Not sure what to flair this as, so I just put it as ‘other’
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A picture is probably better than words. In the video below where the warm air is at the ground behind the cool air to the right is a warm front. The cooler air to the left moving in more quickly is a cold front. When the two meet you get an occluded front.
A cold front is when a blob of cold air moves into relatively warmer air: the leading edge is called the front.
A warm front is when a blob of warm air moves into relatively cooler air.
In the mid-latitudes (the continental U.S.) this process driven by areas of low pressure (and the energy of the jet stream); the center is marked by a L on weather maps.
If the low pressure is strong, it will be generating enough wind to move both warm and cold air masses around it in a counter-clockwise direction. Typically the warm air is to the southeast of the center, and the cold, the west.
Sometimes there’s so much cold air back there that it starts to fully wrap around the low pressure center, “outracing” the warm air coming north. This is the occluded front.
Occluded Front
A composite of two fronts, formed as a cold front overtakes a warm or quasi-stationary front. Two types of occlusions can form depending on the relative coldness of the air behind the cold front to the air ahead of the warm or stationary front. A cold occlusion results when the coldest air is behind the cold front and a warm occlusion results when the coldest air is ahead of the warm front.
from https://forecast.weather.gov/glossary.php?letter=o
A warm front is a mass of warm air flowing into a region of cold air.
A cold front is a mass of cold air flowing into a region of warm air.
A stationary front is two masses of warm and cold air sitting next to each other and not moving.
Fronts move in the direction they are pointing, ie it moves towards the semicircles on a warm front or towards the triangles on a cold front. Stationary fronts point both ways since they don’t move, but will indicate the side that the warm/cold air is on.
Fronts generally circle around a high or low pressure system. In the northern hemisphere, high pressure rotates clockwise and low pressure rotates counterclockwise. The reverse is true for the southern hemisphere.
Warm fronts move faster than cold fronts, so it can catch up to a cold front going around the same pressure system and overlap. This is an occluded front. This causes all of the hot air behind the warm front to be lifted up into the air very fast to cool down and lose its moisture in very heavy rainfall.
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