Fronts



A Front is boundary between two different air masses. Fronts are found in troughs of low pressure. Winds tend to converge in the vicinity of fronts leading to clouds and precipitation. Always remember with fronts that cold air rules. The movement of the cold air determines the type of front.

There are many types of fronts, however, we will only discuss four of them.
    1. Cold Front
    2. Warm Front
    3. Stationary Front
    4. Occluded Front

Let's start with some definitions:

1. Cold Front- at a cold front, cold air is displacing the warmer air ahead of the front. Winds associated with cold fronts tend to blow into the front from the cold side of the front. They are depicted on surface maps as blue lines with blue triangles pointing in the direction of warmer air. (See figure)

2. Warm Front- at a warm front, cold air is retreating on the cold side of the front, and is being replaced by warmer air. Warm Fronts are denoted as red lines with red semicircles pointing in the direction of the colder air. (See figure)

3. Stationary Front- this is a type of front that moves very little or doesn’t move at all. It doesn’t move because the winds on the colder side of the front tend to blow parallel to the front. Alternating red semicircles and blue triangles denotes these fronts. Just remember here that the blue triangles always point towards the warmer air. (See figure)

4. Occluded Front- this type of front comes about when the cold front catches up with and overtakes the warm front. The occluded front is depicted on surface maps as being all purple with alternating semicircles and triangles pointing in the direction of movement of the front. (See figure)

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