Transcript Storms!
Storms! Coulter Thunderstorms • Storm is a violent disturbance in the atmosphere. • Thunderstorm is a small storm often accompanied by heavy precipitation and frequent thunder and lightning. • Thunderstorms form in large cumulonimbus clouds, also known as thunderheads. How thunderstorms form • Cumulonimbus clouds form on hot, humid afternoons. • They also form when warm air is forced up by cold fronts. • In both cases, the warm, humid air rises rapidly. The air cools, forming dense thunderheads. • Within a thunderhead are strong upward and downward winds. Lighting and thunder • Lightning is a sudden spark, or electrical discharge, as these charges jump between parts of a cloud, between nearby clouds, or between a cloud and the ground. • It is similar to when you get shocked when touching a metal object or somebody else, but on a much larger scale. • Lightning bolts can heat the air near it to as much as 30,000 C, much hotter than the sun’s surface. • The thunder sound is the explosion from the lightning. • Because light travels faster than sound you see it before you hear it. Lightning distance • Here is how to calculate the distance from a thunderstorm. • Count the number of seconds between the moment you see the lightning and when you hear the thunder. • Divide the number of seconds you counted by three to get the approximate distance in km • Example: if you counted 15 seconds, you would say 15/3= 5km Thunderstorm damage • Heavy rains can flood low-lying areas. • Lightning can cause damage; shatter tree trunks, start forest fires, can cause unconsciousness in people/animals, serious burns, and even heart failure. Floods • Floods occur when so much water pours into a stream or river that its banks overflow, covering the surrounding land. • A flash flood is a sudden, violent flood that occurs shortly after a storm. Thunder safety • During a thunderstorm, avoid places where lightning may strike. Also avoid object that can conduct electricity, such a metal objects and bodies of water. Tornadoes • Is a rapidly whirling, funnel-shaped cloud that reaches down from a storm cloud to touch Earth’s surface. • If a tornado forms over a lake or ocean it is known as a waterspout. • Tornadoes are usually brief, may only last for 15 minutes. How tornadoes form • Tornadoes most commonly develop in thick cumulonimbus clouds– the same clouds that bring thunderstorms. • Most likely to occur in spring and early summer. Late in the afternoon when the ground is warm. • A warm, humid air mass moves north from the Gulf of Mexico into the lower Great Plains. A cold, dry air mass moves south from Canada. When the air masses meet, the cold air moves under the warm air, forcing it to rise. • The varying winds at different heights can spin the rising air like a top. Tornado formation • http://news.bbc.co.uk/2/hi/5328524.stm Tornado alley • Tornadoes occur more often in the U.S. than in any other country. • About 800 tornadoes occur in the U.S. every year. Tornado damage • Tornado damage comes from both strong winds and flying debris • Low pressure inside the tornado sucks dust and other objects into the funnel. • Tornadoes can move large objects; sheds, trailers, cars, and scatter debris many miles away. • One tornado tore a hotel sign out of the ground in Oklahoma and dropped it 30 miles away in Arkansas. • They are unpredictable. • Tornadoes are ranked on the Fujita scale (named after Dr. T. Fujita) o Light damage F0, to extreme damage F5. Only about 1 percent of tornadoes are ranked as F4 or F5 Tornado safety • The safest place to be during a tornado is in a storm shelter or the basement of a well-built building. • If no basement is available move to the middle of the ground floor. • Stay away from windows and doors. • Lie on the floor under a sturdy piece of furniture, such as a large table. • If you are outside lie flat in a ditch. Write and research • Many of these events happened before forecasters had the equipment to predict weather scientifically. Research one of the events in the timeline. White a paragraph describing the event and how history might have been different if the people involved had had accurate weather predictions. o o o o o o o 1281 Japan 1588 England 1620 Massachusetts 1837 North Carolina 1870 Great Lakes 1900 Texas 1915 Texas