(usually pronounced ACK-kis) -
Alto
Cumulus
CAStellanus; mid-level clouds (bases generally 8 to 15 thousand feet), of which at least a fraction of their upper parts show
cumulus-type development. These clouds often are taller than they are wide, giving them a turret-shaped appearance. ACCAS clouds are a sign of
instabilityaloft, and may precede the rapid development of thunderstorms.