And purely for reference, but here is the extract from EASA consolidated SERA, effective October 2017:
SERA.9010 Automatic Terminal Information Service (ATIS)
(b) ATIS for arriving and departing aircraft
...
(13) visibility and, when applicable, RVR (*) and, if visibility/RVR sensors related specifically to the sections of runway(s) in use are available and the information is required by operators, the indication of the runway and the section of the runway to which the information refers;
(14) cloud below 1 500 m (5 000 ft) or below the highest minimum sector altitude, whichever is greater; cumulonimbus; if the sky is obscured, vertical visibility when available; (*)
...
(*) These elements are replaced by the term ‘CAVOK’ when the following conditions occur simultaneously at the time of observation: a) visibility, 10 km or more, and the lowest visibility not reported; b) no cloud of operational significance; and c) no weather of significance to aviation.
And from the same document:
‘cloud of operational significance’ means a cloud with the height of cloud base below 1 500 m (5 000 ft) or below the highest minimum sector altitude, whichever is greater, or a cumulonimbus cloud or a towering cumulus cloud at any height.
The term 'weather of significance to aviation' I could not find a definition for within SERA, and wonder how this differs from the previous term. I believe that ICAO Annex 3 defines both terms.
Clear as mud
