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What Happens When a Cold Front Overtakes a Warm Front?

The boundary between two masses that consist of different densities and temperatures is a weather front. When the two meet, the warmer air lifts above the cold, dense air. A cold front is the transition area where cold masses of air replace warmer air. The air behind the cold front is drier and colder than the air that is ahead of it.

Movement
- Cold fronts usually move from northwest to southwest, but mountains and large bodies of water can alter the way fronts move, especially when the front is in the lower levels of the atmosphere.
Types
- Four kinds of front occur including stationary fronts, occluded fronts, cold fronts and warm fronts. The type of front that it becomes is determined by the characteristics of the air mass and the direction it is moving in. Rain often accompanies a front and clouds always appear in conjunction with a front, according to Espere.
What Happens
- If a weather front is overhead, you will notice changes in the moisture content of the air, atmospheric pressure, and the direction and speed of the wind. When cold air replaces warm air, this is a cold front. Cold air is behind the warm air; and because cold air is denser than warm air, it strong-arms the warm air out of its way, which makes the warm air rise up.
Cold Versus Warm
- When the warm air rises, it becomes cooler and clouds start to form because the water vapor in the air condenses. Cold air is strong and undercuts the warm air, which makes the warm air rise quickly. This causes thunderstorms and towering clouds. Rain generally comes along with a cold front, but it is short-lived and only affects a small area, but it will be a hard rain.
Effects
- Noticeably cooler air is behind a cold front and drier air is in front of it. A cold front can cause temperatures to drop by 15 degrees in the first hour.
Occluded
- An occluded front occurs when warm, cold and cool air comes together. Whether it is a cold occluded front or a warm occluded front depends on relative states of the cold air masses that are in front of the warm air and behind it. Cold occluded fronts happen when an extremely cold front overcomes a warm front and the cold air lifts the warm front up and the cold front goes underneath. This results in heavy rain and cold weather.
Very Cold Front
- When a cold front overtakes a warm front that is overlying another very cold front, a warm front occurs. Both the warm and cold front move up and over the existing very cold front that stays near the ground.
Stationary
- A stationary front forms when the boundaries between cold air and warm air aren't moving forward.

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