Tornados

R.T. Schindler

Spring storm and tornadoes in Kansas

Additional Lectures by world experts

"Tornadoes" lecture by Lillibridge, Scott R"A Historical Look at Tornadoes: Damage and Death” by Harold Brookswhich have also three more links to online lectures: 1.Development of synthetic severe thunderstorm climatologies2.Tornado deaths in the US and mobile homes3.The distribution of tornadoes by F-scale in time and spaceHarold Brooks “Tornado-Related deaths and injuries due to the May 3, 1999 by Sheryll Brown, Pam Archer,Elizabeth Kruger and corresponding author Sue Mallonee from Injury Prevention Service, Oklahoma State Department of Health

Tornado History

First Tornado Forecast

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

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

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

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

Bibliography• http//www.photolib.noaa.gov/• http://www.nsl.noaa.gov/GoldenAnniversary• http://www.srh.noaa.gov/oun/• http://www.usatoday.com/weather• www.nsl.noaa.gov/~doswell?a_tornado/atornado.html• http://www.disastercenter.com/• http://www.tornadoproject.com/• Church C., Burgess D., Doswell C., Davies-Jones,R., ed.

The Tornado: Its Structure, Dynamics, Prediction, and Hazards.

• American Geophysical Union Press: 2000• Liu, Henry. Calculation Of Wind Speeds Required to

Damage or Destroy Buildings. Publication within The Tornado