What is one of the best visual indications of a thermal?

What is one of the best visual indications of a thermal?

• A. A smooth cumulus cloud with a concave base
• B. A towering cumulonimbus cloud
• C. Clear sky with no clouds
• D. Fog rising from the ground

Answer: (A)

Thermals are updrafts of warm air that lift air parcels and condense moisture as they rise. A visible sign of a thermal is a cumulus cloud that forms where the rising air reaches the dew point and feeds the cloud, typically with a smooth, well-defined base. This cloud indicates a steady, upward column of air providing lift for gliders. A towering cumulonimbus signals strong, convective activity and possible hazards, not a reliable lift source. Clear sky offers no visible lift indicators, and fog rising from the ground shows near-surface moisture rather than sustained aloft updrafts. So a smooth cumulus cloud with a concave (smooth) base best indicates a thermal.

Thermals are updrafts of warm air that lift air parcels and condense moisture as they rise. A visible sign of a thermal is a cumulus cloud that forms where the rising air reaches the dew point and feeds the cloud, typically with a smooth, well-defined base. This cloud indicates a steady, upward column of air providing lift for gliders. A towering cumulonimbus signals strong, convective activity and possible hazards, not a reliable lift source. Clear sky offers no visible lift indicators, and fog rising from the ground shows near-surface moisture rather than sustained aloft updrafts. So a smooth cumulus cloud with a concave (smooth) base best indicates a thermal.