"Stan Prevost" wrote in message
...

The question is really how literally that "reported ground visibility"
rule is used. Is a PIREP acceptable?


No. Ground visibility is determined by sighting objects a known distance
away. A PIREP is just a guess, and many pilots are very bad at guessing
distance.



Are conditions observed five miles
away by a certified human weather observer acceptable?


No.



Can any tower
controller at the field make an acceptable report?


If the controller is the accredited weather observer, then yes. Being
certified to make tower visibility observations is not sufficient.



Is the AWOS/ASOS observation "ground visibility"?


Yes.



Will a METAR report 45 minutes old suffice?


Yes, if it hasn't been superceded by a SPECI.