AWOS cloud base reports

Question

Are cloud base reports on a AWOS given in MSL or AGL?

Answer 1

Cloud bases are given in AGL

Answer 2

AWOS (Automated Weather Observing System), ASOS (Automated Surface Observing Systems) and all surface weather observations are AGL or feet above ground level.

Keep in mind that both AWOS and ASOS use a sensor that points directly overhead and then uses an algorithm to determine coverage.  Think about an overcast layer moving in.  The automated system reports clear skies until the first bit of overcast layer is over the sensor.  At that time the coverage is 'scattered' about to be 'broken', but the system will only register a 'few' clouds.  By the time it is 'broken' to 'overcast' the system will register 'scattered' clouds.

The system is better than no observation at all, but needs to be properly interpreted in order to be safe and useful.

Answer 3

AGL.

However, high altitute reports are usually MSL.

In general, any altitude that happens to be very low will almost always be AGL, while any altitude that is 3000ft or more AGL will tend to be MSL.