Saffir-simpson hurricane scale
From AMS Glossary
Saffir–Simpson hurricane scale
A classification scheme for hurricane intensity based on the maximum surface wind speed and the type and extent of damage done by the storm.
The wind speed categories are as follows: 1) 33–42 m s-1 (65–82 knots); 2) 43–49 m s-1 (83– 95 knots); 3) 50–58 m s-1 (96–113 knots); 4) 59–69 m s-1 (114–134 knots); and 5) 70 m s-1 (135 knots) and higher. These categories are used routinely by weather forecasters in North America to characterize the intensity of hurricanes for the public.