Tornadoes. Be able to define what a tornado is. Be able to list several facts about tornadoes.

Transcription

1 Tornadoes Be able to define what a tornado is. Be able to list several facts about tornadoes.

2 1. Where do tornadoes most U.S. is # 1 occur in the world? Tornadoes are most common in Tornado Alley.

3 Tornado Facts tornadoes spin up beneath T-Storms each year in the U.S. 1,253 tornadoes per year in the U.S. 3. Typically kill about people 4. Tornadoes are violently rotating columns of air attached to a thunderstorm and in contact with the ground, whether or not a condensation funnel is visible to the ground. Stronger pressure gradient than a hurricane.

4 2013 Tornado Data

5 5. Where have tornadoes occurred? Tornadoes have occurred: In all 50 States On all continents except Antarctica

6 6a. When do most tornadoes occur? April to July During late spring to early summer.

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8 6b. When do most tornadoes occur? 2 pm to 8 pm During afternoon and evening hours

9 7. What forward speed do tornadoes move at? The average forward speed is 30mph but may vary from nearly stationary to 70mph

10 8. Where does a tornado come from? It s called a funnel cloud until it makes contact with the ground. A cloud that protrudes below the cloud base is called the wall cloud. Updraft of the storm

11 9. How do Tornadoes look? Tornadoes take different forms, some are large and ominous, while others are relatively small and may be difficult to see.

12 Tornado Variations in Appearance Pencil-shaped tornado about the time of F5 damage near Union City, OK, May 24,1973.

13 Tornado Variations in Appearance Cone-shaped tornado with debris fan south of Hill City, KS, looking west, June 9, 2005.

14 Tornado Variations in Appearance Wedge tornado, where the visible funnel is wider than the distance from ground to surrounding cloud base, looking northwest near Argonia, KS, May 29, 2004.

15 10. What is a Waterspout Waterspouts are tornadoes that occur over water. Two types of water spouts Type A waterspout forms in thunderstorm and travels over water (More violent) Type B waterspout forms from building cumulus clouds (less violent) If this forms on land it is called a landspout

16 Tornado Tracks

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19 11. Tornadoes usually move in which direction? Tornadoes can appear from any direction. Most move from southwest to northeast. Most tornadoes -- but not all! -- rotate cyclonically, (which is counterclockwise in the N.H.)

20 12. What scale is used to measure tornado strength? Fujita Scale Because tornado winds cannot be measured directly, a rating on the Fujita scale is determined by assessing the worst damage produced by the storm.

21 Fujita Scale F0 (40-72 mph) Light damage. Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged. F1 ( mph) Moderate damage. The lower limit is the beginning of hurricane wind speed; surface peeled off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads. F2 ( mph) Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light-object missiles generated. F3 ( mph) Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off ground and thrown. F4 ( mph) Devastating damage. Well-constructed houses leveled; structures with weak foundations blown some distance; cars thrown and large missiles generated. F5 ( mph) Incredible damage. Strong frame houses lifted off foundations and carried considerable distances; automobile sized missiles thrown through the air in excess of 100 yd (equivalent to 91 m); trees debarked.

22 13. How do Tornadoes Form? Need Wind Shear A change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere. Rising air within the thunderstorm's updraft tilts the rotating air from horizontal to vertical.

23 Tornado Formation

24 Weak Tornadoes F0-F1 69% of all tornadoes Less than 5% of tornado deaths Lifetime minutes Winds less than 110 mph

25 Strong Tornadoes F2-F3 29% of all tornadoes Nearly 30% of all tornado deaths May last 20 minutes or longer Winds mph

26 Violent Tornadoes F4-F5 Only 2% of all tornadoes 70% of all tornado deaths Lifetime can exceed 1 hour Winds greater than 205 mph

27 Environmental Clues Tornadoes are often preceded by a dark, often greenish sky, large hail, and often a loud roar, similar to a freight train. Most strong and violent tornadoes occur with "supercell" thunderstorms.

28 Remember Other Threats In addition to tornadoes, thunderstorms often produce other hazards. Flash Floods/Floods The number ONE thunderstorm-related killer -- averages 146 deaths annually. Lightning Kills 75 to 100 people each year Damaging Straight-Line Winds Can reach speeds of 140 mph Large Hail Often the size of golf balls and occasionally can reach grapefruit size. Hail causes several hundred million dollars in damage annually to property and crops.

29 Tornado Watch Tornado Watch alert people to the possibility of tornadoes in a specified area for a particular time.

30 Tornado Warning Tornado Warning A tornado warning is issued when a tornado has actually been sighted in an area or is indicated by weather radar. With new technology we have gone from 5 minutes to 15 minutes of warning time for tornadoes

31 Radar Tornadoes (J-Hook)

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33 Tornado Safety If you are caught outdoors, seek shelter in a basement, shelter or sturdy building. If you cannot quickly get to a shelter, immediately get into a vehicle, buckle your seat belt and try to drive to the closest sturdy shelter. If flying debris occurs while you are driving, pull over and park. You have the following options as a last resort:

34 Tornado Safety Stay in the car with the seat belt on. Put your head down below the windows, covering with your hands or a blanket if possible. If you can safely get noticeably lower than the level of the roadway, exit your car, and lie in that area, covering your head with your hands.

35 Tornado Safety Flying and falling debris is the biggest hazard in a tornado. To be safe, you should get inside, get down and cover up. Underground or in a Safe Room is your first choice. If no underground shelter is available, get to the center of a sturdy building on the lowest level. Put as many walls between you and the tornado as possible. Stay away from windows and doors. Cover up to help minimize being injured by flying or falling debris.