On weather maps, half-circles indicate which type of front?

• A. Warm fronts
• B. Cold fronts
• C. Occluded fronts
• D. Stationary fronts

Answer: (B)

Half-circles on weather maps signal a warm front: a boundary where a warm air mass is advancing over a cooler air mass. The semicircles point in the direction the front is moving, showing that warmer air is pushing in. Ahead of the front you often get increasing cloudiness and light to moderate precipitation, and temperatures rise after the front passes. In contrast, cold fronts are shown with triangles, occluded fronts with purple triangles and circles, and stationary fronts with alternating symbols, not just one half-circle symbol.