Transcript THUNDERSTORM and TORNADO Formation

THUNDERSTORMS, LIGHTNING and
TORNADOES
FORMATION OF A CUMULONIMBUS
Created by large sections of warm,
moist air rising into cool, dry air.
A cold front or convection in the
atmosphere typically causes the warm
air to rise and water vapor to
condense.
3 stages: cumulus, mature, and
dissipating.
Cumulus Stage
No lightning or chance of tornado
formation during this stage.
Heat from condensing water vapor
in the cloud helps to fuel
expanding and rising air.
The upward-moving air in this
stage can approach speeds of 160
km/hr.
Mature Stage
As the warm moist air mass
rises, the water vapor cools.
The water vapor condenses,
(which releases more heat)
saturates the cloud and
produces torrential rains.
The falling rain pushes and pulls
air downward with it, and the
storm develops regions of fast
moving downdrafts.
Simultaneously, rising warm air
and falling colder air, causes
large amounts of static
electricity to be generated.
Mature Thunderstorms
Large, mature
thunderstorms can…
• Produce precipitation at
astonishing rates, up to
36cm/hr. This causes local
flooding.
• Create hailstones as large as
grapefruits! Ouch!
• Generate tremendous
electrical power and intense
lightning.
• Produce tornadoes with
devastating swirling winds
Dissipating Stage
Downbursts of high speed
wind may occur.
All air within the storm
has become cooler than
the air outside of the
storm.
If deprived of its energy
source of warm, moist air,
the storm soon splits into
a series of disorganized
layers of clouds…and
the storm is finished….
LIGHTNING!
•The rapid movement of electric energy from
one part of a cloud to another or to the
ground.
•Occurs when positive and negative charges
build up in different regions of a
cumulonimbus cloud.
•Large raindrops and hail become charged by
friction as they fall through the cloud.
•The top of the cloud becomes positively
charged.
•The bottom of the cloud becomes negatively
charged
6000 strikes per minute worldwide!
• Lightning is responsible for more deaths
annually than tornadoes and hurricanes
combined.
• It causes fires and is often responsible for
urban blackouts
• Florida has the most in the US. Why?
Lightning is very hot, nearly 5 times as
hot as the surface of the sun!
Thunder is the sound of rapidly
expanding air as it heats to a very high
temperature in a fraction of a second.
A low rumble is caused by
distant lightning.
A sharp crack indicates a nearby
strike.
FLASH……….BOOM!
• Light from a lightning bolt travels very fast
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about 670,000,000 miles/hour
Sound travels much more slowly about
761miles/hour (13 miles/minute or .2
miles/second)
This is why you see the flash before the thunder
is heard.
The smaller the interval between seeing
lightning and hearing the sound of thunder, the
closer you are to the lightning.
What is the approximate distance of a
thunderstorm when you note a 5
second delay between the flash of the
lightning and the sound of the
thunder?
Answer: 5 seconds  .2 miles/second
= 1 mile
Lightning Safety
The six most common dangerous activities associated
with lightning strikes, in order, are:
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Work or play in open fields.
Boating, fishing, and swimming.
Working on heavy farm or road equipment.
Playing golf.
Talking on the telephone.
Repairing or using electrical appliances.
(NWS)
If caught in the open during a strike and the hair on
your head begins to stand on end go inside the
nearest building. If no shelter is available, crouch
down immediately in the lowest possible spot, keep
your feet on the ground. (DO NOT LIE DOWN. )
Treatment for Electrocution by
lightning
• Check breathing and pulse.
• Call 911-send for help
• Perform mouth-to-mouth resuscitation.
• Apply cardiopulmonary resuscitation.
• Only about 10 percent of those struck by
lightning will die.
Warm Up 5/11/12
1. What are some of the factors that cause
thunderstorms?
2. Describe how lightning forms.
3. What type of cloud is responsible for
thunderstorms?
4. If there is 15 seconds between the flash
of light and the crack of the thunder, how
far away is the lightning?
400 Tornadoes in a week!
• Tornadoes are violent winds that rotate
rapidly around an area of low air pressure.
• Called funnel clouds before they reach the
surface of Earth.
• May form during the mature stage of the
most violent thunderstorms.
Cause much damage when their high velocity winds
and twisting motion destroys objects in their path.
Winds may reach 250 mi/hr but often are less than 90
mi/hr.
Tornadoes are seen most often in the central,
Southeastern, and Midwestern parts of the U.S.
Formation of a Tornado by updraft tilting
of wind shear near the ground.
Bibliography
http;//www.nssl.noaa.gov/
National Weather Service- Severe Storms
National Oceanic and Atmospheric Administration
arizonalightning.com- Jacobo Insogna 2002
stormwatch.com 5/8/03
Dan Lloyd Photography -1996
Webshots.com, 5/6/03
University of Akron Ohio
The weather channel
• Write a PARAGRAPH on the formation of
thunderstorms, lightning, and tornados.
– You can include cloud types, factors that
affect each of these, places they occur
most/least, etc.