Clouds & StormsCh. 23 & 24

SOL 13 The student will investigate and understand that energy transfer between the sun and the Earth and its atmosphere drives weather and climate on Earth. Key concepts include severe weather occurrences such as tornadoes, hurricanes, and major storms;VBO: 3.4.5Describe the cause and effects of destructive storms such as severe thunderstorms, hurricanes, tornadoes, monsoons, and winter storms including the proper precautionary steps to be taken.

Cloud Formation• Cloud: small collection of water droplets or ice

crystals that form when condensation or crystallization occurs more rapidly than evaporation or sublimation does.

• Condensation Nuclei: Suspended particles that provides the surface necessary for water vapor to condense. Usually are particles of ice, dust or salt.

Classification of Clouds:based upon their shape and altitude

Latin Vocabulary Check• Cumulo = piled or heaped• Stratum = layered• Cirro = hair or curl• Nimbus = rain• Altus = high

Stratus• Sheet like or layered• Low clouds, covers large areas of the sky and

blocks sun, little precipitation• Stratus cloud on the ground is known as fog

Nimbus

• Very dark, cause heavy precipitation

Cumulus Family• Cumulus: Resemble cotton balls with a dark

bottom, no precipitation• Cumulonimbus: dark storm clouds, known as

thunderheads, accompanied by rain, lightning and thunder

Cirrus• Composed of ice crystals • highest altitude• Commonly appear just before a snowfall or rainfall• A halo appears around the sun or moon when

viewed through a cirrus cloud. Halo is formed by the refraction of light rays through ice crystals

3-2-1 with your shoulder partner:

Describe conditions related to 3 cloud types:List 2 Latin names used in cloud classification:How might an increase in 1 form of pollution (ash

particles from forest fire or volcanic eruption) affect cloud formation?

Storms

Watch or Warning?

• Storm Watch: conditions are favorable for the storm to develop

• Storm Warning: warns of approaching dangerous weather. Take cover and follow safety guidelines.

Cyclones and Anticyclones?• Cyclones – area of low pressure containing rising warm air.

Air currents start to spin. In the Northern hemisphere they go counterclockwise and cause rainy stormy weather.

• Anticyclones – high pressure area with cold, dry air. Causes dry clear fair weather. In the Northern hemisphere they move clockwise.

The closer the isobars the windier it is

Types of storms• Storms – a violent disturbance in the atmosphere. Marked

by sudden change in air pressure and rapid air movement.• Most common are rain and snow storms – occurs when two

fronts collide (cold meets warm)Summer = steady rain, ThunderstormsWinter = heavy snowfall, Blizzard = wind must reach

36 km/hr and be -7 degrees Celsius. Ice storm = rain freezes instantly causing damage due to weight on objects

Thunderstorms• Cold front meets warm front forming heavy rainstorms with

thunder and lightning, violent down drafts and strong wind shear.

• May contain straight line winds (downburst): colder air being forced down vertically in front of a storm. Once the downburst hits the ground it has nowhere else to go, and is forced along the ground at great speed.

• Straight-line wind damage will push debris in the same direction the wind is blowing (hence the term straight-line).

Lightning• Lightning – sudden discharge of electricity between

cloud and cloud; cloud and ground.• When the air is heated by lightning it expands quickly

resulting in loud sound waves (thunder).• Leading cause of forest fires. Can strike people,

animals, or building.• Safety – avoid open spaces outside; don’t go under

trees for shelter, avoid sinks, bathtubs, televisions, and telephones while inside during a lightning storm.

Hurricanes and Typhoons• Hurricanes – tropical cyclone that forms over tropical areas.• Typhoon – hurricane that forms over the W. Pacific ocean.• rapidly, spinning rising air forms a donut-shaped

wall of strong winds, clouds, and rainfall. • The eye of the storm is calm. • The wind reaches speeds of 74 to over 155 m/hr.

May cause serious flooding. • Typical hurricane lasts for about 9 days and can last

for up to 3 or 4 weeks.

Most powerful of all storms.

Map of a hurricane

How are hurricanes categorized?

Remind me to show you the Hurricane Katrina before/after PPT

Anatomy of a Hurricane

Hurricane SafetyKnow the hurricane risks in your area. Learn the storm surge history and

elevation of your area. Learn safe routes inland. Learn the location of official shelters. Ensure that enough non-perishable food and water supplies are on hand. Have at least a one week supply of medications on hand. Obtain and store materials, such as plywood, necessary to properly secure

your home. Clear loose and clogged rain gutters and downspouts. Keep trees and

shrubbery trimmed of dead wood. Review your insurance policy. Make plans now on what to do with your pets should you be required to

evacuate your residence.

Tornadoes• Destructive whirling, funnel-shaped cloud. • Develops in low, heavy cumulonimbus clouds. • Acts like a giant vacuum cleaner, due to the low

pressure. • Form usually in the spring in late afternoons/

evenings.

Most common in the United States.

Map of a tornado…

More about tornadoes…• Great Plains known as “tornado alley”• Average diameter - .4 km• Length traveled – 6 km for only a few minutes but winds

can still reach more than 350 km/hour.• Houses, trains, cars, and people can all be thrown 100’s of

meters.• Measured on the Fujita scale as F0 – F5. (five being the

strongest).• Waterspout: Tornado in water, least damaging

Tornado alley

Debris scatters all directions

Tornado during sunny weather

Copy and turn in for a grade 1. Explain the conditions necessary for storms to form:2. The relation between thunder and lightning is:3. How are cyclones and anticyclones different?4. A typhoon requires these conditions in order to form:5. Tornadoes of the greatest strength measure what on the fujita scale?6. Where is tornado alley?7. How are watches and warnings different?8. How can a scientist interpret whether a straight-lined wind or

tornado has caused damage? 9. Optional: Do you have any additional questions or observations that

you would like to state?