severe weather: thunderstorms, tornadoes, and hurricanescategory wind speed storm surge damage 1...
TRANSCRIPT
Severe Weather:Tornadoes and Hurricanes
Thunderstorms and Lightning
S6E4 d. Construct an explanation of the
relationship between air pressure, weather
fronts, and air masses and meteorological
events such as tornados and
thunderstorms.
e. Analyze and interpret weather data to
explain the effects of moisture evaporating
from the ocean on weather patterns and
weather events such as hurricanes.
Task:•
• Scenario: You are a team of storm
chasers from the Weather Channel.
Your job is to educate the public
about severe weather as it is
happening. You will need a team of
researchers to do this project.
Each person will play a role, but
you will need to do the research on
the severe storm alone.
Your Task:
• Read each slide then use the
underlined red or underlined
information to fill in your organizer.
As you work think about these
questions :
• What are the “ingredients” for your storm to form?
• How does your storm form?
• What are the atmospheric conditions that are
likely to occur?
• Does your storm form during a specific season or
month(s)?
• Is there a particular location where this storm
forms?
• How does this storm affect the people who live
through it?
• What are some safety tips to survive this storm?
Grab Toto!!
TORNADOES
Are a low pressure storm that usually
forms over land
in an average year, 800 tornadoes are
reported in the U.S.
a tornado is defined as a violently
rotating column of air extending from a
thunderstorm to the ground… the
rotating column of air is called the vortex
the vortex is only visible when debris
and dirt gets carried up with the windsTHE HOOK
Where do they come from?
Tornadoes come from the
energy released in a
thunderstorm.
What makes them
dangerous (as compared to
hurricanes) is that their
energy is concentrated in a
small area, only a hundred
yards across
When & Where do they occur?
Most common east of the
Rocky Mountains and west of
the Appalachian Mountains.
They occur mostly during the
spring and summer (April-June)
They usually occur during the
late afternoon and early
evening.
Usually happen along cold
fronts
How fast do tornadoes
move?
Movement can range
from
virtually stationary to
more
than 60 miles per hour ...
Average is 10-20 miles
per hour.
Watch—means conditions are
likely for tornado to develop
Warning—means that tornado
has been spotted
THE WIND!
• Take a look
at this piece
of wood that
was driven
into the palm
tree.
LOOK
AT
THESE
MEASURING DESTRUCTION
The Enhanced Fujita Scale rates tornadoes based on
the amount and type of wind damage produced.
EF-0. Light damage
Wind 65 to 85 mph. Causes some damage to siding and shingles
EF-1. Moderate damage
Wind 86 to 110 mph. Considerable roof
damage. Winds can uproot trees and
overturn single-wide mobile homes.
Flagpoles bend.
EF-2. Considerable damage
Wind 111 to 135 mph. Most single-wide
mobile homes destroyed. Permanent
homes can shift off foundation. Flagpoles
collapse. Softwood trees debarked.
EF-3. Severe damage
Wind 136 to 165 mph. Hardwood trees
debarked. All but small portions of houses
destroyed.
EF-4. Devastating damage
Wind 166 to 200 mph. Complete
destruction of well-built residences and
large sections of school buildings
EF-5. Incredible damage.Wind +200 mph. Significant structural deformation of
mid- and high rise buildings.
Strong frame houses leveled off foundations and swept
away; automobile-sized missiles fly through the air in
excess of 100 yards
May 25th, 2008
Catastrophic damage was reported in
Parkersburg as much of the town was
destroyed, with reports of flattened
houses and debarked trees. Six
people were killed in Parkersburg and
at least two fatalities were reported
where a housing development was
destroyed. At least 70 people were
injured
At 9:45 p.m. on May 4, 2007, Greensburg was hit by an EF5 tornado. The tornado
was estimated to be 1.7 miles (2.7 km) in width and traveled for nearly 22 miles
(35 km). Ninety-five percent of the city was confirmed to be destroyed, with the
other five percent being severely damaged. The National Weather Service
estimated winds of the tornado to reach 205 mph (330 km/h). This was the first
tornado to ever be rated EF5 since the update of the Fujita scale.
HURRICANES
Low pressure systems that form over warm, tropical
waters near the equator
Most form between 5 and 20 degrees north latitude
— they almost never form in the South Atlantic
They have the lowest barometric pressure
ever recorded with and storm (905 millibars
Is the lowest recorded
These huge areas of low pressure is what creates
The rapid, inward spiraling of winds
When winds have
developed
speeds from 39
to 73 miles per
hour, it is called a
tropical storm
(storms are given
names when
they begin to
have winds of
this speed).
HURRICANE DEVELOPMENT
2005 Katrina Developing
The storm becomes
a hurricane when it
reaches a wind
speed of over 74
mph
Hurricane
Formation
THE END OF A HURRICANE
When a hurricane travels over land or cold water, its
energy source (warm water) is gone and the storm
weakens, quickly dying.
HURRICANE SEASON
•Occurs from June through November
•Most hurricanes form during the late summer
months because the ocean is still retaining heat
from the warmer earlier months
MEASURING DESTRUCTION
We use the Saffir-Simpson scale to rank hurricane
intensities
Saffir-Simpson Scale
CATEGORY WIND SPEED STORM
SURGE
DAMAGE
1 74-95 mph 4-5 feet Minimal
2 96-110 mph 6-8 feet Moderate
3 111-130 mph 9-12 feet Extensive
4 131-155 mph 13-18 Extreme
5 Greater
than 155
Greater
than 18
Catastrophic
Video Clip on Wind Tunnel
STORM SURGE ACCOUNTS FOR 90%
OF
HURRICANE-CAUSED DEATHS
ThunderstormsA storm containing thunder and Lightning
Usually produces heavy wind and
Occasionally hail.
Thunderstorms need:
Moisture
Unstable Air
Lift
Thunderstorm Formation
• Thunderstorms form when warm, humid air rises in an unstable environment.
• A number of things, such as unequal heating of Earth's surface or lifting of warm air along a front can trigger the upward air movement needed to create thunderstorm-producing cumulonimbus clouds.
• Severe thunderstorms produce high winds, damaging hail, flash floods, and tornadoes.
Tornado Precautions
• Go to a basement, if you have one.
• Get in the innermost room of your house. Avoid rooms with windows. Bathrooms are good.
• Crouch with arms above your head.
• If outside, lie in a ditch or get under a bridge.
• If you live in an area with a frequency of tornadoes, listen to forecasts.
Thunderstorm
• Lightning
• Lightning is a charge of
electricity that travels out from
a thunder cloud.
• Like electricity, the bolt of
lightning moves from the
negative to the positive.
• This creates a giant spark.
Have you ever rubbed a
balloon against your hair and
then placed the balloon on the
wall?
As you rub the balloon, it gets
covered with negative charges.
The wall has a positive charge
and the balloon has a negative
charge.
The negative charge is
attracted to the positive charge
and this is why it sticks to the
wall.
Opposites attract!
How is this similar to lightning? Lightning is made in a similar way.
The electricity moves from the negative
towards the positive.
Some parts of clouds end up with a lot of
negative charges (like the balloon).
The earth can have positive charges (like
the wall).
If the difference between the two is big
enough, the negative charge will be
attracted to the positive charge.
A spark will jump between the cloud and
the earth because opposites attract.
Sum Things Up!• Can tornadoes happen anytime or only in
certain times of the year?
• Why do tornados happen most in tornado
alley?
What you should Know…Some low‐pressure systems can give rise to weather events
that are damaging to people, their property, and the land. These
incidents can occur almost anywhere and at any time of the
year. If the conditions are right for a severe storm to occur, the
National Weather Service posts a watch. This means that it is
possible to experience the event that the watch is posted for. If
the storm is sighted and on its way to you, a warning is posted.