1. EF5 Tornado Moore, Oklahoma: May 20, 2013 Tornadoes

2. EF5 tornado crossing the Patuxent River near Solomons, MD May 28, 2002

3. Basic questions about tornadoes What is the definition of a tornado? What makes tornadoes visible? What defines tornado intensity? How do tornadoes form? Where do they occur most often? Is tornado frequency increasing? Is there such thing as tornado safety?

4. Some Tornado Links: Storm Prediction Center Tornado History Project http://www.tornadohistoryproject.com http://www.spc.noaa.gov/wcm/

5. Supercell: Long-lived (greater than 1 hour) highly organized convective thunderstorm that is tilted and rotating, often generating tornadoes. Mesocyclone: Supercell detected by Doppler radar. Tornado: Funnel-shaped concentrations of extremely rapidly rotating air (vortices), often emerging from supercells or mesocyclones, visualized by condensation & dust Derecho: Line of fast moving supercells. Tornado Terminology

6. Supercell (Mesocyclone) Wall Cloud (tornado precursor)

7. Tornado Funnels* with Wall Clouds * Funnels are made of condensed water droplets & dust

8. Funnel Shapes

9. Water Spout

10. Dust Sheaths

11. Tornadoes in Urban Environments

12. Tornado Behavior Travel speeds range from almost stationary to more than 90 km/hr. A typical tornado travels around 15-30 km/hr. Doppler radar measured wind speeds in a tornado - strongest was 500 km/hr measured on May 3, 1999 at Moore, Oklahoma. Tornado touchdown time ranges from a few seconds to several hours. The average is about five minutes. Most tornadoes (but not all) in the Northern Hemisphere spin counterclockwise (cyclonic vorticity).

13. Tornado Anatomy

14. Model of a Tornado: the Bathtub Vortex

15. Fujita Tornado Intensity Scale Originally (1970s) F0-F10 (F10=speed of sound in air) Revised in 1990s; allowing more EF5s Tetsuya Fujita

16. Tornado Reports, 1950-2005

17. Tornado Alley

18. Are tornadoes becoming more frequent?

19. Common Sense Tornado Safety Don’tDo Use your basement or stairwell!!

20. Tornado Protection Drill