Valkhorn wrote:As to it being a marginal 3, I think it was a strong 3. 125mph is pretty darned closer to 131mph than it is to 111mph.
And, take a look at this graphic:
http://www.srh.noaa.gov/mob/cgi-bin/imageview.php?dir=/0805Katrina&file=vel_2_mob_1359Z.GIFIts at 4,000 feet, if you reduce it by about 5% you get strong category 3 winds well indland, which indicates to me that it was possibly a 4 in terms of wind speeds - considering mobiles radar was a good distance away.
Derek, we did get sustained winds of 100mph in Hattiesburg 90 miles inland, and even a report of 110mph in Laurel, NORTH of us.
So, I'm not sure what you're point is.
Peak winds in a hurricane are typically (certainly not always) around 1500 feet above the ground. The reduction from 1500 ft may be around 70%. From 10,000 ft that reduction is typically 90%. Around 4000 ft, the reducition is probably closer to 80%, not 95%. That would be 130 mph - 26 mph = 104 mph.
There have been a number of "Cat 3" hurricanes making landfall in recent decades that had very tiny areas of Cat 3 winds, if that. Even when a Cat 1 hurriicane makes landfall, very few people actually experience true 75+ mph sustained wind. Those of you here who think you've been through sustained Cat 3 winds in the past may have not even experienced Cat 1 winds. With Ivan - Pensacola appears to have seen Cat 1-2 winds, not Cat 3 winds. Any Cat 3 winds in Ivan passed west of the city.
You also have to remember that the NHC puts the MAXIMUM sustained wind in their advisories, not the average sustained wind in all quadrants of a hurricane. That max sustained wind may be found only in some tiny areas in many cases. Katrina had those max winds over a much larger area, thus the much greater damage compared to an "average" Cat 3.
Katrina had a very low central pressure, but it had such a large core of hurricane-force winds that the pressure gradient was lower than with a typical hurricane. It's the pressure gradient that supports the higher winds, not the pressure itself. Tornadoes can have 200+ mph winds but their central pressure can be relatively high compared to some hurricanes with much lower winds. It's the sharp pressure gradient in a tornado that produces the stronger winds, not the central pressure, itself.
