Extreme Weather

ByHeath Abell

My Experience

• Ever since I was a child, I have been fascinated by the weather. I’ve always wondered how rain, snow, and other precipitation was formed. When I was about 6 years old, I saw my first tornado. That sparked an interest in me for destructive weather. In this inquiry I am going to explore some extreme weather, focusing on tornadoes and hurricanes.

Questions

• What is a tornado?• How are tornadoes formed?• How big can a tornado become?• What is the largest tornado ever recorded?• Where is the most likely place for a tornado to

occur in the U.S.?

Questions

• What is a hurricane?• How is a hurricane formed?• How strong can a hurricane become?• What is the strongest hurricane recorded?• Where is a hurricane most likely to strike in

the U.S.?

Standards

• 4.3.4 Describe some of the effects of oceans on climate.

• 4.3.5 Describe how waves, wind, water, and glacial ice shape and reshape the Earth's land surface by erosion of rock and soil in some areas and depositing them in other areas.

• 5.3.5 Observe and explain that clouds and fog are made of tiny droplets of water.

What is a Tornado?

• A tornado is a powerful column of winds spiraling around a center of low atmospheric pressure.

• It looks like a large black funnel hanging down from a storm cloud.

How are Tornadoes formed?

• Tornadoes usually are produced by thunderstorms.

• Thunderstorms act as earth’s cooling agent. When temperatures vary greatly between the ground and the atmosphere air rises rapidly and condenses to form thunderheads.

How are Tornadoes formed? (cont’d)

• This heated updraft collides with higher cold air and creates turbulent winds surrounding it. These winds are forced into a violent upward spin and are the beginnings of a tornado. Then, if the momentum of the vortex generates sufficient strength it will extend a funnel below the cloud base to the ground.

How big can a tornado become?• Tornado strength is classified on a scale determined by T.

Theodore Fujita in 1971.• F0 – Gale

– With winds of less than 73 miles per hour (116 kph), F0 tornadoes are called "gale tornadoes" and cause some damage to chimneys, damage sign boards, and break branches off of trees and topple shallow-rooted trees.

• F1 – Moderate– With winds from 73 to 112 mph (117-180 kph), F1 tornadoes

are called "moderate tornadoes." They peel surfaces off of roofs, push mobile homes off of their foundations or even overturn them, and push cars off of the road. F0 and F1 tornadoes are considered weak; 74% of all measured tornadoes from 1950 to 1994 are weak.

How big can a tornado become? (cont’d)

• F2 – Significant– With winds from 113-157 mph (181-253 kph), F2 tornadoes

are called "significant tornadoes" and cause considerable damage. They can tear the roofs off of light frame houses, demolish mobile homes, overturn railroad boxcars, uproot or snap large trees, lift cars off the ground, and turn light objects into missiles.

• F3 – Severe– With winds from 158-206 mph (254-332 kph), F3 tornadoes

are called "severe tornadoes." They can tear the roofs and walls off of well-constructed houses, uproot the trees in a forest, overturn entire trains, and can throw cars. F2 and F3 tornadoes are considered strong and account for 25% of all tornadoes measured from 1950 to 1994.

How big can a tornado become? (cont’d)

• F4 – Devastating– With winds from 207-260 mph (333-416 kph), F4 tornadoes are called

"devastating tornadoes." They level well-constructed houses, blow structures with weak foundations some distances, and turn large objects into missiles.

• F5 – Incredible– With winds from 261-318 mph (417-509 kph), F5 tornadoes are called

"incredible tornadoes." They lift and blow strong houses, debark trees, cause car-sized objects to fly through the air, and cause incredible damage and phenomena to occur. F4 and F5 tornadoes are called violent and account for a mere 1% of all tornadoes measured from 1950 to 1994. Very few F5 tornadoes occur.

• F6 – Inconceivable– With winds above 318 mph (509 kph), F6 tornadoes are considered

"inconceivable tornadoes." No F6 has ever been recorded and the wind speeds are very unlikely. It would be difficult to measure such a tornado as there would be no objects left to study. Some continue to measure tornadoes up to F12 and Mach 1 (the speed of sound) at 761.5 mph (1218.4 kph) but again, this a hypothetical modification of the Fujita Scale.

What is the largest tornado ever recorded?

• The Great Tri-State Tornado of Wednesday, March 18, 1925, crossed from south eastern Missouri, through southern Illinois, then into southwestern Indiana, and was the deadliest tornado in U.S. history. With 695 confirmed fatalities. The continuous 219 mile track left by the tornado was the longest ever recorded in the world. Historians would recognize it as an example of the maximum issued rating of an F5 on the Fujita scale.

Where is a tornado most likely to occur in the U.S.?

What is a hurricane?

• A hurricane is an intense, rotating oceanic weather system that possesses maximum sustained winds exceeding 119 km/hr (74 mph). It forms and intensifies over tropical oceanic regions

How is a hurricane formed?• Hurricanes begin as tropical storms over the warm moist waters of

the Atlantic and Pacific Oceans near the equator.• The winds begin to circle counterclockwise north of the equator or

clockwise south of the equator.• The relatively peaceful center of the hurricane is called the eye.• Around this center winds move at speeds between 74 and 200

miles per hour.• As long as the hurricane remains over waters of 79F or warmer, it

continues to pull moisture from the surface and grow in size and force.

• When a hurricane crosses land or cooler waters, it loses its source of power, and its wind gradually slow until they are no longer of hurricane force--less than 74 miles per hour.

How strong came a hurricane become?

• The Saffir-Simpson Hurricane Scale rates hurricanes from category 1 through category 5 in order of increasing intensity. Each intensity category specifies the range of conditions based on four criteria: barometric (central) pressure, wind speed, storm surge, and damage potential.

What is the strongest hurricane recorded?

• Hurricane Wilma– The most intense storm on record for the Atlantic

Basin, minimum central pressure for Wilma, on October 19th reached 882 mb. Peak sustained winds reached 175 mph as the storm tracked west through the Caribbean Sea.

– At least 63 deaths were reported, and damage is estimated at over $29.1 billion.

Where is a hurricane most likely to strike in the U.S.?

• Hurricanes are most likely to strike the U.S. along its eastern boarder or along the gulf coast.

Resources• http://library.thinkquest.org/C003603/english/

tornadoes/whatisatornado.shtml• http://media.tbo.com/photos/trib/2007/feb/

0202tornadographic.jpg• http://wiki.answers.com/Q/

What_was_the_largest_tornado_ever_recorded_in_the_US_in_terms_of_width_of_path

• http://www.cotf.edu/ete/modules/sevweath/swhoware.html

• http://library.thinkquest.org/03oct/01424/how_is_a_hurricane_measured.htm