Severe Storms

Thunderstorms• Thunderstorms are large

cumulonimbus clouds that have lightning and thunder that occur within and around the cloud

• Two of the most important ingredients for thunderstorm formation are – instability (unstable air) –air

continues to rise when given a nudge upward (or continues to sink if given a nudge downward

– moisture.

http://www.youtube.com/watch?v=I8OEEhKlKzE

Thunderstorms• Formation

– When air is lifted, the moister in the air rises and condenses

– Water droplets in the clouds continue to grow larger and build

– When the droplets are too large the fall to the ground as precipitation

• Thunderstorms are most common in NC during spring and summer months

Tornadoes• A tornado is a violently

rotating column of air in contact with and extending between a cloud (often a thunderstorm cloud) and the surface of the earth

• Abundant low level moisture is necessary, and a "trigger” that lifts the moist air is needed for the development of tornadoes and the thunderstorm cloud.

• Tornadic phenomena can take several forms

• Formation– A change occurs in wind direction

and speed within the thunderstorm itself

– This change happens high in the cloud and creates an invisible shearing affect in the atmosphere

– Rising air cools in the thunderstorm and the rotating winds upright and lower a wall of clouds to the ground

– Once the touchdown occurs, the energy of the storm will continue until the air in the cloud disperses and the tornado in essence dies.

Tornadoes usually form in areas where winds at all levels of the atmosphere are not only strong, but also turn with height in a clockwise, or veering, direction

Hurricanes• Tropical cyclones can develop in

the Gulf of Mexico, the Caribbean Sea, the Pacific and Atlantic Oceans.

• Hurricane season in the Atlantic lasts from June-November

• Tropical cyclones need heat and moisture to form

• Storms that form north of the equator spin counterclockwise. Storms south of the equator spin clockwise. http://

video.nationalgeographic.com/video/environment/environment-natural-disasters/hurricanes/katrina-formation/

• Hurricane Formation: – Air from surrounding areas with higher

air pressure pushes in to the low pressure area.

– The "new" air becomes warm and moist and rises, too.

– As the warm air continues to rise, the surrounding air swirls in to take its place.

– As the warmed, moist air rises and cools off, the water in the air forms clouds.

– The whole system of clouds and wind spins and grows, fed by the ocean's heat and water evaporating from the surface.

– As the storm system rotates faster and faster, an eye forms in the center. It is very calm and clear in the eye, with very low air pressure. Higher pressure air from above flows down into the eye.

STORM DESTRUCTION

Thunderstorms• In a thunderstorm, you will find

lightning and thunder. – Lightning is an electrical discharge

that balances the difference between positive and negative charges within a cloud, between two clouds, or between a cloud and the ground.

– Thunder is an explosion of noise heard when atmospheric gases are suddenly heated by a discharge of lightning.

• There can be as many as 40,000 thunderstorms each day around the world. They are most common in the U.S.

Thunderstorms• Thunderstorms can cause

flash floods and fires.• People can suffer from

lightening strikes– Number of fatalities per

year (30-year average 1980-2009): 57 (Ties with tornadoes and is more than those with hurricanes)

– Florida is the most lightening prone state

Tornadoes• Tornadoes are rare, unpredictable

and deadly. • The U.S. has more tornadoes than

anywhere else in the world• Tornados typically track along the

ground for a few miles or less and are less than 100 yards wide.

• Winds in most tornadoes blow at 100 mph or less, but in the most violent, and least frequent tornadoes, wind speeds can exceed 250 mph.

http://www.youtube.com/watch?v=7EV87q093ow

Tornados

• Most damage from a tornado comes from flying debris

• Because there are few actual measurements of tornado winds, their intensity is estimated through after-the-fact examination of the damage that they produced. Prior to February 2007, that was done using the Fujita Scale (F Scale). Since then, the National Weather Service has adopted an Enhanced Fujita Scale (EF-Scale) to rate tornadoes.

Joplin Tornado

http://www.youtube.com/watch?v=eADXmGukZiE

Hurricanes• Tropical cyclones or hurricanes usually

weaken when they hit land, because they are no longer being "fed" by the energy from the warm ocean waters.

• They often move far inland, dumping many inches of rain and causing lots of wind damage before they die out completely.

• A storm surge, a wall of water that builds up over the ocean because of heavy winds and low atmospheric pressure, causes the coastal regions to be flooded.

• Can cause groundwater pollution and damage of infrastructure from flooding and wind damage.

Superstorm Sandy- NJ

Hurricane Irene-NC

Sandy Storm Surge: http://www.youtube.com/watch?v=UnkueRbwPsIHurricane Irene:http://www.youtube.com/watch?v=sVbLpTu_egg

Storm Prevention• These severe storms can

bring wind, heavy precipitation, and lightening.

• Storm Preparation– Flood/storm walls– Moving buildings– Raised/reinforced buildings– Storm shelters – Government Actionhttp://www.youtube.com/watch?v=vFM98okhyss

Severe Storm Writing Prompt

• Which of the severe storms do you think is the destructive? Why?– Standard: Give three reasons (1 paragraph)– Honors: Give five reasons (at least 1 page)

• What can you do to prepare for this severe event? What can the government do?– Can do in a bulleted format