The ranking of a hurricane on the Saffir-Simpson scale, used by the U.S. National Weather Service. A somewhat different scale of categories is used for tropical cyclones by the Australian Bureau of Meterology
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}