An example of a hook echo.
Click on image for full size
NWSFO/Tuslas, OK
Tornado Forecasts
It's hard to forecast tornadoes. They don't last very long and are also
very complicated. Scientists don't really know how they
form, but they do
where they tend to form. Using what they know about the atmospheric
conditions from past tornadoes, meteorologists can tell when they may
form.
Every twelve hours, meteologists send up weather balloons to take what is
called a
sounding of the atmosphere. The balloons carry
equipment to measure conditions such as atmospheric
stability,
temperature, and humidity.
Using these measurements, forecastors can tell if a tornado is likely to
form. Some of the conditions that are needed are high instability and
high humidity. If these conditions exist, they will issue a
tornado watch.
Using a new kind of
weather radar,
meteorologists can detect a tornado as it's forming--up to 20 minutes
before it touches down! With
conventional radar, they
usually could only detect a tornado only after it had formed. The
tornado would appear as a
hook echo on the
radar return. This also wasn't reliable so forecastors had to rely on
spotter reports. The
new radar gives forecastors the lead time they need to issue a
tornado warning
early enough that the public can seek shelter.
Shop Windows to the Universe Science Store!
The
Fall 2009 issue of The Earth Scientist, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our
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