Before thunderstorms develop, a change in wind
direction and an increase in wind speed with increasing height
creates an invisible, horizontal spinning effect in the lower
atmosphere. Rising air within the thunderstorm's updraft tilts the
rotating air from horizontal to vertical. Most strong and violent
tornadoes from within this area of rotation.
Photo of thunderstorm, with rotation in the foreground, looking
west. The Rotation is in the area of the lower cloud base. Spotters
refer to this area as a rotating wall cloud. (Woodward, Oklahoma -
Ron Przybylinski)
Moments later, a strong tornado develops within the area of
rotation. Softball-size hail and damaging "straight-line"
winds also accompanied this storm. (Woodward, Oklahoma - Ron
Przybylinski)
'Tornadoes: Nature's Most Violent Storms' was developed by the
National Oceanic and Atmospheric Administration (NOAA)/National Weather
Service (NWS) in cooperation with the American Red Cross and the Federal
Emergency Management Agency (FEMA). It is designed to assist in
heightening public awareness and understanding the dangers associated with
tornadoes. The package provides an introduction to tornadoes and their
impact, discusses tornado development and occurrence, and describes safety
information for homes, schools, places of work, and outdoors. In addition,
basic environmental clues are presented.
Individual use of the pictures within these presentation must have prior
approval from the credited source.