Tornadoes & hurricanes


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Tornadoes & hurricanes

  1. 1. Tornadoes & Hurricanes <br />By: Amber Ethridge<br />6th Grade Science<br />Teacher Mrs. France Burkes<br />
  2. 2. Tornadoes<br />
  3. 3. What is a tornado<br />Atornado is a violent rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of up to 300 mph. They can destroy large buildings, uproot trees and throw vehicles hundreds of yards. They can also drive straw into trees. Damage paths can be in excess of one mile wide to 50 miles long. In an average year, 1000 tornadoes are reported nationwide. <br />
  4. 4. How they are formed<br />Most tornadoes form from thunderstorms. Youneed warm, moist air from the Gulf of Mexico and cool, dry air from Canada. When these two air masses meet, they create instability in the atmosphere. Achange in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere. Rising air within the updraft tilts the rotating air from horizontal to vertical. An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.<br />
  5. 5. How Long Does a Tornado Last?Tornadoes usually last just a few minutes. The shortest last for only a few seconds, but the longest (and most dangerous) can last for over an hour (but these are extremely rare)! <br />Wind Speed of a TornadoThe average wind speeds in most tornadoes are about 112 mph (180 km/h) or less. Winds in the most extreme tornadoes can be over 300 mph (500 km/h). <br />Tornadoes are ranked using a scale called the Fujita Scale, five categories of wind speed that are estimated the damage left behind (these are not wind speed measurements, since most wind-speed measuring devices are destroyed during tornadoes, and since the tornadoes die out so quickly, Doppler radar wind measurements are not usually done). <br />F-5 tornadoes are the most dangerous type (and the rarest type). <br />F-0 40-72 mph, Light damage, chimney damage, tree branches broken <br />F-1 73-112 mph, Moderate damage, mobile homes pushed off foundation or flipped over <br />F-2 113-157 mph, Considerable damage, mobile homes demolished, trees uprooted <br />F-3 158-205 mph, Severe damage, roofs and walls torn down, trains overturned, cars thrown around <br />F-4 207-260 mph, Devastating damage, well-constructed walls leveled <br />F-5 261-318 mph, Violent damage, homes lifted off foundation and carried considerable distances, autos thrown as far as 100 meters. <br />
  6. 6. Tornado Watch and WarningMeteorologists (scientists who study the weather) can sometimes warn people when conditions are right for tornadoes in a particular area, but the ability to predict tornadoes is very limited. People usually only have a few minutes warning (if that much). When you hear a tornado warning, find shelter IMMEDIATELY! <br />The following are tornado warning terms: Tornado Watch-- This means that tornadoes may form in the area, because conditions are favorable for their formation. People should stay tuned to radio or TV weather and listen for local warning sirens (but these are only available in some areas). Tornado Warning-- A tornado has formed in the area! Find shelter immediately! A basement is best, but if that isn't available, go to an interior room or closet in a house, and stay far away from windows. If there aren't any buildings around, lie face-down on the ground in a low lying area (like a ditch) and cover your head with your hands for protection. <br />
  7. 7. Facts<br />The oldest Known Tornado - Date: 1884 August 28 Historic NWS Collection 22 miles southwest of Howard, South Dakota Courtesy NOAA/Department of Commerce<br />The most powerful Tornadoes occur in the United States. <br />A typicaltornado only lasts for a few minutes. <br />Every tornadohas its own color, sound and shape. <br />You need to step on the pedal of a car pass 70 miles per hour to outrun the fastest tornadoes. <br />The chances that a tornado is a F5, the highest classification for a tornado on the F-scale, is less than 0.1% <br />Tornadoes have been reported in every state in the US and also in every season. <br />A Tornado can occur at any time, but most often between 3pm and 9pm.<br />
  8. 8. Hurricanes<br />
  9. 9. What is a Hurricanes<br />A hurricane is a huge storm! It can be up to 600 miles across and have strong winds spiraling inward and upward at speeds of 75 to 200 mph. Each hurricane usually lasts for over a week, moving 10-20 miles per hour over the open ocean. Hurricanes gather heat and energy through contact with warm ocean waters. Evaporation from the seawater increases their power. Hurricanes rotate in a counter-clockwise direction around an "eye." The center of the storm or "eye" is the calmest part. It has only light winds and fair weather. When they come onto land, the heavy rain, strong winds and large waves can damage buildings, trees and cars.<br />
  10. 10. HURRICANE WATCHAn announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds. <br />HURRICANE WARNINGAn announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds. <br />
  11. 11. How they are formed<br />Hurricanes only form over really warm ocean water of 80°F or warmer. The atmosphere (the air) must cool off very quickly the higher you go. Also, the wind must be blowing in the same direction and at the same speed to force air upward from the ocean surface. Winds flow outward above the storm allowing the air below to rise. Hurricanes typically form between 5 to 15 degrees latitude north and south of the equator. The Coriolis Force is needed to create the spin in the hurricane and it becomes too weak near the equator, so hurricanes can never form there. <br />
  12. 12. How long do they last?<br />There’s no substantial answer to gauge how long does a hurricane survive. But according to some researches, it has been studied that, usually, hurricanes survive for around two to four weeks. It is very uncommon for a hurricane to survive for a longer duration, because ultimately it strikes land or cold water, where it cannot continue to exist. Only one hurricane that lasted for more than a day was Hurricane Erin in the Arctic, 2001.<br />Wind speed of a hurricane<br />"Level 1, 74-95 mphLevel 2, 96-110 mphLevel 3, 111-130 mphLevel 4, 131-155 mphLevel 5, 156 mph”<br />
  13. 13. Facts<br />The first time anyone flew into a hurricane happened in 1943 in the middle of World War II<br />The word hurricane comes from the Taino Native American word, hurucane, meaning evil spirit of the wind.<br />A tropical storm is classified as a hurricane once winds goes up to 74 miles per hour or higher.<br />Hurricanes are the only weather disasters that have been given their own names.<br />All hurricanes begin life in a warm moist atmosphere over tropical ocean waters.<br />A typical hurricane can dump 6 inches to a foot of rain across a region.<br />The most violent winds and heaviest rains take place in the eye wall, the ring of clouds and thunderstorms closely surrounding the eye.<br />Every second, a large hurricane releases the energy of 10 atomic bombs.<br />
  14. 14. Thank you very much<br />Hope you liked it<br />