A large number of cold fronts are associated with the airflow around a mid-latitude cyclone. The flow around a mid-latitude is cyclonic. This is a counterclockwise rotation in the Northern Hemisphere. Due to this direction of rotation, the cold air is brought down on the left side of the mid-latitude cyclone. Cold air moves south behind the cold front. Typically, the cold front is located to the south or southwest of the mid-latitude cyclone before the cold air wraps around the mid-latitude cyclone. The warm front is typically located to the right of the mid-latitude cyclone before it is occluded by the cold front. Typically a cold front approaches from the north, northwest or west. The wind direction behind a cold front will typically be from those directions. This is not the case with a backdoor cold front. A back door cold front is a cold front that approaches from the east or northeast. The winds behind the back door cold front come from those same directions. This type of front can occur when the clockwise rotation around high pressure brings colder air toward the south and west. This type of front can also occur to the north of a developing area of low pressure. The term back door cold front is most commonly used in the northeast U.S. when cool Atlantic maritime air moves in from the east or northeast and replaces warmer continental air. |