Another type of a subtropical cyclone is a mesoscale low forming in or near an area of horizontal wind shear , also known as a `` dying frontal zone '' , with radius of strongest winds normally less than 30 miles ( 50 kilometers ) . A second type of subtropical cyclone is a mesoscale low originating in or near a frontolyzing zone of horizontal wind shear , also known as a dying frontal zone , with radius of maximum sustained winds generally less than 50 kilometers ( 30 miles ) .