WEATHER WATCH COLUMNS:  AUGUST 2002 ISSUE

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Weather Watch: Gust Fronts

A gust front is the leading edge of the cool downdraft air from a
thunderstorm.  You can recognize the gust front by the abrupt wind
shift, strong winds, and cooler air minutes before the rain from a
thunderstorm begins.  Paddlers should be aware that the rapid
increases in wind speed and wave height, along with the change in wind
direction, may capsize your boat.  To prepare yourself for an
approaching gust front, notice developing thunderstorms in your
vicinity.  Growing cumulus clouds are a good indication of potential
problems.  Once present, the gusty winds can be identified as changes
in the roughness of the water surface.  Try to get off the water
before the gust front arrives, but if you can't, aim your boat into
the thunderstorm winds (and approaching waves) of the gust front.

-David Schultz, NOAA/National Severe Storms Laboratory

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Weather Watch:  Cumulus Clouds

White puffy clouds are called cumulus clouds. If the clouds are
relatively shallow and isolated, then these "fair-weather" cumulus
humilis clouds are not expected to produce any rain.  When cumulus
start growing vertically and the tops look like cauliflower, then
they are called cumulus congestus.  When the tops of cumulus congestus
flatten out and become wispy, they are called cumulonimbus or
thunderstorms.  Cumulus are composed of water droplets, except the
wispy tops which are ice crystals.  This process is called glaciation
and usually represents the beginning of precipitation and lightning
processes inside the storm.

-David Schultz, NOAA/National Severe Storms Laboratory

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