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Thanks to the NSSL &
NOAA for the information following!
Tornadoes are one of
nature's most violent storms. In an average year, about 1,000 tornadoes are
reported across the United States, resulting in 80 deaths and over 1,500
injuries. A tornado is a violently rotating column of air extending from a
thunderstorm to the ground. The most violent tornadoes are capable of tremendous
destruction with wind speeds of 250 mph or more. Damage paths can be in excess
of one mile wide and 50 miles long.
Tornadoes come in all shapes
and sizes and can occur anywhere in the U.S. at any time of the year. In the
southern states, peak tornado season is March through May, while peak months in
the northern states are during the summer.
Thunderstorms develop in warm, moist air in advance of
eastward-moving cold fronts. These thunderstorms often produce large hail,
strong winds, and tornadoes. Tornadoes in the winter and early spring are often
associated with strong, frontal systems that form in the Central States and move
east. Occasionally, large outbreaks of tornadoes occur with this type of weather
pattern. Several states may be affected by numerous severe thunderstorms and
tornadoes.
During the spring in the Central Plains, thunderstorms frequently
develop along a "dryline," which separates very warm, moist air to the
east from hot, dry air to the west. Tornado-producing thunderstorms may form as
the dryline moves east during the afternoon hours.
Along the front range of the Rocky Mountains, in the Texas
panhandle, and in the southern High Plains, thunderstorms frequently form as air
near the ground flows "upslope" toward higher terrain. If other
favorable conditions exist, these thunderstorms can produce tornadoes.
Tornadoes occasionally accompany tropical storms and
hurricanes that move over land. Tornadoes are most common to the right and ahead
of the path of the storm center as it comes onshore.
How Thunderstorms Form:
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 updraft tilts the rotating air from
horizontal to vertical. |
An area of rotation, 2-6 miles wide, now extends through much of the
storm. Most strong and violent tornadoes form within this area of strong
rotation. |
Tornado Myths:
MYTH: Areas near rivers,
lakes, and mountains are safe from tornadoes.
FACT: No place is safe from tornadoes. In
the late 1980's, a tornado swept through Yellowstone National Park leaving a
path of destruction up and down a 10,000 ft. mountain.
MYTH: The low pressure
with a tornado causes buildings to "explode" as the tornado passes
overhead.
FACT: Violent winds and debris slamming into
buildings cause most structural damage.
MYTH:Windows should be
opened before a tornado approaches to equalize pressure and minimize damage.
FACT: Opening windows allows damaging winds
to enter the structure. Leave the windows alone; instead, immediately go to a
safe place
Frequency of Tornadoes
 Tornadoes can occur at any time of the
year.
In the southern states, peak tornado occurrence is in March
through May, while peak months in the northern states are during the summer.
Note, in some states, a secondary tornado maximum occurs in
the fall.
Tornadoes are most likely to occur between 3 and 9 p.m. but
have been known to occur at all hours of the day or night.
The average tornado moves from southwest to northeast, but
tornadoes have been known to move in any direction. The average forward speed is
30 mph but may vary from nearly stationary to 70 mph.
The total number of tornadoes is probably higher than
indicated in the western states. Sparse population reduces the number reported.
STAY INFORMED ABOUT THE STORM
by listening to NOAA Weather Radio, commercial radio, and television for the
latest tornado WATCHES and WARNINGS.
When conditions are favorable for severe weather to develop, a
severe thunderstorm or tornado WATCH is issued.
Weather Service personnel use information from weather radar,
spotters, and other sources to issue severe thunderstorm and tornado WARNINGS
for areas where severe weather is imminent.
Severe thunderstorm warnings are passed to local radio and
television stations and are broadcast over local NOAA Weather Radio stations
serving the warned areas. These warnings are also relayed to local emergency
management and public safety officials who can activate local warning systems to
alert communities.
NOAA WEATHER RADIO IS THE BEST MEANS TO
RECEIVE WARNINGS FROM THE NATIONAL WEATHER SERVICE
The National Weather Service continuously broadcasts updated
weather warnings and forecasts that can be received by NOAA Weather
Radios sold in many stores. The average range is 40 miles, depending on
topography. Your National Weather Service recommends purchasing a radio that has
both a battery backup and a tone-alert feature which automatically alerts you
when a watch or warning is issued.
What To Listen For...
TORNADO WATCH: Tornadoes are possible
in your area. Remain alert for approaching storms.
TORNADO WARNING: A tornado has been
sighted or indicated by weather radar. If a tornado warning is issued for your
area and the sky becomes threatening, move to your pre-designated place of
safety.
SEVERE THUNDERSTORM WATCH: Severe
thunderstorms are possible in your area.
SEVERE THUNDERSTORM WARNING: Severe
thunderstorms are occurring.
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