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Severe Weather Thunderstorms, Tornadoes, Hurricanes, etc…
 Thunderstorms
Thunderstorms are most often associated with a __________ Cloud
This is a cloud that forms when air is forced high into the atmosphere (against its will)
__________ often create the proper conditions for this to occur
This produces an __________ environment
The processes of cooling, condensing, cloud formation, saturation and precipitation
occur __________
o Thunderstorm Formation
Thunderstorms have three stages…
o ____________________: Warm air rising and condensing to form clouds
o ____________________: Strong updraft of warm, moist air, AND a strong
downdraft of wind and precipitation (hail and lightning can occur in this stage)
o ____________________: The surface has been cooled, cutting off the warm,
moist air that “fuels” the storm. Once the precipitation has fallen from the sky,
the storm is over
o Lightning
Lightning is created by __________ between the rising updraft and the falling downdraft
in a cumulonimbus cloud
This friction creates a _________ (like rubbing your feet across the carpet in your socks)
Eventually there is a discharge between positive and negative charges, creating a
“spark” (like touching a doorknob and getting a shock)
On a larger scale, that “spark” is a ____________________
 Thunder
When lightning strikes, the “bolt” can be as hot as __________ degrees Celsius
The air surrounding that bolt of electricity __________ rapidly (remember… warm air
expands), and then __________ quickly as it cools.
Because of the extremely high temperatures involved, the air expands and contracts
rapidly enough to break the ____________________ (1234 Km/h or 767 mph)
The thunder is a “____________________”
 Wind & Downdrafts
What goes up, must come down!
Thunderstorms are no different, when warm air rises high into the atmosphere, it
eventually cools and comes back down toward the surface
Cumulonimbus clouds can be as tall as __________ m so…
It can fall very quickly toward the surface, producing strong winds (called __________)
 Hail
Moisture gets drawn up so high it __________.
The longer the hail is above the __________ line the bigger it gets.
 Tornadoes
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Violent windstorms that take the form of a rotating column of air, or __________, that
extends downward from a cumulonimbus cloud.
Because of the lower __________ in the center vortex, air near the ground rushes into
the tornado from all directions.
As air streams inward, it is spiraled upward around the core until it eventually merges
with the airflow of the parent __________ deep in a cumulonimbus tower.
Some tornadoes consist of a single __________.
However, within many stronger tornadoes are smaller intense whirls known as suction
vortices that orbit the center of the larger tornado → Multiple Vortex Tornadoes.
o Usually die out in less than a __________.
____________________ are responsible for most of the narrow, short waves of extreme
damage that sometimes are through tornado tracks.
 Most reports of several tornadoes at once actually were ____________________.
 Tornado Development
Less than __________% of thunderstorms produce tornadoes.
Most intense tornadoes are associated with __________ (big, cumulonimbus cloud
structures).
Tornado formation begins with the development of a mesocyclone.
o ___________ - Vertical cylinder of rotating air that develops in the updraft of a
severe thunderstorm.
The mesocyclone within the cloud stretches vertically and narrows horizontally, causing
winds speeds to __________.
Air stretches downward until a portion of the cloud protrudes below the cloud base,
producing a dark, slow rotating ____________________.
 Tornado Classification
Fujita Intensity Scaleo Assesses the __________ produced by a storm as it relates to __________.
 F0- Moderate; __________mph
 F5- Severe; __________mph
Problem: Doesn’t take into account for ____________________ of objects.
The ENHANCED Fujita Scale (EF – Scale) is now used in the US. It DOES take into
account structural damage (but still uses a 0-5 numerical scale)
 Watches & Warnings
____________________- Conditions are ideal for a tornado to be created.
____________________ - An actual tornado has been sighted in the area or is indicated
by weather radar.
Tornado Frequency in the US – Where are most located? __________
Tornado Frequency Around the World – Where are most recorded? __________
 Hurricane Formation
The hurricanes that strike the Caribbean, Gulf of Mexico and the US originate in ______
They begin as ____________________ storm systems over land
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The ____________________ (one of the systems of global winds) blow them out over
the warm water of the Atlantic Ocean
 Hurricane Growth
Remember that low pressure pulls air in at the __________ and pushes it to
____________________ in the atmosphere
Air temperatures at high levels in the atmosphere are __________, and the warm, moist
air over the ocean begins to form clouds (BIG Cumulonimbus clouds)
Lots of ____________________ released during condensation
This creates a very __________ environment
o Continued Growth
Remember that the water over the Atlantic Ocean near Africa is warm (__________)
and has lots of moisture in it (__________ air masses)
As precipitation begins, the rain and cool downdrafts of the Cumulonimbus system are
not enough to cut off the updraft (it’s too warm)
The warm, moist air continues to __________ the system of Cumulonimbus clouds,
making them bigger, and bigger, and bigger
 Hurricane Movement
Once the growing low pressure system is out over the warm water of the Atlantic
Ocean, the Trade Winds blow it to the __________
Because the oceans are relatively __________, there isn’t much to stand in its way and
slow it down
With ____________________ miles of warm ocean water to move across, the system
has plenty of __________ and the __________ to become severe
 Tropical Depressions, Tropical Storms and Hurricanes
A low pressure system (__________) that blows out over the ocean is a
____________________ (a low pressure system is in fact a “depression” of pressure)
If winds in the system reach 39mph, the system becomes classified as a
____________________ (and it is given a name)
If the system continues to gain strength and winds speeds reach 74 mph, it is officially
classified as a __________
 Hurricanes, Typhoons and Cyclones
We give different names to Tropical Storms depending on their __________
Atlantic Ocean - __________
__________ Ocean - Typhoons
Indian Ocean - __________
o They are all basically the same type of storm
 Hurricane Dangers
The most dangerous component of a hurricane is the “__________”
As the storm makes __________, a mound of ocean water (driven by strong winds AND
the “__________” power of the strong low pressure system) is pushed on shore
More people die as a result of __________, than do of strong winds
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 Hurricane Classification
The ____________________ Scale
 A Hurricane’s “Death”
As a hurricane makes landfall, the supply of ____________________ that was fueling it
is cut off
The downdrafts and rain cool the land, decreasing the __________ of the updraft
Without an __________, the system will dissipate and eventually die out (just like a
thunderstorm)
This may take __________ and 100’s of miles
 Hurricane Katrina
In August of 2005, Tropical Storm Katrina developed over the __________
As it approached Florida, it developed into a Category __________ hurricane
It lost some strength over the land (turned back into a ____________________), but
picked right back up when it moved back over the warm water of the Gulf of Mexico
As the storm moved across the Gulf of Mexico, it rapidly developed (from a Category II
to a Category __________ in only 9 hours)
Wind speeds reached __________ mph
A wall of water was pushed toward __________ and __________
 Flooding
The storm surge associated with Katrina was estimated to be _____ feet above sea level
In addition, much of New Orleans is __________ sea level
A systems of _______________ were supposed to protect the city, but this was too high
__________% of the city flooded
 The Aftermath
The most destructive and costliest ____________________ in the history of the US
More than __________ billion dollars in damage
More than __________ people died (__________ still listed as missing)
More than __________square miles declared a Federal Disaster Area
More than __________ million people were left without power