Objective: SWBAT explain how various storms form WARM UP :

1. Storms: Tornadoes Objective: SWBAT explain how various storms form WARM UP: Using page 46 of the little blue book, DRAW the symbol for each weather front

2. What did you draw?

3. Station Model Practice What DIRECTION is the wind blowing? What WIND SPEED is shown? (use your key from hw sheet) What is the CLOUD COVER?

4. Wild Weather: Storms! • Storm: violent disturbance in the atmosphere • Sudden changes in air pressure • Rapid air movements

5. Storms • Hurricanes • Tornadoes • Blizzards • Thunderstorms • Lake-effect snowstorms (mostly in the Great Lakes Region) • Ice storms

6. Tornadoes

7. Tornado Aviolently rotating column of air (vortex), hanging from a cumulonimbus cloud, with circulation that touches the surface of the earth

8. Tornado Damage Tornadoes mainly cause damage by picking up something and throwing it through the air or hurling objects against something A 20-ton trailer blown off U.S. 30; it bounced 5 times A pick-up truck caught in the path of a tornado

9. The Supercell Tornado forms here

10. Tornadoes form from thunderstormswhich contain one or moreupdrafts(upward moving air which is warmandmoist). These updraftsform towering cumulonimbus cloudswhich race upward and cool to form ice crystals (once they reach the anvilof the thunderstorm). Severe thunderstorms, which is an intense thunderstorm with winds of at least 60mph, most likely produce tornadoes. Tornado 101

11. Tornado Formation

12. Beginning Stage: Tornado begins as a rotating wall cloud which quickly evolves into a funnel

13. Early Stage: Tornado funnel develops (may be transparent) and extends down from the cloud to the ground

14. Mature Stage: Tornado funnel reaches maximum width as well as maximum intensity then begins to shrink

15. Decay Stage: tornado may remain stationary and take on a ropelike appearance before dissipating

16. The Fujita-Pearson Tornado Intensity Scale or F-scale ranks tornadoes by their wind speed. signs of f5 F0- winds 40-72 mph F1- winds 73-112 mph F2- winds 113-157 mph F3 – winds 158-206 mph F4 – winds 207-260 mph F5 – winds > 261 mph Tornado Categories

17. 1. Tornadoes are 400-500 feet wide. Tornadoes have winds around 100 miles per hour. 2. Tornadoes last only a few minutes. 3. Some monster tornadoes are a mile wide, have winds up to 300 mph, last an hour or more, and travel 200 miles. 4. Tornadoes occur most often in the spring (April- June) 5. Most tornadoes in the US occur along “Tornado Alley,” an area that runs from Texas to Illinois. Tornado Facts

18. Where Tornadoes Occur Tornado Alley covers the Great Plains states

19. When Tornadoes Occur • Anytime of the year- usually in the spring, summer, and fall • Most tornadoes occur during late spring in the month of May • Between the late afternoon and early evening is when most tornadoes are spawned • The most dangerous time for formation during evening hours A typical late afternoon tornado

20. Tornado Occurrence by Category

21. F0 Category • (Weak) winds (40-72) mph , little damage • Damage: tree branches snapped, chimneys toppled, signs torn down

22. F3 Category • (Strong) winds: (158-206) mph, severe damage • Damage: most trees uprooted, trains overturned, roofs torn off, walls demolished

23. F5 Category • (Violent) winds: (261- 319) mph, incredible damage; rare Damage: bark peeled off trees, houses lifted off foundations, vehicles travel greater than 100 m through the air

24. Satellite image taken May 3, 1999 @ 645 CDT

26. Other types…Microburst Microbursts are downdrafts from thunderstorms consisting of a narrow column of cool air traveling at high speeds which can cause damage similar to a weak tornado over a small area

27. Other types…Waterspouts A waterspout is a tornado that forms over a body of water, or a tornado that moves from land onto water

28. Signs of a Tornado! • A greenish colored sky associated with the thunderstorm (caused possibly by the scattering of light by particles in the sky) • A sudden drop in barometric pressure • Large hail of at least .75 in. diameter • Strong winds > 60 mph • Frequent and intense lightning • A rotating wall cloud or a cloud that appears to hang from the sky • A loud rumbling noise- seek shelter!

29. Mammatus clouds Green sky

30. Early Warning Systems The National Storm Prediction Center constantly monitors the weather and radars across the U.S. They are responsible for issuing tornado watches and warnings. • Tornado Watch: a parallelogram is drawn around a 10,000 mi.^2 s area where the atmosphere seems to possess the conditions necessary for tornado development (severe thunderstorm) • Tornado warning: a county has a thunderstorm which appears to have produced a tornado or someone has physically spotted a tornado, apparent funnel, or observed damage from what could be a tornado! SEEK SHELTER IMMEDIATELY!!

31. Go to a basement, if you have one. Get in the innermost room of your house. Avoid rooms with windows. Bathrooms are good. Crouch with arms above your head. If outside, lie in a ditch or get under a bridge. If you live in an area with a frequency of tornadoes, listen to forecasts. Witness- Joplin Tornado(start at 23:44) Tornado Precautions

32. Tornadoes Write Time! Why would tornadoes most likely occur late afternoon in warm to moderate temperatures? Explain using the words Heat, Low Pressure, Density, and Rises