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Finding Cold Fronts Using Wind Direction
shift from south-southwest to west-northwest
Cold fronts are not always
identifiable by simply examining the temperature field alone.
Other fields must also be taken into consideration.
For example, below is a surface weather map with an analyzed
low pressure center (red "L") and associated
cold front (blue line) and
warm front (red line).
The numbers are surface
temperature reports and the symbols are
wind barbs,
indicating wind direction and wind speed.
At the time this map was generated,
temperatures ahead of the cold front were in the 50's,
while behind the front, temperatures were only slightly colder
(in the 40's and 50's). However,
notice the change in wind direction (as indicated by the
wind barbs) from one side of the cold front to the
other. Winds ahead of the cold front were generally
from south-southwest, while behind the front, winds had shifted around and
were blowing out of the west. This sudden shift in wind direction was the
key indicator that a cold front was present.
A sudden change in wind direction is commonly observed with the
passage of a cold front.
Before the front arrives, winds ahead of the front (in the warmer
air mass) are typically out of the south-southwest, but
once the front passes through, winds usually shift around
to the west-northwest (in the colder air mass).
definition
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lower dew points
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