Transcript Thunderstorm PowerPoint - Junction Hill C

Thunderstorms
4 Types of Thunderstorms
Thunderstorms can form
along cold fronts
As cold air advances, the warm
unstable air ahead of the front is
forced upward.
What is a severe thunderstorm?
Thunderstorms can occur anywhere in the world
and at any time of the day. All thunderstorms
produce lightning and thunder. Some have the
potential to produce damaging straight-line winds,
large hail, heavy rain, flooding, and tornadoes.
A thunderstorm is classified as severe when it
contains one or more of the following
phenomena:
Hail 3/4" or greater
Winds gusting in excess of 50 knots (57.5 mph)
A tornado
Dangers of Thunderstorms
Lightning
Floods
Hail
Winds
Tornadoes
Lightning
All thunderstorms
contain lightning.
This photograph
shows lightning
coming from the
side of a
cumulonimbus
cloud.
In most years it is
the thunderstorm's
greatest killer.
Flash Floods
slow-moving
thunderstorms or a
series of storms which
move repeatedly
across the same area
result in flash
flooding. The total
number of flash flood
deaths has exceeded
tornado deaths during
the last 20 years.
Hail
The United States
suffers about one
billion dollars in
crop damage from
hail. Hail rarely kills
people
In China in May,
1986 100 people
were killed, 9,000
injured, and 35,000
homes destroyed
by an intense
hailstorm.
Winds
Thunderstorm winds
also cause
widespread damage
and occasional
fatalities.
Thunderstorm winds
come from raincooled air that falls
with precipitation.
This central Texas
windstorm,
approaching from
the west, was
packing 80 MPH
winds.
Tornadoes
A tornado is a
violently rotating
column of air in
contact with the
ground and out
from a
cumulonimbus
cloud.
Tornadoes are
capable of inflicting
extreme damage.
Tornadoes can be categorized as "weak",
"strong", and "violent"; with weak
tornadoes often having a thin, rope-like
appearance.
About 7 in 10 tornadoes are weak, with
rotating wind speeds no greater than
about 110 MPH.
The typical strong tornado often has a
"classic" funnel-shaped cloud associated
with the whirling updraft. Rotating wind
speeds vary from 110 to 200 MPH.
Nearly 3 in 10
tornadoes are
strong, such
as this twister
on the plains
of North
Dakota
Less than 2 percent of
all tornadoes reach the
200+ MPH violent
category.
Most violent tornadoes
only produce homeleveling damage within
a very small area
Less than 5 percent of
the 5,000 affected
homes in Wichita Falls,
Texas were leveled by
this massive 1979
tornado.
A Tornado Develops