Themes > Science > Earth Sciences > Hydrology, Meteorology, Climatology > Meteorology / Climatology > Air Masses, Fronts > Fronts > Cold Front


Transition zone from warm air to cold air

A cold front is defined as the transition zone where a cold air mass is replacing a warmer air mass. Cold fronts generally move from northwest to southeast. The air behind a cold front is noticeably colder and drier than the air ahead of it. When a cold front passes through, temperatures can drop more than 15 degrees within the first hour.

Symbolically, a cold front is represented by a solid line with triangles along the front pointing towards the warmer air and in the direction of movement. On colored weather maps, a cold front is drawn with a solid blue line.

There is typically a noticeable temperature change from one side of a cold front to the other. In the map of surface temperatures below, the station east of the front reported a temperature of 55 degrees Fahrenheit while a short distance behind the front, the temperature decreased to 38 degrees. An abrupt temperature change over a short distance is a good indicator that a front is located somewhere in between.

If colder air is replacing warmer air, then the front should be analyzed as a cold front. On the other hand, if warmer air is replacing cold air, then the front should be analyzed as a warm front. Common characteristics associated with cold fronts have been listed in the table below.

    Before Passing   While Passing   After Passing
Winds   south-southwest   gusty; shifting   west-northwest
Temperature   warm   sudden drop   steadily dropping
Pressure   falling steadily   minimum, then sharp rise   rising steadily
Clouds   increasing: Ci, Cs and Cb   Cb   Cu
Precipitation   short period of showers   heavy rains, sometimes with hail, thunder and lightning   showers then clearing
Visibility   fair to poor in haze   poor, followed by improving   good, except in showers
Dew Point   high; remains steady   sharp drop   lowering
Table adapted from: Ahrens, (1994)


Information provided by: http://weather.about.com