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Science 10. Mr. Jean May 17 th , 2012. The plan:. Video clips of the day Storm Systems & Diagrams Tornadoes Storm Chasers. What’s coming up?. Chapter #13 Assignment/Quiz Heat Capacities How does it work Calculations for heating water Calculations for state/phase chance
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Science 10 Mr. Jean May 17th, 2012
The plan: • Video clips of the day • Storm Systems & Diagrams • Tornadoes • Storm Chasers
What’s coming up? • Chapter #13 • Assignment/Quiz • Heat Capacities • How does it work • Calculations for heating water • Calculations for state/phase chance • Types of clouds • Weather systems
Tornado History • The “Tri-State Tornado” is the most violent tornado on record • On March 18, 1925, the tornado formed in Missouri and traveled 219 miles across Illinois into Indiana • The funnel was up to .75 miles across and traveled as fast as 73 mph. • It killed approximately 635 people
Tornado A violently rotating column of air (vortex), hanging from a cumulonimbus cloud, with circulation that touches the surface of the earth
Supercell Storm • Severe weather occurs as strong downbursts…large hail…occasional flash floods and weak to violent tornadoes • Severe event almost always occur near the updraft interface typically in the rear (southwest) storm flank. Some of the supercells have the interface on the front of the southeast flank • High predictability of occurrence of severe events once a storm is identified as a supercell • Extremely dangerous to public • Extremely dangerous to aviation
The Supercell Tornado forms here
Tornado Facts • Tornados can occur almost anywhere in the world • Duration: a few minutes • Diameter (Avg.): 0.4 km • Length of path (Avg.): 6 km • Funnel can travel from 0 mph up to ~70 mph, usually travels at 30 mph • 99% of all tornados in Northern Hemisphere rotate counterclockwise • Texas is #1 for frequency of tornados per year • Between 1950 and 1995 Texas had 5,722 recorded tornados • Risk of death in a tornado in Texas: 1 in 1,054,267 • Texas cost per person per year for tornados: $3.94
Tornado Myths • A highway overpass is a safe place to take shelter under during a tornado • Opening windows during a tornado will help balance the pressure between the inside and outside of the house and may prevent destruction of the structure • One should seek shelter in the southwest corner of a house or basement.
Tornado Oddities • Tornados are reported to routinely carry objects many miles and have: • sucked the frogs out of a pond and dropped them on a town • carried a necktie rack with 10 ties attached 40 miles • carried a flour sack 110 miles from a mill • Tornados also drive objects into other objects and have: • Driven splinters into an iron fire hydrant • Driven straw and grass into telephone poles
When Tornados Occur • Anytime of the year- usually in the spring, summer, and fall • Most tornados occur during late spring in the month of May • Between the late afternoon and early evening is when most tornados are spawned • The most dangerous time for formation during evening hours A typical late afternoon tornado
Where Tornados Occur Tornado Alley covers the Great Plains states
Tornado Wind Speed In 1971, Dr. Fujita developed a way of measuring the winds of a tornado. He reasoned that there was a link between wind speed and the damage caused by a tornado. There are 6 categories of tornados (F0 – F5)
F0 Category • (Weak) winds (40-72) mph , little damage • Damage: tree branches snapped, chimneys toppled, signs torn down
F3 Category • (Strong) winds: (158-206) mph, severe damage • Damage: most trees uprooted, trains overturned, roofs torn off, walls demolished
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
Tornado Forecasting Meteorologists who predict tornado development analyze the current atmospheric conditions such as: air temp., barometric pressure, the locations of fronts, wind velocities, convection, etc. Probably the most useful tool a meteorologist can use to identify tornados is radar, specifically Doppler radar (WSR-88D)
Tornados on Radar Doppler image of a rain-wrapped tornado
The Life cycle of a Tornado • The “Life Cycle” of a tornado consists of four distinct stages. • These stages were first determined during the Union City, OK tornado of 1973 • Most tornadic events are difficult to classify and may not exhibit stages that are obvious to the observer • Sometimes events become unclear: one tornado weakens another appears, or single event? • Tornados do not “skip” – gaps in damage path may indicate a temporary weakening in intensity
Beginning Stage: Tornado begins as a rotating wall cloud which quickly evolves into a funnel
Early Stage: Tornado funnel develops (may be transparent) and extends down from the cloud to the ground
Mature Stage: Tornado funnel reaches maximum width as well as maximum intensity then begins to shrink
Decay Stage: tornado may remain stationary and take on a ropelike appearance before dissipating
The Tornado Outbreak of May 3, 1999 • Severe thunderstorms move into Ok, TX, Ks and spawn estimated 70 tornados, most occurred in Oklahoma • In Oklahoma 40 people killed, 675 injured • Damage: $1.2 billion • Largest tornado outbreak in Oklahoma history • 1,780 homes completely destroyed • 6,550 homes damaged
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
Waterspouts A waterspout is a tornado that forms over a body of water, or a tornado that moves from land onto water
Storm Chasers Storm chasers are a group made up of meteorologists and scientists, as well as amateur observers who voluntarily put themselves in the path of a severe thunderstorm in order to hopefully observe a tornado and obtain photographs and scientific data.
Tornado Indicators • A greenish colored sky associated with the thunderstorm (caused possibly by the scattering of light by particles in the sky) • Mammatus clouds • 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!
Mammatus clouds Green sky
Tornado Damage Tornados 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
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) • Tornadowarning: 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!!
