1. Storms
Chapter 13

2. Warm-up
Explain the difference between climate and weather.

3. Thunderstorms
Thunderstorm- a brief, heavy storm that consists of rain, strong winds, lightning and thunder

4. Thunder- the sound made by the thermal expansion of air
Lightning- an electric discharge that takes place between two oppositely charged surfaces

5. Thunderstorms 3 conditions necessary for thunderstorms
Lots of moisture in the lower atmosphere
Warmer air begins to rise
Atmosphere must be unstable

6. Stages of a Thunderstorm
Cumulus stage - warm air rises upwards carrying moisture
Mature stage- the precipitation falls rapidly to earth with downdrafts
Dissipation- updrafts slow, storm has no more energy

7. Classifications of Thunderstorms
Classified according to the mechanism that caused the air to rise
Air-mass thunderstorms – unequal heating within one air mass
1. Sea-breeze
2. Orographic lifting
Frontal thunderstorms – advancing cold fronts (strong) and advancing warm fronts (mild).

8. Sea Breeze Thunderstorm

9. Orographic Lifting/Mountain Thunderstorm
Air is forced to rise due to topographic features on the Earth’s surface

10. Frontal Thunderstorms

11. Frontal Thunderstorms
Advancing cold fronts
Severe, forms lines of storms along front
Jet stream can shear off top of cloud forming an anvil shaped cloud
For us, most likely as winter turns into spring

12. Frontal Thunderstorms from advancing cold front

13. Frontal Thunderstorms
Advancing warm fronts not as likely to produce frontal thunderstorms

14. A supercell is a self-sustaining, extremely powerful storm that has intense, rotating updrafts.

15. A downburst is a violent damaging thunderstorm wind concentrated in a local area.

16. Hail
Hail is precipitation in the form of balls or lumps of ice. They form in severe storms. Indicator of tornadoes!

17. Severe Thunderstorm Warnings
A 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

18. Tornado- destructive rotating column of air visible to the naked eye
Tornadoes are classified on the Enhanced Fujita Scale which ranks them according to wind speed, duration, and path of destruction.

19. Tornado Warnings A tornado or funnel cloud has been detected
Take shelter RIGHT AWAY!!!
Get under something sturdy in your basement
No basement? Go to a room that has no windows like a closet or bathroom
In mobile homes, leave them and go to a storm shelter if available or lie flat in a ditch

20. “Tornado Alley” is located in the midwestern US where cP air mases meet mT air masses.
The midwest experiences the most tornadoes in the US

21. April 16, 2011 Tornadoes
2:53pm - EF3 - in the city of Sanford- this is where the Lowe’s was destroyed
Continued NE through Apex and Cary towards Downtown Raleigh at EF1 status
Lots of damage at Shaw University
Continued to N. Raleigh where it hit the mobile home park at 4:05, killing four
Ended near Rolesville at 4:10
On ground for 63 miles

22. <- Lowes in Sanford
Bottom left- houses off Capital Blvd.
Below- Shaw Univ.

23. Path and Strength of Tornadoes

24. Tropical Cyclones
A tropical cyclone is a large, rotating, low-pressure storm formed over warm, ocean water in the summer or fall.
Types of tropical cyclones:
Tropical depression – maximum winds 38 mph or less
Tropical storm – maximum winds mph.
Hurricane/typhoon – maximum winds 74mph or higher.

25. Tropical Cyclones

26. Hurricane- storm over tropical oceans and whose winds are over 120 km/hr and spiral towards a low pressure center
Hurricanes are classified on the Saffir-Simpson scale from 1-5 based on wind speed, air pressure and potential for property damage.

27. Saffir-Simpson Scale

28. Hurricanes
Hurricane watch - hurricane conditions possible within 36 hours.
Begin family's disaster plan, needed supplies, evacuation routes, etc.
Hurricane warning - hurricane force winds expected within 24 hours.

29. Hurricanes The eye is the calm center of the storm.
The eyewall is the wall of storms around the eye. Usually the strongest winds.
The storm surge occurs when hurricane force winds drive water onto land.
Tornadoes and heavy flooding are associated with hurricanes.