2. What is a tornado? Tornadoes are relatively small, localized
low- pressure areas associated with powerful thunderstorms under
cumulonimbus clouds. The typical tornado is 820 feet in diameter,
with whirling winds of about 150 miles per hour. The twisting
funnel cloud typically travels at about 40 miles per hour over the
surface. Most tornadoes (but not all!) rotate cyclonically, which
is counterclockwise in the northern hemisphere and clockwise south
of the equator.
3. How are tornadoes formed?
4. In order for a vortex to be classified as a tornado, it must
be in contact with the ground and the cloud base.
5. Main types of tornadoes Rope tornadoes Wide tornadoes
6. Where do tornadoes occur?
7. Tornadoes are most consistently associated with fast-moving
cold fronts that sweep across the midsection of the United States,
drawing warm, moist, tropical air from the Gulf of Mexico. The cold
front is usually associated with a strong low-pressure storm system
that rotates counterclockwise as it swirls across land in the
prevailing westerly wind pattern.
8. Tornadoes can appear from any direction. Most move from
southwest to northeast, or west to east. Some tornadoes have
changed direction amid path, or even backtracked. Hail, any
particular pattern of rain, lightning or calmness, are not reliable
predictors of a tornado threat. Tornadoes can last from several
seconds to more than an hour, however most tornadoes last less than
10 minutes.
9. How is life on Earth affected by Tornadoes?
10. Damage Oklahoma, 2013
11. Some of the damage caused by tornadoes results from the
rapid passage of low pressure. Most houses are built to withstand
downward pressure from much water, snow, or wind against the
structure, especially weight on the roof. When a tornado passes
over a house, however, the low pressure above, countered with high
pressure inside that cannot leak out quickly enough plus wind
pressure under the eaves, causes the house to appear to explode
from within.
12. Solutions to better predict tornadoes
13. The most widely used method worldwide, for over three
decades, was the F-scale developed by Dr. T. Theodore Fujita. In
the U. S., and probably elsewhere within a few years, the new
Enhanced F-scale is becoming the standard for assessing tornado
damage.
14. The National Weather Service usually can predict severe
weather regions several hours in advance, but the exact location of
a tornado must wait for a visual sighting or the occurrence of a
tornado signature on Doppler radar.
15. Balloons carry instrument packages aloft twice a day from
about 90 of the 250 weather stations of the continental United
States.
16. When dangerous storms begin to develop, Doppler radar is
available in most parts of the nation. Doppler radar detects the
wind component parallel to the radar beam, then examines the
pattern of the wind field to find locations of potential
tornadoes.
17. Meteorologists continue to improve their ability to
forecast, locate, and track tornadoes. Space satellites, a
worldwide network of manned weather stations, and sophisticated
computer systems enable meteorologists to see weather as it
develops.