| Stages of development - Hurricane 
            As surface
                pressures continue to drop, a tropical storm
                becomes a hurricane when sustained wind speeds
                exceed 64 knots. A pronounced
                rotation develops around the central core as
                spiral rain bands rotate around the eye of the
                storm. The heaviest
                precipitation and strongest winds are associated
                with the eye wall. |  image adopted from WW2010 Online Guides |