Active cold fronts and returning
warm fronts from the Gulf produce the most adverse weather conditions experienced
in the Pensacola region.
The movement of winter frontal systems through the
area depends on the trajectory of the air mass behind the front, the strength
of the Bermuda High, and the 500 mb flow associated with the frontal system.
Active cold fronts generally begin to reach this area in October and continue
through April, reaching a frequency peak in December and January.
1) If the Bermuda High is in its normal position, another
high that moves down the Mississippi Valley to north Texas, then eastward,
will move the cold front through the local area and well into the Gulf.
During fall, early winter and spring, cold frontal systems
pass through the local area with cloudy conditions persisting for 36-48
hours after the front has passed. A sharp 500 mb trough will accompany
these systems. There will be clearing in the low levels with the passage
of the 850 mb trough. Mid and high cloudiness will remain until the 500
mb flow has veered from a southwesterly to westerly to northwesterly flow.
2) Alternately, cold fronts in the local areas may be
associated with wave development on quasi-stationary frontal systems. This
normally occurs when a wave develops in the southwestern Gulf and moves
northeast. The wave center moves inland usually around Lafayette,
Louisiana. The cold front trails the wave center southwest into the western
Gulf. The low center tracks northeast, and the cold front moves in relation
to the low. Typical cold frontal weather is experienced during passage.
Rapid clearing follows frontal passage.