Movement of Fronts

Predicting the movement of fronts can be more complex than forecasting the baroclinic low. Fronts may extend for hundreds of miles and not all portions of the front will move at the same speed. 

Continuity/Extrapolation.  The best method to use to predict frontal movement is called the Continuity/ Extrapolation method, which predicts a trend based on the entire history of past movements of the front. The forecast based on this data is that the front will continue to move in the same direction at a steady speed. However, the front will stall or accelerate if the low stalls or acclerates.

Persistence. Persistence is similar to Extrapolation but is less reliable because it only looks at the front's activity in the last two-three hours, rather than the entire history. Because of this, it is good only for short-term forecasting. 

Specific Fronts

Warm Fronts.  Warm fronts most often extend from the northeast through southeast quadrant of a baroclinic low. They generally move toward the northeast at an average speed of 10 knots.  Movement of warm fronts may be difficult to predict because they speed up during the day due to heating and slow down at night due to cooling.  In the day, mixing occurs on both sides of the front, which causes the front to move forward. At night, radiational cooling creates cool dense surface air behind the front. This inhibits both lifting and forward progress. 

Cold Fronts.  Cold fronts most often extend from the southwest quadrant of a low, but may extend from the west or northwest quadrant.  They generally move toward the southeast.  However, depending on the length of the cold front, portions of the front may move toward the east, while other portions move south.  Some sections of the front may move faster than others.

Active cold fronts (slow moving) average 15 knots.  Inactive cold fronts (fast moving) have an average speed of 25 knots.  Although cold fronts generally do not move north, the portion nearest the low may be elongated to move northeast with the baroclinic low’s movement. 

Occluded Fronts.  A newly formed occlusion will initially move at the same speed as the cold front that overtakes the warm front.  Eventually, the occluded front "wraps around" the baroclinic low as the low moves off of the frontal boundary back into the colder air.  The low usually moves to the northwest, on the equatorward side of the occluded front. The position and counterclockwise flow of the low causes the occluded front to "wrap around" the low.  Satellite imagery is the best tool to use for both occlusion identification and any movement of the occlusion.

Concept Mapping Toolkit
Insitute for Human and Machine Cognition
The University of West Florida