Hurricanes, Tornadoes, Floods, Droughts, and Fires

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

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

3. 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 10-20 mph over the open ocean • gather heat and energy through contact with warm ocean waters • rotate in a counter-clockwise direction around an ‘eye’ Characteristics of a hurricane:

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

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