tornadoes - n ECT ceanography Natural Disasters Torn ado es...

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Unformatted text preview: n ECT ceanography Natural Disasters Torn ado es shapes known as signa- tures of potential toma- Tomadoes combine does: powerful winds speeds, 0 Bright V-sliiaped cloud wedge _ . wit overs ooting towers o 390 to 330 miles an hour, convection Wlth small lifetimes, 10 0 Mammatus cloud shape, a pecu- rninutes to a maximum of two hours in a very nar- row, sharply defined path. In shape, they resemble ei- ther a long thin rope or a fat inverted bell. Toma- does typically form along the cold front of a fast moving, mid-latitude cy- clonic storm system. When a tornado does appear, it usually appears from the storm’s rear side where the stream of cool air from a vertical downdraft circu- lates into the warm, moist lower-level horizontal in- flow. The intensity of a tornado’s rotation, its complexity (vortex) and its severe effect on atmo- spheric pressure account for both the destructive- ness of tornadoes and their unpredictability. The most promising technol- ogy for tornado detection is Doppler radar. Doppler radar is able to indicate the direction of rotation liar pendulous formation that hangs udder like (the name is derived from the Latin word for having breasts.) below the anvil shaped tops of thunderstorms. Rotary circulation in wind- tattered cloud bases. The National Weather Service (NWS) National Se- vere Storms Forecast Cen- ter in Kansas City, MO, provides information on severe thunderstorms and tornadoes to the gen- eral public, news media, emergency managers and and the speed that the tor— nado is moving. Satellites are useful in spotting tornadoes, pro- viding images of cloud law enforcement person- nel. The center uses Doppler radar, wind pro- filers and the networks of automated surface ob- © 1998 Project Oceanography Spring Series 9 serving systems (ASOS) across the United States to assist in the prediction and identification process for severe thunderstorm and tornado watches and warnings. A tornado watch is is- sued for a specific location when thunderstorms capa- ble of producing tornadoes are recognized and arrival is expected in a few hours. A tornado warning is is- sued when tornadoes are spotted or Doppler radar identifies a distinctive “hook-shaped” area within a local partition of a thun- derstorm line that is likely to form a tornado. When a tornado watch or warning is issued, local authorities are placed on alert to assist in identify- ing and locating possible tornadoes. When a tor- nado is detected, emer- gency operations person- nel and law enforcement agencies are alerted imme- diately. Warnings are broadcast to the public through radio, television V and alarm systems. Emer- gency managers and local law enforcement officials sound sirens to notify those who have not al- ready received the infor- mation by television, radio Natural DisasterszTomadoes. Lightning and Tsunamis : JECT ceanography Natural Disasters: Wind Speed and Damage Tornadoes can range in _ wind speed from 40 to 350 miles per hour, but ones over 300 miles per hour are rare. When a tornado approaches a house, the atmospheric pressure within the house is greater than the pressure within the tornado. Air can not escape rapidly enough. This causes the windows to explode (break outward) and the walls may explode, causing the roof to col- lapse. In other instances, the tornado may lift the roof off the house but leave the walls intact. Tornado Structure Formation When a moving mass of cold air overtakes and traps an underlying layer of warm moist air, the warm air is drawn up into the core of the storm in a spiraling upward motion. At the same time, the cold air spirals downward, cre- ating a vortex, or twisting funnel cloud. The destruc- tive capabilities of torna- does come partially from their extremely high wind velocities, and partially from the near-vacuum that exists within the vortex. The air ,pressure inside the vortex may be as low as 60 percent of normal atmo- spheric pressure; buildings can explode and disinte- grate as a result of the pressure differential be- tween the inside and the outside air. The partial vacuum also causes the tornado to suck up soil and debris, which gives the funnel cloud its typical dark, ominous appearance. Where Tornadoes Form Tornadoes occur world- wide; however, they are most common in the United States. About 80% of the US tornadoes ravage three states: Texas, Okla- homa and Kansas. Warm moist air flowing up from the Gulf of Mexico collides with cool dry air from Canada, channeled east by the Rockies. This causes most of the tornadoes in the central part of the country. © 1998 Pro_rect Oceanography Spring Series 10 What to do if a Tornado Hits If there is a potential that a tornado may form in your area, the National Weather Service will issue a Tornado Watch. If a Tornado Warning is issued, it means that a tornado or in- cipient tornado has been sighted. Here are a few tips on what to do if a tornado hits , your area: 0 If you are not indoors. take cover! Use a battery-powered radio to find out what is happening in your area. 0 Go to an inside wall on the lowest floor. kneel on the floor facing the wall and put your hands over your head. Ideally. a room with no win- dows (often a bathroom. the base- ment or under a staircase) would be the safest place. 0 If in a classroom. stay away from rooms with mde roots that could col- lapse easily. such as auditoriums or gymnasiums. 0 If you are stuck outside and see a tornado approaching, go to a safe place such as a ditch or underneath a steel bridge. You can crawl up close to the support beams and stand a good chance of riding out the storm. If you are in a car. get out: a tornado can outrun even a very fast car. Natural Disasters:Tomadocs. Lighuiing and Tsunamis The Fu 'ita-Pearson Tornado Intensity Scale Professor Fujita and Dr. Allen Pearson, Director of NSSFC (National Severe Storm Forecast Center) brought the scale into widespread use in the early 1970’s. The Fujita Scale is based on damage, not the appearance of the funnel. The funnel size does not necessarily indicate speed or intensity. This scale measures both the path length and width awn-wt. Mn.— 400 Inph Someroo damage, re 5 ran es 0 tr, shallow rooted trees. Moderate 73- 112 mph Removes shingles from roofs; mobile homes moved from T oma d O foundation or overturned ; moving automobiles are pushed off the roads: attached garages may be destroyed. Significant 1 13-157 Inpr Considerable damage. Roofs torn off frame houses; mobile F- 2 tornado homes demolished; large trees snapped/uprooted; small flying debris becomes hazardous. Severe 1 58—206 mph Roof and walls torn from houses; trains overturned, most F- 3 "[0me trees in tornado's path are uprooted Devastating 207-260 Inph Houses are leveled, cars are thrown. large debris becomes Tornado dangerous Incredible 261-3 1 8 Inph Strong frame house lifted off foundations and carried F- S Tornado considerable distances to disintegrate; automobiles and other debris fly at high rates of speed F 6 Inconceivable 319-379 mph These Winds are higlflymflikely- ' Tornado © 1998 Project Oceanography Spring Series 11 Natural Disasters:Tomadoes, Lightning and Tsunamis E O figgnogmphy , Natural Disasters Wind SpeedNeeded to Lift an Object Quite—ct 3 /4" sheet of plywood 95 31 light mobile home 8‘ x 40' 4800 S4 brick 3 S6 heavy mobile home 39,200 88 concrete block 40 99 compact car 2000 105 standard car 4000 1 14 fertilizer tank 26.000 202 brick chimney Date Name or # of Deaths Number of Estimated Damage Location Tornadoes States Affected gin millions) 3/18/1925 Tri-state 7 740 6 $18 4/ 5-6/ 1936 Tupelo— Gainesville 1 7 446 L" 518 2/19/1884 Enigma 60 420 8 S3 3/21-22/1932 North Alabama 33 334 7 SS 4/3-4/1974 Super 148 31 S 13 N/A 4/24-25/1908 Louisiana- Georgia 18 3 10 UI (I) p—a 5/27/1896 St. Louis. MO 18 306 3 $15 4/11/12/1965 Palm Sunday 51 256 6 $200 © 1998 Project Oceanography Spring Series 12 Natural DisasterstTomadoes. Lightning and Tsunamis K OIECT ceanogmphy Natural Disasters}? Activities The best method of tracking a tornado is Doppler radar. Government agencies and university re- TOrnado Bottles searchers use this method W1 1 . to track weather data. They ' laige' C ear p asnc home use vehicles such as trucks wnh cap and vans equipped mm the water h . Doppler radar on the roof of : S avmgs the vehicle. They will chase a storm in order to gain in- formation on the weather patterns. This is not safe and should not be at- tempted without expert Chasers. Water spouts are toma- does that form over water. They pick up the water and carry it in its cyclone. Water spouts are capable of si- phoning millions of tons of water from water bodies. They are dangerous to boaters. When they make landfall, they can also cause severe coastal damage. 0 metal or plastic confetti 0 bits of Easter grass Fill the bottle with water. Add crayon shavings, glitter or other small floating mate- rials such as Easter grass or plastic confetti. Replace the cap and tighten. Shake the bottle and watch the objects move. Try to make a tor- nado movement by swirling in one direction. Experi- ment with designs and pat- terns in movement by tip- ping and shaking the bottle different ways. For a different look: materials - Z-empty two liter bottles o water 0 tornado cap (purchased at most educational sup- ply stores) © 1998 Project Oceanography Spring Series 13 Fill one bottle half-qu and place the cap on that bottle. Attach the other bottle to the opposite end of the cap. Turn bottle over see the swirling pattern of the wa- ter, similar to a tornado. Words to know: Vortex Cyclone Fajita-Pearson Scale _ Tornado Watch Tornado Warning Doppler Radar Discussion Questions: 1. A tornado with what wind speeds can over turn a train? 2. What should you do if you are at school and a tornado warning is issued? Naturai Disasters:Tomadocs. Lightning and Tsunamis ...
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