 Hernan kept Category 4 hurricane intensity a few more days and hurricane strength for six days overall . The hurricane weakened into a tropical storm on July 28 as it moved over cooler waters . Hernan turned more to the west as its low level center became separated from its thunderstorm activity and was steering by a surface high @-@ pressure system to its north . Hernan moved over cooler waters , dissipating as a tropical cyclone early on July 31 . 
