Tornados Author R.T. Schindler Distributed by the Disaster Team Supercourse (

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

First Tornado Forecast On March, , Major Fawbush and Captain Miller determined that the conditions of the atmosphere just west of Tinker AFB, OK were suitable for tornado development. The first tornado forecast ever was issued. A few hours later, a tornado arrived causing significant damage to the base. However, no deaths and only a few injuries occurred because many had been warned by the tornado forecast.

Tornado Tornado comes from the Spanish word, tronada, which means “thunderstorm.” 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 Supercells are storms --- usually, but not necessarily, thunderstorms --- that contain updrafts that rotate about a vertical axis. This rotation is derived from shear in the environmental wind field (that is, a change in wind direction and / or speed with height) surrounding the storm as it begins to grow. Supercells often produce damaging wind, large hail, and tornadoes, and most strong to violent tornadoes are associated with supercells.

The Supercell Tornado forms here

Tornado Formation

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

Where Tornados Occur Tornado Alley covers the Great Plains states

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

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

F1 Category (Moderate) winds (86-110) mph, moderate damage Damage: peels surfaces of roofs, mobile homes pushed overt, and moving autos pushed off roads

F2 Category (Significant)winds ( ) mph, Significant damage Damage: roofs torn off frame houses; mobile homes demolished; large trees snapped or uprooted; light-object missiles generate

F3 Category (Strong) winds: ( ) mph, severe damage Damage: most trees uprooted, trains overturned, roofs torn off, walls demolished

F4 Category (Devestating) winds: ( ) mph, Devastating damage Damage: Well-constructed houses leveled, structures blown off weak foundations, large objects thrown

F5 Category (Violent) winds: ( ) 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 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

View from the air of a tornado path in Central OK

Tornado near Amber, OK at 6:30 CDT

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

Additional Lectures by world experts "Tornadoes" lecture by Lillibridge, Scott R "A Historical Look at Tornadoes: Damage and Death" by Harold Brooks which have also three more links to online lectures: Development of synthetic severe thunderstorm climatologies ( Tornado deaths in the US and mobile homes ( The distribution of tornadoes by F-scale in time and space Harold 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

Bibliography http// 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