Severe WeatherA SCIENTASTIC PRESENTATION
Storm Chaser’s Clip
http://www.discovery.com/tv-shows/storm-chasers/videos/what-is-the-dominator.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 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
A squall line is a line of severe thunderstorms that can form along and/or ahead of a cold front.
Super cellsSuper 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 CellsComponents 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/science-experiments+10/how-to-make-a-cloud-in-a-jar+12511.htm
TornadosTornadoes 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/science-experiments+10/tornado-in-a-jar-experiment+12759.htm
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