Cloud Observations - Ground-based

 


Ground-Based Description of Sky Conditions

Description ASOS (NWS) Human Meaning
Clear (CLR or SKC) 0to 5% 0 No Clouds
Few >5 to <25% 0 to 2/8 Few clouds visible
Scattered (SCT) > 25 to <50% 3/8 to 4/8 Partly cloudy
Broken (BKN) > 50 to <87% 5/8 to 7/8 Mostly cloudy
Overcast (OVC) > 87 to 100% 8/8 Sky is covered by clouds
Sky obscured NA NA Sky is hidden by surface-based phenomena, such as

fog, blowing snow, smoke and so forth, rather than

by cloud cover

table adopted from Meteorology Today by C. Donald Ahrens  1994 West Publishing Company

ASOS - Automated Surface Observing System - uses a ceilometer to automatically measure cloud heights