Severe Weather and Storms ◦ Storms: ◦ Violent disturbances within the atmosphere. ◦ Caused by sudden changes in air pressure which cause rapid air movement in an area. ◦ Similar conditions often produce different types of storms. Thunderstorms ◦ A thunderstorm is a small storm often accompanied by heavy precipitation and frequent thunder and lightning. ◦ Form in large cumulonimbus clouds (also called thunderheads) on hot, humid afternoons Thunderstorms ◦ Warm, humid air rises rapidly and the air cools, forming dense thunderhead clouds ◦ Heavy rain falls, sometimes along with hail ◦ Within the thunderhead cloud there are strong updrafts and downdrafts Lightning ◦ Lightning is a sudden spark, or electrical discharge ◦ Positive and negative charges jump between parts of a cloud, or between nearby clouds, or between a cloud and the ground Thunderstorms ◦ Lightning heats the air to 30,000oC ◦ Thunder is the sound of the rapidly heated air expanding suddenly and explosively ◦ Light travels faster than sound so you see lightning before you hear thunder Lightning Strikes in the U.S. ◦ This map shows how often lightning strikes different parts of the lower 48 states. Central Florida has the most intense concentration of cloud-to-ground lightning because it has a lot of warm, humid air. The Pacific Northwest has almost no lightning. Thunderstorm Safety ◦ Go INSIDE! ◦ Do NOT touch anything that can conduct electricityespecially metal objects and bodies of water ◦ Crouch down in a low area-avoid trees Tornadoes ◦ A tornado is a rapidly whirling, funnel-shaped cloud that reaches down from a storm cloud to touch Earth’s surface Tornado Formation ◦ Warm, moist air flows in at the bottom of a cumulonimbus cloud and moves upward ◦ A low pressure area forms inside the cloud ◦ Warm air rotates as it meets winds blowing in different directions at different altitudes ◦ Tornado Alley is an area of the United States that has a high frequency of tornadoes because cold, dry air moves south from Canada to meet warm, humid air from the Gulf of Mexico ◦ 5 states that cross Tornado Alley are: ◦ ◦ ◦ ◦ ◦ Texas Oklahoma Kansas Nebraska Iowa The Fujita Tornado Damage Scale ◦ Tornadoes are ranked on the Enhanced Fujita scale by the amount of damage they cause. Tornado Safety ◦ A tornado watch is an announcement that tornadoes are possible in your area. Stay tuned to the radio or television news. ◦ A tornado warning is an announcement that a tornado has been sighted. Take shelter immediately! ◦ The safest place to be during a tornado is in a storm shelter or the basement of a well-built building ◦ If you cannot get underground, go the center of the lower level and stay away from windows and doors. Hurricanes ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ A hurricane is a tropical cyclone that has winds of 119 km/h or higher Hurricanes form in the Atlantic, Pacific, and Indian Oceans In the western Pacific Ocean, hurricanes are called typhoons A hurricane begins over warm ocean water as a low-pressure area, or tropical disturbance. A hurricane draws its energy from the warm, humid air at the ocean’s surface As the air rises and forms clouds, more air is drawn into the system Inside the storm are bands of very high winds and heavy rains Winds spiral inward toward the area of lowest pressure at the center Hurricane Names ◦ Hurricanes are given names to help us identify them and track them as they move across the ocean ◦ Men and women's names are used ◦ One name for each letter of the alphabet except Q, U, and Z ◦ World Meteorological Organization uses six lists in rotation ◦ The only time a new name is added is if a hurricane is very deadly or costly ◦ If that happens then the name is retired and a new name is chosen. Hurricane Formation Hurricanes ◦ Hurricanes last longer than other storms, usually a week or more. ◦ After a hurricane passes over land, it no longer has warm, moist air to draw energy from so it loses strength. ◦ A storm surge is a “dome” of water that sweeps across the coast where a hurricane lands. ◦ For safety during a hurricane, people are told to evacuate. ◦ Evacuate means to leave the area immediately. Tornado Alley Worksheet ◦ Worksheet and map ◦ Worst Tornados in History ◦ Tornado Rampage 2011 ◦ Find some type of hurricane activity and add here Culture- Myths ◦ In the past, people from many cultures interpreted the weather as signs from the gods. Angry gods might send lightning to strike a person or place. ◦ Some Native Americans believe that giant birds called thunderbirds beat their wings to produce thunder. The flashing of their eyes creates lightning. ◦ An ancient Chinese myth tells how a thunderstorm is created by different gods. The thunder god is helped by Mother Lightning. She produces lightning using mirrors in her hands. The Master of the Rain sprinkles water from his pot with a sword. The Little Boy of the Clouds, piles up the clouds, while the Prince of Wind releases winds from a bag. ◦ According to Kenyan legend, God creates two rainbows, one male and one female, which must work together to stop the rain. It's raining cats and dogs ◦ According to the Library of Congress, the true origin of the phrase is unknown. Some popular ideas about the origin of the phrase include references to Norse and Greek mythology. ◦ Witches, which were associated with black cats, and the Norse god of storms, which was associated with dogs, may have been an early reference to storms. dogs" may refer to a storm with wind (dogs) and heavy rain (cats). ◦ Cata doxa, a Greek expression meaning "contrary to experience or belief" may have meant it is raining unusually hard. Weather Folklore ◦ Red sky at night, sailors delight; red sky in morning, sailors take warning. What does that mean? ◦ Winter weather folklore forecasting ◦ Weather Folklore Activity Sheet and poems Create your own myth ◦ Example - The Vikings believed thunder was caused by Thor. In Norse mythology, Thor was the god of thunder. He produces thunder with his hammer, called Mjolnir, which means "The Destroyer". This hammer was made by dwarfs, and would magically return to Thor's hand whenever he needed it. ◦ Create an original weather myth to explain some aspect of weather in words and in pictures. Video and Questions ◦ United Streaming: Hurricanes, Tornadoes and Thunderstorms – 24min. ◦ Video Questions and answers Characteristics of Weather ◦ Organize the characteristics into categories. ◦ Write down an explanation of how you organized the characteristics and why you categorized them that way. ◦ Share your categories and explanation with the class.