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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 - PowerPoint PPT PresentationTRANSCRIPT
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
More about Weather:
Storm Systems:
Storm Systems:
High and Low Pressure 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
Tornado Formation
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
Songer http://www.pitt.edu/~super1/lecture/lec0761/005.htm
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 Occurrence by Category
Tornado Deaths by Category
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
Satellite image taken May 3, 1999 @ 645 CDT
View from the air of a tornado path in
Central OK
Tornado near Amber, OK at 6:30 CDT
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)
• Tornado warning: 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!!
Early Warning Systems