Transcript Severe Weather - Valhalla High School

Severe Weather
Cyclonic Severe Weather
Cyclonic Severe Weather
 Cyclone=
low pressure system
 Can develop into severe weather if
conditions are right
 Severe weather includes: thunderstorms,
tornado, hurricanes
Hurricanes

Intense Low Pressure System, starts as a tropical low
 Winds peak around 120km/hr
 Storm surge causes most of the damage
 http://www.usatoday.com/graphics/weather/gra/gsurge/fl
ash.htm
 Energy from latent heat released during condensation
fuels the storm
 Spin due to Coriolis Effect
 Lowest pressure is in the center
 Start off the West Coast of South Africa and move
westward across Atlantic Ocean
 Saffir-Simpson Scale catagorizes
Hurricanes – counterclockwise low
pressure systems (lousy weather)
Hurricane Katrina
August 28,2005
Eye Wall (inside) of Hurricane
Katrina (Cat 5)
Hurricane Structure
Anatomy of a Hurricane
Thunderstorms
 Cumulonimbus
clouds
 Thunder/lightening
 Occur along a cold front or in pockets of
rapidly rising air (ocean front)
 Line of thunderstorms is called a Squall
Tornadoes
 Occur
in the spring usually in midwest
region of US (Tornado Alley)
 Move SW to NE
 Fujita Scale rates Tornado severity from
F0-F5 (wind, size)
 Form along cold front from cumulonimbus
clouds (cold air comes off the Rockies and
meets with the warm air from the Gulf of
Mexico)
Fujita Scale
The Enhahanced Fujita Scale
Large Hail Stone
http://www.britannica.com/thunde
rstorms_tornadoes/ocliwea124v4
.html
`
Mesocylone:

A storm-scale region
of rotation, typically
around 2-6 miles in
diameter and often
found in the right rear
flank of a supercell.
Damage-aftermath of F5 Joplin,
MO May 22, 2011 (157 killed)
Aftermath of F5 Joplin, MO
Joplin, Missouri 2011
Joplin, Missouri 2011
Funnel Cloud produced F-5
F-5- Elie, Manitoba 6/22/07
Severe Weather Warnings
 Tornado,
Severe Thunderstorm, and Flash
Flood Warnings
 Severe weather is occurring
 If it is for your area, take shelter right away
 Don’t leave shelter until warning has
expired
Watch vs. Advisory vs. Warning
 Severe
Storm Watch: storm may happen,
conditions are favorable
 Advisory: Storm will be a nuisance (used
for winter storms)
 Severe Storm Warning: storm is going to
occur, and be a danger to others, property,
travel etc…be prepared!
A
Severe Thunderstorm
Warnings
thunderstorm with winds of 58 mph or
greater
 Penny sized hail or larger
 Also contain lots of lightning
 Stay inside
 Keep off the phone
 Don’t take a shower or bath
 Stay away from windows
Lightening



Thunder is the sound of lightening…
Within the thunderstorm
clouds, rising and falling air
causes turbulence which
results in a build up of a
static charge. The negative
charges concentrate in the
base of the cloud.
This first, invisible stroke is
called a step leader.
As soon as the negative and
positive parts (streamer) of
the step leader connect
there is a conductive path
from the cloud to the ground
and the negative charges
rush down it causing the
visible stroke.