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An example of a hook echo.
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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.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA