RELIABLE TORNADO WARNINGS DEPEND ON BOTH TRAINED SPOTTERS AND THE NEW TECHNOLGY

VISUAL ASPECTS

Supercell thunderstorms sometime provide visual clues that they may produce a tornado (left). A lowering and rotating wall cloud signifies the thunderstorm updraft is becoming extremely intense. The occlusion downdraft indicates cool dry air on the storms rear flank may be wrapping around the updraft, a process often critical for tornado development. Cloud striations are another indicator the storm has the deep and persistent rotation necessary for tornadogenesis.

Remember...even if a supercell thunderstorm does not produce a tornado, it is still capable of generating large hail, damaging winds and heavy rains with flash flooding.

Radar Signatures

As a supercell thunderstorm rotates it pulls or wraps the rain and hail in a counterclockwise direction around the storm updraft. This aspect of the storm produces a HOOK ECHO (left) on the radar reflectivity image, a signature sometime indicative of an impending strong or violent tornado.

THE TRAINED SPOTTER IS THE MOST
IMPORTANT SOURCE OF INFORMATION

Many tornadoes do not develop from the top down, but instead from the ground upward. In these situations the radar will provide little or no lead time that a thunderstorm may produce a tornado. Most tornadoes are also of the smaller variety and therefore go undetected by the radar. For example, local weather radar did not provide any evidence of tornado formation when a tornado touched down over Las Cruces in June 20001 (right). Thus the trained spotter remains the most important source of weather information when determining when and where a tornado will strike.

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Photograph of tornado over eastern Las Cruces on June 19, 2001. Courtesy of John Schneider, NASA.