When a prior passes over an area, it way a adjust in the weather. Numerous fronts cause weather events such as rain, thunderstorms, gusty winds, and also tornadoes. In ~ a cold front, there might be dramatic thunderstorms. At a heat front, there may be low stratus clouds. Usually, the skies clear when the front has passed.

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What is a Weather Front?

A weather former is a transition zone between two different air masses in ~ the Earth"s surface. Every air mass has unique temperature and also humidity characteristics. Frequently there is disturbance at a front, which is the borderline whereby two different air masses come together. The disturbance can reason clouds and also storms.

Instead of leading to clouds and also storms, some fronts just reason a readjust in temperature. However, some storm fronts begin Earth"s biggest storms. Tropical waves space fronts that develop in the dry Atlantic s off the coastline of Africa. These fronts can develop into tropical storms or hurricanes if problems allow.

Fronts move across the Earth"s surface over multiple days. The direction of activity is frequently guided through high winds, such as Jet Streams. Landforms choose mountains have the right to also adjust the course of a front.

There are four different species of weather fronts: cold fronts, warmth fronts, stationary fronts, and occluded fronts.

Cold Front


A side check out of a cold front (A, top) and also how the is represented on a weather map (B, bottom).

Credit:Lisa Gardiner

A cold front forms when a cold air mass pushes right into a warmer wait mass. Cold fronts can create dramatic changes in the weather. They relocate fast, up to twice as quick as a heat front. Together a cold front moves right into an area, the heavier (more dense) cool waiting pushes under the lighter (less dense) warm air, bring about it to rise up into the troposphere. Lifted warm air ahead of the front produces cumulus or cumulonimbus clouds and also thunderstorms, favor in the image on the left (A).

As the cold former passes, winds come to be gusty. There is a suddenly drop in temperature, and additionally heavy rain, periodically with hail, thunder, and also lightning. Atmospheric pressure changes from fallout’s to climbing at the front. ~ a cold front moves with your area, you may notice that the temperature is cooler, the rain has stopped, and the cumulus clouds are replaced by stratus and also stratocumulus clouds or clear skies.

On weather maps, a cold former is stood for by a heavy blue line with filled-in triangles along it, choose in the map on the left. The triangles are favor arrowheads pointing in the direction that the prior is moving. An alert on the map the temperatures at the soil level change from warm to cold together you overcome the former line.

Warm Front


A side see of a warmth front (A, top) and also how that is represented on a weather map (B, bottom).

Credit: Lisa Gardiner

A warm front forms when a warm air mass pushes into a cooler wait mass, displayed in the photo to the ideal (A). Heat fronts often lug stormy weather as the warm air mass in ~ the surface ar rises over the cool air mass, do clouds and also storms. Heat fronts move much more slowly 보다 cold fronts because it is more daunting for the warmth air to push the cold, dense air throughout the Earth"s surface. Warm fronts often type on the east side of low-pressure equipment where warmer air from the southern is driven north.

You will regularly see high clouds prefer cirrus, cirrostratus, and middle clouds like altostratus front of a warmth front. This clouds form in the warm air that is high over the cool air. As the former passes end an area, the clouds come to be lower, and rain is likely. There can be thunderstorms roughly the warm front if the wait is unstable.

On weather maps, the surface ar of a heat front is stood for by a heavy red line through red, filled-in semicircles follow me it, choose in the map top top the right (B). The semicircles indicate the direction that the front is moving. They are on the next of the line where the former is moving. Notice on the map the temperatures at ground level space cooler in front of the front 보다 behind it.

Stationary Front


A stationary front is represented on a map by triangle pointing in one direction and also semicircles spicy in the other direction.

Credit:Lisa Gardiner

A stationary front forms when a cold front or warm front stop moving. This happens as soon as two masses of air space pushing against each other, yet neither is an effective enough to move the other. Winds blow parallel to the front rather of perpendicular can help it stay in place.

A stationary front might stay placed for days. If the wind direction changes, the front will start moving again, ending up being either a cold or warm front. Or the front might break apart.

Because a stationary prior marks the boundary in between two air masses, there room often differences in waiting temperature and wind ~ above opposite political parties of it. The weather is often cloudy along a stationary front, and rain or snow regularly falls, specifically if the front is in one area of short atmospheric pressure.

On a weather map, a stationary prior is shown as alternate red semicircles and blue triangles prefer in the picture at the left. Notification how the blue triangles point in one direction, and also the red semicircles point in the contrary direction.

Occluded Front


An occluded former is represented on a weather map through a purple line with alternating triangles and also semicircles.

Credit:Lisa Gardiner

Sometimes a cold front follows right behind a heat front. A heat air mass pushes right into a colder air massive (the heat front), and then one more cold waiting mass pushes into the heat air mass (the cold front). Since cold fronts relocate faster, the cold prior is most likely to overtake the warmth front. This is recognized as an occluded front.

At one occluded front, the cold wait mass native the cold former meets the cool air that was ahead of the heat front. The heat air rises together these waiting masses come together. Occluded fronts usually form around areas of low atmospheric pressure.

There is frequently precipitation along an occluded front native cumulonimbus or nimbostratus clouds. Wind changes direction together the front passes and also the temperature one of two people warms or cools. ~ the front passes, the sky is usually clearer, and also the waiting is drier.

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On a weather map, shown to the left, one occluded prior looks prefer a violet line with alternating triangles and semicircles pointing in the direction that the prior is moving. It end at a low push area shown with a large ‘L’ ~ above the map, starts at the other end when cold and also warm fronts connect.