 30770 33906 31210 30039
04342 40768 43863 41210 31048
05344 50766 53795 51212 30041
06346 60765 63748 61611 31030
MF343 M0767 MF058
OBS 01 AT 1628Z
OBS 06 AT 1649Z
OBS 01 SFC WND /////
01351 10762 13710 11514 13034
02353 20760 23754 21412 13060
03355 30758 33798 31212 14118
04357 40757 43866 41010 14106
05359 50755 53920 51110 14094
06362 60755 63957 61010 13090
07365 70757 73989 71008 12094
08368 80757 83013 80907 12081
09371 90758 93033 90907 12075
MF355 M0758 MF118
OBS 01 AT 1657Z
OBS 09 AT 1729Z
OBS 09 SFC WND /////
RMK AF963 2513A ISABEL OB 08


This hurricane may never be officially called a major hurricane at landfall.....but in the pre-1994 doppler radar and eyewall dropsonde days, it would have been. 118 kts (136 mph) equates to 106 kts (122 mph) at the surface...

957 mb and 136 mph flight level winds at landfall....with peak surface winds reported (so far) of 105 mph at Ocracoke and 108 mph near Avon (and I'm certain some higher reports from university researchers and other storm chasers, and private residents will come to light).


Compare these readings to

Hurricane Connie....August 1955
at landfall 962 mb....peak surface wind gust of 105 mph reported from Morehead City, NC

Hurricane Ione....September 1955
at landfall 960 mb...highest surface gust reported was 107 mph at Cherry Point, NC

Hurricane Donna...September 1960
Lowest pressure in North Carolina was 958 mb at Belhaven...estimated between 955-960 mb at landfall east of Wilmington....highest winds in NC reported were unnofficial reports of 80 mph sustained with a gust of 120 mph at Manteo; and official reports of 104 mph at New Bern, 94 mph at Cape Hatteras, and 97 mph at Wilmington.

ALL THREE of these hurricanes are listed by NHC as cat-3 hurricanes at landfall in North Carolina.....Connie, Ione, and Donna...yet recorded winds, central pressure, and tide levels are virtually the same as those of hurricane Isabel.

Anyone can second guess my forecast of 105 kts at landfall if they wish....I don't really care. Based on hurricanes Connie, Ione, and Donna, there is NO DOUBT in my mind that if hurricane Isabel had occurred in 1955, 1960, and probably 1990....it would also have been classified a cat-3 hit on North Carolina....just as they were.


PW

[Mello1]

I noted that the pressure for Isabel was more of a Cat 3 storm then a Cat 2. I like to see how the scientists are going to explain a Cat 2 storm with pressure that low.

[Steve]

Thanks Jet for the analysis and interesting comparisons.

For anyone who's never been to Ocracoke Island, it's amazing. That's an old pirate's hangout with the most sunken ships per capita than anywhere else in the US. You have to take a ferry to get down there, but it's very, very cool.

Steve

[Derek Ortt]

This may not have been classified as a major cane in the early 90's, when the 80 percent rule was used as gospel, even in cases such as Andrew when it was clear that it did not apply. 80 percent of 118KT yields roughly 90-95KT, whihc would have placed it nin the cat 2. Before the early 90's, if we go back to the mid 80's, yes, this woul have been a lead pipe since 3 as anything resembling a 3 was called one, even in cases such as Gloria where it was a weak cat 1

[JetMaxx]

That's right Derek.....in fact, the last "major" hurricane to make a direct hit on Tampa Bay may not have been more than a strong cat-1.

The October 1921 Tarpon Springs-Tampa hurricane had a central pressure of 952 mb at landfall....but the highest recorded wind gusts anywhere near the hurricane were in the 85-95 mph range. Also, the 10' storm tide with a hurricane passing inland NW of Tampa Bay certainly doesn't justify a cat-3 rating (NOT in that area...the October 1873 Punta Rassa cat-3 hurricane produced a 14' storm surge at 959 mb and 100 kts)....yet the 1921 hurricane been "officially" listed as a cat-3 direct hit on Florida since they NHC rating them in the 1970's.

[wxman57]

I've studied a lot of the old "major hurricanes" over the years, and I often wonder about the accuracy of the observations back then. But consider this, since 1995, there have been 31 major hurricanes in the Atlantic basin. No other 9-year period of time has had so many major hurricanes, and these were real Cat 3-4-5 storms, measured by recon with dropwindsondes. Fortunately, only 3 of those major hurricanes have hit the U.S. as major hurricanes. Climatology would suggest about 10 landfalls. But then, perhaps climatology is skewed if we consider the fact that some of the early major hurricanes were really Cat 1 or Cat 2 storms. We'll never know.

Forecasting hurricane intensity is much harder than forecasting the track. Just the smallest change in upper-level winds can reduce a Cat 5 to a Cat 2 in a short period of time. Since we rarely know exactly what the atmosphere is doing to begin with (not much data in the tropics), it's extremely hard to predict the minor changes in upper winds that can lead to weakening or strengthening of a storm. That's why intensity forecasting has not advanced much over the last 30 years.

We still have A LOT to learn, and much more data to acquire for model initialization. Maybe the next generation of sounder-capable satellites can help out.