|KNOWING WHERE A FRONT WILL MOVE
METEOROLOGIST JEFF HABY
A front is a boundary between air masses. Knowing where a front is and where it will move has important forecast implications. The weather
will often be very different on each side of the front. Temperature, dewpoint, wind direction, sky conditions, and precipitation character
can be very different on each side of a front. Frontal position at the surface is monitored through the numerous observation stations that
are located at the surface. The rapidly changing weather conditions on each side of the front is used to locate the frontal boundary.
Fronts have significant variation in the speed of movement and how far they move out of their source region. An important factor that
determines how fast a frontal boundary will move forward is the direction and strength of the middle and upper level winds. The middle
and upper level winds in the troposphere act as a steering mechanism. If they are flowing in the same general direction of a front
then this will help the front move forward and faster. If the middle and upper level flow opposes the motion of the front then a front
can slow down and stall. Another factor is the momentum of air behind a frontal boundary. This momentum can be provided by a strong
or rapidly developing low pressure system. The cyclonic flow associated with a low pressure system will help promote a significant
forward movement of frontal boundaries. When a front moves well away from the parent cyclonic low pressure system then the front will
tend to slow down and stall.
A front has important forecast implications thus it is very important for forecasters to determine the present and future position
of a frontal boundary. Huge variations in weather can occur depending on where the frontal boundary is.