What causes damp weather?
Dear Mr/Ms B
The term "damp weather" is very subjective...and could mean several
different weather events.
One type of damp weather, and possibly the kind you're thinking of, is
cloudy, foggy days or nights. Fog can form in several different ways, but
the nocturnal fog is the most common, forming as a result of the air near
the surface of the ground cooling sufficiently so the moisture in the air
reaches its condensation point. The next day, once the sun comes up and
warms the earth, the fog dissipates.
Other kinds of damp weather involve precipitation, usually rain, and again,
there are several causes of rain, but they may be grouped into two
categories...convective or stratiform. Convective rains are "showery" types,
including thunderstorms. These rains are usually of relatively short
duration, but may be very intense, producing rainfall rates as high as 4 to
6 inches per hour. Stratiform precipitation is usually less intense, but can
last for longer periods, usually several hours or even a day or more.
I hope this information will help you with your question.
Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO
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Update: June 2012