isn't likely to take you to Munchkinland, as it did in "The Wizard of
Oz," but a strong one can destroy buildings and create a damage path a
mile wide. Its wind speeds can top 300 miles per hour.
is a vortex of air rising into a cloud. In their early and mature stages,
all thunderstorms are characterized by rising air, called updrafts. These
updrafts supply the warm, humid air that fuels thunderstorms. But, in some
cases, the column of rising air becomes a vortex – a funnel cloud or
tornado. In a few cases, the vortex becomes a strong tornado with wind
whirling around at speeds close to 300 mph.
develop in warm, moist air in advance of eastward-moving cold fronts. These
thunderstorms often produce large hail, strong winds, and tornadoes.
is a localized, but extremely destructive whirlwind that descends from the
base of a thunderstorm. The twisting vortex extends earthward as a
projecting funnel of powerful winds that sucks up roofs, trees, farmland and
forests. Unlike the gentle transport of Dorothy in the "Wizard of
Oz," these nasty storms can transform a residential area or main
business street into a heap of rubble in just seconds.
Tornadoes are generally formed in a thunderstorm. Thundershowers this
violent require a complex mix of environmental conditions but usually
include: a) very warm, humid air, b) very cool, dry air to the west and
south, c) air to the west trying to replace the warm, moist air (a front
moving in), c) upper level (high in the sky) conditions that first hold down
warmer air from rising and then later, a complete reverse in conditions that
let the warm air rise very fast and very far, and d) an upper level wind
stream to move the air away from the rising column.
is nature's most violent wind. An average of 800 of these vortices spin up
beneath thunderstorms year round in the USA and can generate wind speeds
faster than 250 mph, at times devastating whole communities. The links below
take you to detailed information about the structure, nature and detailed
studies of the tornado.
come from the energy released in a thunderstorm. As powerful as they are,
tornadoes account for only a tiny fraction of the energy in a thunderstorm.
What makes them dangerous is that their energy is concentrated in a small
area, perhaps only a hundred yards across. Not all tornadoes are the same,
of course, and science does not yet completely understand how part of a
thunderstorm's energy sometimes gets focused into something as small as a
Are Tornadoes Measured?
Scale is used to rate the intensity of a tornado by examining the damage
caused by the tornado after it has passed over a man-made structure.
American Meteorology Society's Glossary of Weather and Climate defines
Tornado Alley as: "The area of the United States in which tornadoes are
most frequent. It encompasses the great lowland areas of the Mississippi,
the Ohio, and lower Missouri River Valleys. Although no state is entirely
free of tornadoes, they are most frequent in the Plains area between the
Rocky Mountains and Appalachians."
have hit all fifty states of the United States, but the 30-year average
number of tornadoes per year in Alaska is closer to zero than to one. In
Oklahoma though the average jumps to 52. Although no state is immune for
tornadoes, there is an area that suffers from more tornadoes than any other.
This area is called Tornado Alley.
are most common in "Tornado Alley," shown on the map, particularly
in spring and summer. They're also relatively common in Alabama, Arkansas,
Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Louisiana, Mississippi,
Missouri, Nebraska, Oklahoma, South Dakota, and Texas.
Past and Present
chasers are people who try to get close to storms for the purposes of
observation or science. A couple of chasers have been chasing storms since
the 1940s and 1950s, an amazing feat when you consider how little data was
available for them to figure out where the storms were. Now, many - but not
all - storm chasers travel with laptop computers, anemometers (for measuring
wind), portable weather stations and other equipment, as well as a variety
of video and still cameras.
following WebQuest, you will use the power of teamwork and the abundant
resources on the Internet to learn all about Tornadoes. Each person on your
team will learn one piece of the puzzle and then you will come together to
get a better understanding of the topic. Now, imagine you are in the middle
of a tornado. You are a storm chaser. It is your job to gather information
about the storm for the community. The information you gather helps prevent
injury to people, loss of life, and property damage.
official mascot of the National Weather Service (NOAA) and the Federal
Emergency Management Agency (FEMA).
about the hazards of severe weather which include tornadoes, lightning,
hurricanes, flash floods and winter storms.
are nature’s most violent storms. Tornadoes must always be taken
seriously. Tornadoes can be very dangerous -- sometimes even deadly.