Cold front
Topic: Air Masses, Fronts, Cyclones and Thunderstorms · NCERT: Class 11, Ch 9 "Atmospheric Circulation and Weather Systems"
Meaning
A cold front forms where advancing cold air meets warmer air. Cold air is heavier, so it pushes under the warm air like a wedge and lifts it up steeply. The fast-rising warm air builds tall cumulus and cumulonimbus clouds. These give short, heavy showers and thunderstorms. Once the front passes, the temperature drops sharply and the sky clears. On weather maps, a cold front is shown as a line of blue triangles.
Example
In spring, cold fronts often sweep across the Great Plains of the United States. A town may see a line of thunderstorms with heavy rain. A few hours later, it gets cool, clear and breezy weather.
Don't confuse with
- Warm front: here warm air glides gently up over cold air. It gives a long spell of steady rain over a wide area, not short, heavy showers.