Domanda 139, Meteorology - ATPL - Airline Transport Pilot license

Stable air at mountain top altitude and a wind at least 20 knots blowing across the mountain ridge
Moist unstable air at mountain top and wind of less than 5 knots blowing across the mountain ridge
Either stable or unstable air at mountain top and a wind of at least 30 knots blowing parallel to the mountain ridge
Unstable air at mountain top altitude and a wind at least 20 knots blowing across the mountain ridge