Subtropical cyclone

A subtropical cyclone is a weather system that has some characteristics of a tropical cyclone and some characteristics of an extratropical storm. They can form in a wide latitude band, from the equator to 50°. Subtropical storms can develop into hurricanes, and there is at least one case of a tropical cyclone transforming into a subtropical storm.

These storms can have maximum winds extending further from the center than in a purely tropical cyclone. The maximum recorded wind speed for a subtropical storm is 33 meters/second (74 miles per hour). In the Atlantic Ocean basin, the United States NOAA classifies subtropical cyclones based on maximum sustained surface winds: below 18 meters/second is a subtropical depression, and at or above 18 meters/second is a subtropical storm.

See also: NOAA FAQ on subtropical cyclones (http://www.aoml.noaa.gov/hrd/tcfaq/A5.html)