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