Here is one formula I found in Bryan Norcross's most recent book, Hurricane Almanac: The Essential Guide to Storms Past, Present, and Future. It is used in Hurricane Re-Analysis.
Sustained Wind (MPH) = 9.615 * (1015 - Central Pressure in Millibars) ^ 0.6143
Another formula is:
Sustained Wind (MPH) = 1375 - (1.315 * Central Pressure in Millibars)
Examples (902 millibars is Katrina's peak at 1800 UTC on August 28, 2005)
9.615 * (1015 - 902) ^ 0.6143 = 175.4 mph
1375 - (1.315 * 902) = 188.9 mph
The first formula is about right and the second formula is off as described in the book, about 10 to 15 mph either way.
Hurricane Almanac: The Essential Guide to Storms Past, Present, and Future
Fletcher's formula... Vmax = 16 * sqrt(Pn - Po)
Vmax: Maximum wind in knots
Pn: Pressure(mb) outer closed isobar
Po: Pressure(mb) minimum central
Examples (902 millibars is Katrina's peak at 1800 UTC on August 28, 2005)
16 * sprt(1015-902) = 170 knots or 195 mph
That's really high right there. Katrina had 175 mph when it was at 902 mb.
Here are maximum extent of hurricane force winds in infamous hurricanes.
Wilma-882 mb 185 mph 50 miles (Maximum extent of hurricane force winds at peak)
Gilbert-888 mb 185 mph 150 miles
Labor Day 1935-892 mb 190 mph 15 miles
Rita-895 mb 180 mph 80 miles
Allen-899 mb 190 mph 120 miles?
Katrina-902 mb 175 mph 105 miles
Camille-905 mb 190 mph 50 miles?
Mitch-905 mb 180 mph 60 miles
Andrew-922 mb 175 mph 30 miles
Charley-941 mb 150 mph 25 miles
Ike-935 mb 145 mph 60 miles (Peak)
Ike-944 mb 100 mph 125 miles (September 11, 2008)
