Unformatted text preview: Tornadoes Tornadoes
Winds Tornadoes by Year, 19502004 Tornadoes by Year, 19502004 Original Fujita Scale circa 1971
FujitaScale Mean Wind Speed Range* (mph) 40 to 72 (45 – 78) 73 to 112 (80–118) 113 to 157 (119–161) 158 to 206 (162-209) 207 to 260 (210-261) 261 to 318 (262-317) 319 to sonic speed Qualitative damage description F0 F1 Light damage – some damage to chimneys and TV antennae; breaks twigs off trees; pushes over shallow rooted trees. Moderate damage – peels surface off roots; windows broken; light trailer houses pushed or overturned; some trees uprooted or snapped; moving automobiles pushed off the road. 73 mph is the beginning of hurricane wind speed. Considerable damage – roofs torn off frame houses leaving strong upright walls; weak buildings in rural areas demolished; trailer houses destroyed; large trees snapped or uprooted; railroad boxcars pushed over; light object missiles generated; cars blown off highway. Severe damage – roofs and some walls torn off frame houses; some rural buildings completely demolished; trains overturned; steel-framed hangar-warehouse type structures torn; cars lifted off the ground; most trees in a forest uprooted, snapped or leveled. Devastating damage – whole frame houses leveled, leaving piles of debris; steel structures badly damaged; trees debarked by small flying debris; cars and trains thrown some distances or rolled considerable distances; large missiles generated. Incredible damage – whole frame houses tossed off foundations; steel-reinforced concrete structures badly damaged; automobile-sized missiles generated; incredible phenomena can occur. Inconceivable damage – should a tornado with the maximum wind speed in excess of F6 occur, the extent and types of damage may not be conceived. A number of missiles such as ice boxes, water heaters, storage tanks, automobiles etc will create serious secondary damage on structures. F2 F3 F4 F5 F6-F12 Tornado Risk Tornado Risk
► “Tornado alley” from Texas to Michigan ► Smaller “tornado alleys” – e.g., NW Alabama, north metro of Atlanta ► Big cities and the “heat island effect” – but … ► Tornado watches and warnings – Doppler radar picks up wind speed and direction. New radar picks up details within supercells, e.g., amount of rain and hail. ► Weather radio – Specific Area Message Encoding (SAME) – warning by county ► Alert and warning systems – sirens, lights, radio Super Outbreak of 1974 Super Outbreak of 1974
April 34, 1974 148 tornadoes 30 tornadoes of F4 or higher 119 tornadoes with paths of one mile or more 315 people killed and 6,142 injured 54 people killed and 1150 injured, 300 homes destroyed and 2,100 damaged in Xenia, Ohio Palm Sunday Tornado in 1994 Palm Sunday Tornado in 1994
► 22 killed in a church in Goshen, Alabama ► Lack of warning – although police officer saw storm coming and threat announced by NWS ► Lack of weather radio ► Lack of appropriate protective action ► Weaknesses in weather warning system [Case study in Living with Hazards, Dealing with Disasters] Protective Action Protective Action
► Go to basement ► Go to interior room without windows ► Go to bathroom on first floor ► Outside: get out of car and lie in ditch covering head ► Build “safe room” What is the Safest Place What is the Safest Place in the General Classroom Building?
What is the safest place in your home? Fun Site
► Storm Spotting • Storm Chasing • Severe ► National Association of Storm Chasers and Weather Safety and Education • Emergency Operations and Communications ► http://www.chasingstorms.com/ ...
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- Spring '07
- Wind speed, Fujita scale, frame houses, Tornado Risk Tornado