1. Severe Weather: Thunderstorms, Tornadoes, and Hurricanes, oh my!

2. Thunderstorms
Thunderstorms are small, intense weather systems that produce strong winds, heavy rain, lightning, and thunder.
Thunderstorms form from warm moist air and along cold fronts.

3. Recipe for a Thunderstorm
There are three ingredients needed-
The air near the earth’s surface must be warm and moist. It rises or moves upward, which is called an updraft.
The atmosphere must be unstable, meaning the surrounding air is colder than the rising air mass. As the warm air mass rises, it cools and turns into water vapor, condenses and forms CUMULONIMBUS Clouds.

4. As the cloud continues to build, ice particles form near the top of the cloud. As they get large-they form hail. As the hail falls, cold air moves down with it, causing a downdraft.

5. 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 winds

6. 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

7. 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

8. How long is a tornado usually on the ground?
Can range from a few seconds to several hours ...
5 minutes is average
How fast do tornadoes move?
Movement can range from
virtually stationary to more
than 60 miles per hour ...
Average is miles per hour.

9. Watch—means conditions are favorable for tornado to develop
Warning—means that tornado has been spotted

11. MEASURING DESTRUCTION
The Enhanced Fujita Scale rates tornadoes based on the amount and type of wind damage produced.

12. EF-0. Light damage
Wind 65 to 85 mph. Causes some damage to siding and shingles

13. EF-1. Moderate damage Wind 86 to 110 mph. Considerable roof damage
EF-1. Moderate damage Wind 86 to 110 mph. Considerable roof damage. Winds can uproot trees and overturn single-wide mobile homes. Flagpoles bend.

14. EF-2. Considerable damage Wind 111 to 135 mph
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.

15. EF-3. Severe damage Wind 136 to 165 mph. Hardwood trees debarked
EF-3. Severe damage Wind 136 to 165 mph. Hardwood trees debarked. All but small portions of houses destroyed.

16. EF-4. Devastating damage Wind 166 to 200 mph
EF-4. Devastating damage Wind 166 to 200 mph. Complete destruction of well-built residences and large sections of school buildings

17. EF-5. Incredible damage.
Wind 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

19. Location: El Reno, Oklahoma Deaths: 20, including 4 storm chasers
Injuries: 115
Widest tornado ever observed or surveyed – 2.6 miles wide
Intensity – EJ5
Wind Speeds – 296 mph

20. 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

21. Different names are given to hurricanes depending on where they form
Atlantic—we call them hurricanes
Pacific—they are called typhoons
3. Indian Ocean—they are called cyclones

22. Mature hurricanes average about 350 miles across
They have the lowest barometric pressures ever recorded with any storm (905 millibars is lowest recorded)
These huge air pressure differences is what creates the rapid, inward spiraling of winds

23. HURRICANE DEVELOPMENT
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).
2005 Katrina Developing

24. The storm becomes a hurricane when it reaches a wind speed of over 74 mph
Hurricane Formation

25. When a season is very active, Greek letters are used to name tropical storms after the letters of the alphabet had been used.

26. 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.

27. 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

28. CATEGORY WIND SPEED STORM SURGE DAMAGE
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
mph
6-8 feet
Moderate 3
mph
9-12 feet
Extensive 4
mph
13-18
Extreme 5
Greater than 155
Greater than 18
Catastrophic
Video Clip on Wind Tunnel

29. STORM SURGE and FLOODING account for 88% of hurricane-related deaths

30. Category 5 Facts
There have been 33 Category 5 hurricanes on record in the Atlantic since 1924.
Most Category 5 Atlantic hurricanes have occurred in August and September.
Three Atlantic hurricanes have made landfall in the continental U.S. as a Category 5