What Happens When a Cold Front Meets a Warm Front? | Sciencing
If the boundary between the cold and warm air masses doesn't move, it is called a stationary front. The boundary where a cold air mass meets a. When a cold air mass meets a warm air mass, a front is formed; if the cold air is replacing the warm air, it is known as a cold front. Cold fronts frequently cause. If hot air approaches a colder air mass, the hot air will rise above the cold air because it's not as dense. When this happens, clouds form from the added moisture.
The other side of the mountain, the leeward side, is generally less lucky. The airflow loses much of its moisture in climbing the windward side. Many mountain ranges virtually squeeze incoming winds like a sponge and, as a result, their leeward sides are home to dry wastes and deserts.
When a warm air mass and a cold air mass collide, you get a front. Remember how low-pressure warm air rises and cold high-pressure air moves into its place? The same reaction happens here, except the two forces slam into each other.
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The cold air forms a wedge underneath the warm air, allowing it to basically ride up into the troposphere on its back and generate rain clouds. There are four main kinds of fronts, classified by airflow momentum. In a warm front, a warm air mass moves into a cold air mass.
This may occur at some locations in the summer. Along the western United States, the Pacific Ocean warms and moistens cold air masses so that the temperature gradient across a cold front is small. Warm Fronts[ edit ] A warm front is found where warm air mass slides over a cold air mass Figure Since the warmer, less dense air is moving over the colder, denser air, the atmosphere is relatively stable. Warm fronts travel much more slowly than cold fronts because the leading cold air mass is dense and sluggish.
Warm air moves forward to take over the position of colder air. Imagine that you are on the ground in the wintertime under a cold winter air mass with a warm front approaching.
The transition between the cold air and the warm air takes place over a long distance.
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This means that the first signs of changing weather appear long before the front is actually over you. In fact, weather changes may appear hundreds of kilometers ahead of the front. Initially, the air is cold: High cirrus clouds mark the transition from one air mass to the other. Illustration of a warm front. Over time, cirrus clouds become thicker and cirrostratus clouds form. As the front approaches, altocumulus and altostratus clouds appear and the sky turns gray.
Since it is winter, snowflakes fall. Soon the clouds thicken and nimbostratus clouds form. Winds grow stronger as the low pressure approaches. As the front gets closer, the cold air mass is just above you but the warm air mass is not too far above that. As the warm air mass approaches, temperatures rise and snow turns to sleet and freezing rain.
Warm and cold air mix at the front, leading to the formation of stratus clouds and fog Figure As the front passes over you, the temperature and dew point rise and the rain likely ends.
The transition is not nearly as dramatic as when a cold front passes over, since there is more mixing of the two air masses occurring in a warm front. The Pacific Ocean also plays a role in modifying the warm fronts that reach the west coast of the United States. These storms are so broad that it is very difficult to spot exactly where the warm front is! Occluded Fronts[ edit ] An occluded front or occlusion usually forms around a low pressure system Figure The occlusion starts when a cold front catches up to a warm front.
The air masses, in order from front to back, are cold, warm, and then cold again. The boundary line, where the two fronts meet, curves towards the pole because of the Coriolis effect. If the air mass that arrives third is colder than either of the first two air masses, that air mass will slip beneath the other two air masses. This is called a cold occlusion.
If the air mass that arrives third is warm, that air mass will ride over the other air mass. This is called a warm occlusion. An occluded front with a warm front being advanced on by a cold front. The order of air masses from front to rear is cold, warm, and then cold.
Occluded fronts can cause drying or storms. Precipitation and shifting winds are typical. The weather is especially fierce right at the occlusion.
When Air Masses Collide | HowStuffWorks
The Pacific coast has frequent occluded fronts. All of these fronts are part of the mid-latitude cyclone. These weather systems will be discussed in the next lesson. Lesson Summary[ edit ] An air mass takes on the temperature and humidity characteristics of the location where it originates. Air masses meet at a front. Stationary fronts become trapped in place and the weather they bring may last for many days. At a cold front, a cold air mass takes the place of a warm air mass and forces the warm air upwards.
The opposite occurs at a warm front, except that the warm air slips above the cold air mass. In an occluded front, a warm front is overtaken by a cold front, which creates variable weather. Review Questions[ edit ] What type of air mass will be created if a batch of air sits over the equatorial Pacific Ocean for a few days? What is the symbol for this type of air mass? What conditions must be present for air to sit over a location long enough to acquire the characteristics of the land or water beneath it?
Discuss how latitude affects the creation of air masses in the tropical, temperate and polar zones. Phoenix, Arizona is a city in the Southwestern desert. Summers are extremely hot. Winter days are often fairly warm but winter nights can be quite chilly.
In December, inversions are quite common. How does an inversion form under these conditions and what are the consequences of an inversion to this sprawling, car-dependent city? Why are the directions fronts move in the Southern Hemisphere a mirror image of the directions they move in the Northern Hemisphere? The size and shape of convection clouds depends on the humidity of the rising air and the strength of the convection.
Convection clouds are made up of millions of suspended water droplets that have condensed from water vapour. But not all convection clouds release rain. Convection clouds are cumulus clouds which can range from the 'fluffy white cotton wool ball' clouds to the towering cumulonimbus thunder clouds.
The fluffy cumulus clouds are known as fair weather clouds.
High School Earth Science/Changing Weather
These rarely produce any rainfall. Larger 'cauliflower-like' cumulus clouds may produce light showers, whilst the cumulonimbus clouds can produce heavy downpours and thunderstorms.
Key points of convection rainfall Sun shines on land and warms the air above it; Warm air rises; Warm air can pick up moisture from water sources seas, lakes etc.Cold Fronts and Warm Fronts
They cannot mix immediately. The lighter warmer air mass begins to rise above the other cooler denser air mass. Fronts are usually several hundred kilometres long and there are three types; warm fronts, cold fronts and occluded fronts.
Types of air masses Air masses may be cold or warm, humid or dry depending on where they originated and from which direction they have come. The British Isles are located at the meeting point of air from many parts of the world.
Warm Fronts Warm fronts occur when light, warm air meets cold air. The warm air rises gradually over the cold air as they meet.