Download 6. Storms and Severe Weather

Do Now:
What you Know About Hurricanes
1. Describe the background picture
2. Where is the hurricane located?
3. What kind of damage does a hurricane
cause?
Storms and Severe Weather
1.
Mid-latitude Cyclone
2. Hurricane
3. Tornado
Mid-latitude Cyclone
 Along polar fronts of mid-latitudes
 Bring much precipitation in the middle latitudes
 Eventually results in an occluded front
 Associated with thunderstorms, hail and tornadoes
 Figure 7s-3
Thunderstorms
 Formation: Air rises, cools, condenses to form clouds. Strong
updrafts
 Rain, thunder, lightning, strong winds
 Strong downdrafts stop rising air, water vapor present
decreases
Lightning
 Discharge of electricity creating a spark to equalize charges
 Heats the air and expands rapidly producing a loud noise
(thunder)
Tornado
 Smallest, most violent, short lived, haphazard storms
 Rotating column of air, increasing winds and funnel
 Thunderstorm meets high altitude horizontal winds
 Late spring to early summer
 Texas and mid-western US
 Low pressure system
How do we measure a tornado?
The Fujita Scale
 Hurricane Formation
 Super HURRICANES
What exactly is a hurricane?
 A large rotating storm that forms in the tropics and has
winds of at least 119 km/hr (~74 mph)
When is Hurricane Season?
st
1
June
through
November
31st
How are hurricanes structured?
 Rain bands
◦ Rain and wind mild
◦ Pull moisture from ocean
Rain Bands
 Eye
◦ Center of low pressure
◦ Mild wind, no rain
Eye Wall
Eye
 Eye Wall
◦ Winds and rain strongest
◦ Giant thunderstorms
Looking up the eye wall of Hurricane Ivan in the
Gulf of Mexico. (2004)
Hurricane Spiral Animation
 Hurricane Animation
The Recipe for a Hurricane
Supply of warm, moist air
2. Wind rotation via Coriolis Effect
1.

Counterclockwise in N Hemisphere
3. Rotate until maximum speeds are reached
(about 119 km/hr+)
Stage 1
• Tropical Depression
Stage 2
• Tropical Storm
Stage 3
• Hurricane
Hurricane Formation Animation
 http://scifiles.larc.nasa.gov/kids/Problem_Board/problems
/weather/hurricanebasics.swf
What destroys a hurricane?
 Cold water
 Movement over land
How do measure a hurricane?
The effects cont’d
 Storm Surge
 Rapid rise in water level due to high winds
 Most destructive
 E side of hurricane due to winds
 Beach erosion
 Flooding
 Damage to Roads
What can we do to protect ourselves?
 Evacuation plans
 Establish public shelters
 Zoning regulations
 Disaster supplies on hand
 Protecting windows
 Secure loose outdoor items
Hurricane Watches and
Warnings
 Hurricane Watch
 Issued when hurricane expected to arrive within 24-36 hours
 Hurricane Warning
 Issued when hurricane expected to arrive in 24 hours or less