1. Hurricanes, Tornadoes, Floods, Droughts, and Fires
OH MY!!!

2. When does hurricane season start?
The Atlantic hurricane season is from June 1 to November 30
The Eastern Pacific hurricane season is from May 15 to November 30

3. Characteristics of a hurricane:
can be up to 600 miles across and have strong winds spiraling inward and upward at speeds of 75 to 200 mph
usually lasts for over a week, moving mph over the open ocean
gather heat and energy through contact with warm ocean waters
rotate in a counter-clockwise direction around an ‘eye’

4. How do hurricanes form?
A hurricane is a system of low pressure that originates over a tropical area.
warm ocean water of 80°F or warmer
rapidly cooling, unstable atmosphere
the wind must be blowing in the same direction and at the same speed to force air upward from the ocean surface
winds flow outward above the storm allowing the air below to rise
hurricanes typically form between 5 to 15 degrees latitude north and south of the equator

5. Hurricane Formation

6. Stages of a hurricane:
Stage 1: Tropical Depression: wind speeds of less than 38 miles per hour
Stage 2: Tropical Storm: wind speeds of 39 mph to 73 mph
Stage 3: Hurricane: wind speeds greater than 74 mph

7. Saffir-Simpson Scale
The Saffir-Simpson Scale has been updated to only reflect wind speed due to the in-accuracies that air pressure and storm surge represent
Although the Saffir-Simpson Scale no longer uses pressure and storm surge it is still a vital component of the tracking and forecast process

8. Tornado Science
A violently rotating column of air extending from a thunderstorm cloud to the ground
In the Northern Hemisphere, tornadoes spin counterclockwise
Important to earth’s weather patterns
1. releases pressure that builds up in the atmosphere
2. the storms that produce them often bring much needed rain

9. EF Scale
Wind Speed (3 sec. gusts)
Description of Damage
EF0
Light Damage
65 – 85 mph
Some damage to siding, shingles and gutters; breaks branches from trees
EF1
Moderate Damage
86 – 110 mph
Considerable roof damage; uproot trees; damage signs; exterior parts of house
EF2
Considerable Damage
111 – 135 mph
Damage to mobile homes; roof damage, uproots large trees; damage to cars, flagpoles, signs
EF3
Severe Damage
136 – 165 mph
Damage to houses, office buildings; ability to toss cars
EF4
Devastating Damage
166 – 200 mph
Completely destroys well-built residences, large public buildings, tosses objects like cars
EF5
Incredible Damage
More than 200 mph
*to date, no EF5s have been recorded
Significant structural damage to mid- and high-rise buildings; throws cars 100 yards or more

10. Tornado Formation
Begins with a front – cool air pushes against warm air in the atmosphere, where the two meet is called a front - cool air presses forward, slides underneath the warm air - warm air is pushed upward, water droplets form - thunderheads (fast-growing clouds) form

11. Tornado Formation
The power of these winds, along with slower winds closer to the ground, can make the rising air start rotating
Air pressure inside the tornadoes funnel is much lower than the air pressure outside which makes it act like a huge vacuum cleaner
The column of spinning winds is called a mesocyclone.

12. Tornado Formation Model

13. Tornado Alley
The geography of central US is suitable to bring all necessary ingredients for a tornado together
More than 500 tornadoes typically occur in this area every year
Tornadoes have been reported in every state

14. Why talk about Floods and Flash Floods?
Floods are among the most frequent and costly natural disasters
Number one killer related to severe weather

15. Flood Science Rainfall intensity and duration
Prolonged rainfall over several days
Intense rainfall over a short time period
Ice or debris jam that causes a river to overflow
Topography, soil conditions and ground cover are also important
Can be slow- or fast-rising

16. Flash Floods Take only a few minutes to a few hours to develop
Can catch people unprepared
Most occur after intense rainfall, after the failure of a dam, or following a sudden release of water

17. What is a drought?
A period of unusually dry weather that persists long enough to cause serious problems such as crop damage and/or water supply shortages.
The severity of the drought depends upon the degree of moisture deficiency, the duration, and the size of the affected area.

18. How do meteorologists predict droughts?
Monitoring variables such as precipitation and soil moisture
These values are compared to previous data to draw conclusions

19. Wild Fire Science Chemical Change: the formation of new material
1. Surface fire - burns along the forest floor (most common)
2. Ground fire – started by lightning, burns along and/or below the forest floor along the dense root systems of trees
3. Crown fire – jumps from treetop to treetop and spreads quickly

21. Why Wild Fires are Important
Natural part of the ecosystem
Cleans out excess vegetation and insects
Wildlife diversity
Eliminates heavy fuel accumulations
Some plants strengthened by fire

22. Fire Behavior Triangle
Fuel
The dryer and lighter the fuels the more easily they will ignite.
A continuous layer of fuels on the forest floor can aid in the spread of a fire.

23. Fire Behavior Triangle
Weather:
(wind, temperature and humidity)
Strong winds may push the flames toward new fuel sources
Winds can transfer embers, sparks or ash to start spot fires
Blowing winds can also dry fuel in moist areas

24. Fire Behavior Triangle
The temperature of fuel will determine how quickly or slowly fuel reaches its ignition point and burns. Moisture dampens fuel and slows the spread of flames.

25. Fire Behavior Triangle
Topography:
Contours, elevation and slope of an area
Barriers within the landscape (rocks, cliffs and water) help determine how a fire will spread