Severe Weather
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Severe Weather A SCIENTASTIC PRESENTATION Storm Chaser’s Clip http://www.discovery.com/tv-shows/storm-chasers/videos/what-is-thedominator.htm Discussion Question – Severe Thunderstorms Capable of producing: heavy downpours and flash flooding Strong, gusty straight-line winds Large hail Frequent lightning Tornadoes For a thunderstorm to be officially classified as severe: winds in excess of 93 kilometers (58 miles) per hour produce hailstones with diameters larger than 1.0 inch or generate a tornado. about 10 percent (10,000 storms) reach severe status. Life Cycle of Thunderstorms Cumulus Stage Dominated by rising currents of air (updrafts) Formation of a towering cumulonimbus cloud Falling precipitation within the cloud causes drag on the air and initiates a downdraft The downdraft is called an entrainment Life Cycle of Thunderstorms Mature Stage Downdraft leaves the base of the cloud and this releases the precipitation Gusty winds, lightning, heavy precipitation, and sometimes hail The most active period of a thunderstorm. Life Cycle of Thunderstorms Dissipating Dominated by downdrafts Without a supply of moisture from updrafts, the cloud soon evaporates Squall Lines A squall line is a line of severe thunderstorms that can form along and/or ahead of a cold front. Contains heavy precipitation, hail, frequent lightning, strong straight line winds, and possibly tornadoes and waterspouts Form in unstable atmospheric environments where low-level air can rise Heat is released during condensation Causes the rising air becoming lighter than nearby air at the same height. This leads to an increase in the speed of the rising air (up to 30 mph) The gust front where these winds meet extends from the surface well up into the storm Super cells Super cell is a large rotating thunderstorm with a mesocyclones Can last longer than normal thunderstorms Can produce tornadoes and baseball size hail. Mesocyclone is a large rotating vortex of air Rotate in the same direction as a low air pressure system Formed when wind shear starts a portion of air in the lower atmosphere spinning in a tube In the tube the air is rotating around a vertical axis. Super Cells Components of a Supercell The overshooting top is a dome shaped formation on the top of a supercell The anvil is the overshooting portion at the top of the supercell (cold, dry) The precipitation free base is a portion of the supercell without precipitation The wall cloud is the portion of the super cell between the precipitation free base and precipitating areas Lab – Make Your Own Cloud http://www.kidspot.com.au/kids-activities-and-games/scienceexperiments+10/how-to-make-a-cloud-in-a-jar+12511.htm Tornados Tornadoes are large clouds mostly characterized by extremely high winds Usually found in the most intense super cells and are caused by winds traveling in different directions Look like large funnels touching down from the main cloud A funnel cloud may or may not occur with a tornado Damage caused by a tornado can be related to the high Hazards include downed power lines, broken gas lines and pumps, and fires Formation of Tornados Formation The rotation of winds within a meso cyclone allows a vortex to form A funnel cloud usually forms Gains energy as it descends Becomes a tornado once it touches down Maturity When it becomes a tornado Where all the destruction comes in. Dissapation Meso cyclone loses its rotation Begins to dissipate Shape of the tornado can be altered Water Sprouts Waterspouts are similar vortexes that occur over water. They are usually less violent than regular tornadoes, although they can be rather powerful given a strong storm Fujita Scale An F6 category was also thought of, but it is purely hypothetical and no F6 tornado has actually existed. The Enhanced Fujita Scale was intended to improve the Fujita scale. Both scales measure the severity of tornados. Lab – Make Your Own Tornado http://www.kidspot.com.au/kids-activities-and-games/scienceexperiments+10/tornado-in-a-jar-experiment+12759.htm
