Official NWS Isabel Preliminary Reports

[vbhoutex]

For those who doubt that Isabel was a Category 2 Hurricane this is the official NWS report or at least preliminary report with graphics. The graphics indeed point out very well how a storm can have "different categories(imo)" darn near right next door to each other, at least in the wind category.

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

[wxman57]

vbhoutx, although Isabel probably did reach minimal Cat 2 strength briefly in one small area, the wind reports on that web page don't support Cat 2 strength. But there wast one giant squall that developed right over Cape Hatteras and Okracoke Island. This is the complex that produced the peak gusts to Cat 2 strength.

Here's a good picture that shows the large squall that developed over Cape Hatteras:

ftp://140.208.1.2/pub/mb/al13/Hurricane ... _1000m.jpg

Interestingly, the 2-minute winds were well below hurricane strength at all the recording stations. In the Atlantic Basin, though, a 1-minute average is used for storm classification, so 1-minute winds were most likely higher. The Pacific uses a 10-minute wind average, making it much harder for a storm to be classified as a hurricane. This just goes to show how relatively weak Isabel was. A solid Cat 2 storm would have at least been able to produce hurricane force wind for a mere 2 minutes.

I prepared a talk for a series of hurricane seminars last spring entitled "Hurricane Wind Structure and Inland Wind Decay". Hurricanes tend to have vastly different wind structures. In most cases, the strongest wind is confined to a very small section of the right half of the storm, generally the right-front quadrant. You can see this with Isabel's wind structure at landfall. Note the almost complete lack of 65kt winds left of a north/south line running through the center:

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

And here at landfall, Isabel was probably a Cat 1-2 across Hatteras in the right side of the storm, but the left side had only TS-force winds.

Now, contrast that with Fabian as it approached Bermuda. Note the 90kt winds on the west side of the eye:

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

Remember, a 100kt wind is 4 times as strong as a 50kt wind. You can see that Isabel had a fairly poor wind structure in that hurricane-force winds were confined to a relatively small area.

If you realy want to be scared, take a look at Isabel's wind field when it was a Cat 4 storm:

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

Note the 120 kt (140 mph) wind in all quadrants of the storm. If Isabel had hit NC at that intensity, the coast would have looked like Galveston Island after the 1900 storm. Residents should consider themselves very fortunate that Isabel did not strengthen prior to landfall.

[Lindaloo]

What about the 105 MPH recorded wind in OcraCoke? Is that not CAT 2 winds?

[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

[Forestry1]

115 clocked in Bertie County. My wx station maxes out at 100.00. Here's a link to a RAWS station in Windsor.
<http://www.wrcc.dri.edu/cgi-bin/rawMAIN.pl?ncNGRC>

[Anonymous]

Isabel damage is likely at least 3 billion dollars.

[ncweatherwizard]

115 clocked in Bertie County. My wx station maxes out at 100.00. Here's a link to a RAWS station in Windsor.
<http://www.wrcc.dri.edu/cgi-bin/rawMAIN.pl?ncNGRC>

Interested in knowing how they got those wind speeds. My anemometer in Gates County (which is well exposed to the wind, and easily in the open) read a maximum gust of 65mph, with a maximum sustained wind of 41mph.