Daulatpur-Saturia (03:04)

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The deadliest tornado occurred in Bangladesh in April, 1989; it cut a 50 mile path of destruction, leaving 80,000 homeless, injuring 12,000, and killing 1,300. It originated when warm, humid air rose and met cool dry air; supercell thunderstorms formed and a funnel emerged from its base.

Terrible Tuesday and Classifications (03:44)

Tornado types include single funnel, wedge, multiple vortex, and satellite; dust devils, water spouts, and fire whirls are sub-tornadoes. In April 1979, 30 twisters struck Wichita Falls, killing 56 and injuring 1,700.

Oklahoma Outbreak (06:12)

Eighty percent of twisters occur in North America; ideal conditions are created in Tornado Alley by Rocky Mountain cold systems meeting warm air from the Gulf of Mexico. During May 1999, three days of violent storms ripped through four states; the cleanup cost neared two billion dollars.

Measuring Intensity (05:15)

Tornado strength is measured by the Fujita scale, using damage to estimate power. Rare and destructive F-V twisters have reached 318 miles per hour. Debby LeFrance is a direct hit survivor, tossed from her Texas home in May 1997. The event cost 190 million in damages, and killed 27 people.

Tri-State Twister (02:58)

In March 1925, a massive tornado raged through Missouri, Illinois, and Indiana, killing 695 and injuring 2000; it caused more damage in one city than any other in history. It reached over 200 miles per hour, and demolished everything in its 219 mile long path.

Prediction (05:29)

National Oceanic and Atmospheric Administration's weather service issues tornado warnings; forecasters study maps, analyze data, and create models to simulate potential outcomes. They release a Severe Weather Watch when threatening conditions become apparent. Spotter Networks respond when twisters are anticipated; they track storms visually, sometimes sustaining injuries.

Red River Valley Outbreak (02:39)

Tornadoes have formed suddenly when conditions are ideal; in April 1979, Wichita Falls bank employees secured themselves in the money vault to avoid impact. The Terrible Tuesday twister killed 42 people and caused 400 million in damages.

Super Outbreak (01:55)

On April 3rd, 1974, the largest tornado swarm on record impacted 13 states. Three hundred people were killed and 5,000 injured when 148 twisters touched down from Mississippi to Ontario, creating a 2,500 mile long path of destruction.

Accompanying Dangers (05:03)

In March 2000, Texas supercell tornadoes came with flash floods; hailstones inflicted property damage, and one fatality. Debris hurled by high wind speeds, causes most deaths and injuries during the storms. On December 8th, 1954, Gunnersbury was struck by a twister generating 200 mile per hour winds; the Kensal Rise Tornado hit London in 2006.

Impact and Energy Research (03:13)

Tornadoes cause massive damage; wind engineers at Texas Tech University experiment with a cannon to duplicate storm effects. Twisters can transport objects, raining them down miles away. Louis Michaud endeavors to generate small twisters and harness their power.

Storm Chasers (03:49)

Tour companies use mobile alert systems and speedy vehicles to offer vacations in Tornado Alley. Skilled spotters and meteorologists lead the adventures. New technologies give measurement and prediction, but do not offer prevention or containment.

Credits: Twisters And Weird Weather (00:28)

Credits: Twisters And Weird Weather