You are given a temperature of 25°C and a dew point of 12°C. Estimate the cloud base in feet AGL.

You are given a temperature of 25°C and a dew point of 12°C. Estimate the cloud base in feet AGL.

• A. 5,000 feet
• B. 4,800 feet
• C. 5,200 feet
• D. 5,900 feet

Answer: (C)

The height of the cloud base is set by how far the air must rise and cool to reach its dew point; this is the lifted condensation level (LCL). A handy rule of thumb is that the LCL in meters is approximately 125 times the surface temperature minus the dew point temperature, both in °C. Here the surface temperature is 25°C and the dew point is 12°C, so the difference is 13°C. Multiply by 125 to get about 1625 meters. Convert to feet: 1625 × 3.281 ≈ 5336 ft, which rounds to roughly 5,300 ft. Among the given choices, the closest estimate is about 5,200 ft AGL.

The height of the cloud base is set by how far the air must rise and cool to reach its dew point; this is the lifted condensation level (LCL). A handy rule of thumb is that the LCL in meters is approximately 125 times the surface temperature minus the dew point temperature, both in °C. Here the surface temperature is 25°C and the dew point is 12°C, so the difference is 13°C. Multiply by 125 to get about 1625 meters. Convert to feet: 1625 × 3.281 ≈ 5336 ft, which rounds to roughly 5,300 ft. Among the given choices, the closest estimate is about 5,200 ft AGL.