HF Enhancement

The HF curve is the most current of the "H" series of curves, and is used principally by
weather offices in the western United States.  
It provides good enhancement of low and middle level clouds common
along the Pacific Coast of North America.  Step wedge regions display very cold infrared cloud
top temperatures associated with thunderstorms and frontal systems in 5 degree increments
down to -60 C.  Two additional "repeat gray" segments define cloud top temperatures colder
than -60C.