Tropical Cyclone Return Periods

[bayouwxman]

Can anyone point in the direction of some information on tropical cyclone return periods for the U.S. coastline? Specifically, I'm looking for information on the different methodologies used. I believe Simpson did a study in the 70s that used a threshold of 65 miles...and I seem to remember a study in recent years using slightly different values. Anyone know where I can find details?

[weatherwindow]

historically the 65mi threshold has been something of a standard. i believe it evolved from the use of 65 mi coastal breakpoints used by the nws in defining warning area. another explanations would be the typical distribution of hurricane force winds in a perpendicular landfall....25 mi to the left of the landfall of the geometric center and 40mi to the right of it. however, the individual researcher can define the parameters that he choose to use....and obviously the choice of a closer approach, say 25 miles, to define impact would in turn yeild longer tropical cyclone return periods....similarily, if the parameter is broadened to, say 100 miles, the return period becomes shorter. while i havent seen the study you have referred to, it would be a simple, altho time consuming, task to determine the resultant return period utilizing the unysis/hurdat data(track chronology) to correspond to whatever close approach mileage that you chose to use.....rich

[terstorm1012]

They are statistical averages, to be honest. In addition, as older storms are re-analyzed and upgraded/downgraded, the return periods can change substantially.

When Andrew was upgraded, for example, the return period for Andrew-style storms increased by several decades.

Another example.
In NYC, right now, it's 70 years or so for majors, however that might be longer too since the 1893 storm was not a major hurricane.