Originally Posted by
Alex Whittingham
ICAO Annex 3 says:
2.2 Use of CAVOK
When the following conditions occur simultaneously at the time of observation:
a) visibility, 10 km or more;
Note.— In local routine and special reports, visibility refers to the value(s) to be reported in accordance with 4.2.4.2 and 4.2.4.3; in METAR and SPECI, visibility refers to the value(s) to be reported in accordance with 4.2.4.4.
b) no cloud below 1 500 m (5 000 ft) or below the highest minimum sector altitude, whichever is greater, and no cumulonimbus;
c) no weather of significance to aviation as given in 4.4.2.3 and 4.4.2.4;
...and our interpretation is that TCu is not CB
Thanks Alex, that clears it up for me!