How can a pilot locate bubble thermals?

• A. Look for birds that are soaring in areas of intermittent heating
• B. Listen for distant thunder
• C. Watch for rain showers in the area
• D. Read the wind direction on the compass

Answer: (A)

Bubble thermals are created where the sun heats patches of the ground, producing rising columns of warm air that a glider can climb in. The most reliable clue that a thermal is present is watching birds that soar, ride, and circle in areas where heating is intermittent. When birds such as raptors encounter a rising column of warm air, they gain altitude by circling in that lift, signaling you to expect a thermal nearby.

Thunder in the distance and rain showers can accompany convection, but they don’t pinpoint where individual thermals are located, and a compass wind direction only tells you how air is moving horizontally, not where the air is rising. So spotting soaring birds in sunlit, patchy heating is the clearest indicator you’re near a bubble thermal.