STORMS

A tornado is a violently rotating column of air

extending from a thunderstorm to the

ground

Change in wind directionIncrease in wind speedIncreasing heightRising air within a thunderstorm

Category Damage Wind

F0 light 40–72 mph

F1 moderate 73–112 mph

F2 significant 113–157 mph

F3 severe 158–206 mph

F4 devastating 207–260 mph

F5 incredible 261–318 mph

Tornado damage is measured by the

5

Where do Where do most tornadoes hit in the United States? tornadoes hit in the United States?

In the United States, the area where the tornadoeshit the most is called Tornado AlleyTornado Alley. The

states which are in the tornado alley are:

TexasNebraskaColoradoIowaIllinoisIndianaMissouriArkansas

Danger!Danger! Tornadoes!

What is a hurricane?

• Violent cyclonic storm that develops in the tropical region

• Wind speeds are > 74 mph

Source: http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=680

Rotation and Pressure

In which direction does a hurricane rotate?COUNTERCLOCKWISE

Is the barometric pressure inside the hurricane high or low?

LOW

What conditions must be present for a hurricane to develop?

1. Warm ocean temperatures (>80˚ F) up to 60m deep

2. Little to no wind shear

3. Low pressure system at least 5˚ North or South of Equator

4. Rotation caused by winds Source:

http://lwf.ncdc.noaa.gov/oa/reports/fran/

fran.html

What is the major source of energy fueling a hurricane?

Heat Energy evaporating from the ocean surface

Source: http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/evap.rxml

Hurricane Anatomy

Source: http://hurricanes.noaa.gov/prepare/structure.htm

By what two factors is hurricane strength measured?

Wind Speed

Barometric Pressure

What is the Scale Used to Categorize Hurricanes?

Saffir-Simpson ScaleCategory Max Wind Speed

(mph)

Min. Surface Pressure (mb)

Storm Surge m (ft)

1 74-96 > 980 1-1.7 (3-5)

2 97-111 979-965 1.8-2.6 (6-8)

3 112-131 964-945 2.7-3.8 (9-12)

4 132-155 944-920 3.9-5.6 (13-18)

5 > 155 < 920 > 5.7 (>19)

Source: http://kids.earth.nasa.gov/archive/hurricane/saffir-simpson.html

Thunderstorms and Rising Air

• Thunder storms are started when air rises, cools and starts to loose its moisture.

• T-storms are caused by rising humid air along either a warm or cold front

• The greater the temperature differences, the more quickly the storm forms

• T-storms are rather short-lived, usually the cycle lasts an hour or less

3 parts to a T-storm1. Formation – rising air expands & cools;

condensation occurs, clouds form

2. Mature – precipitation/bad weather

3. Dissipation – clouds disappear

1. A severe snowstorm with strong winds and poor visibility

2. Winds must exceed 56km (35 mi) per hour

3. Temperature must be -7 degrees celsius or lower

When do Blizzards Occur

• Blizzards occur anytime between late fall and early spring.

How do Blizzards Form

1. When colder air meets warmer air and begin to twist.

2. Some type of precipitation must be present in the clouds.

3. Must be a combination of freezing temperature and heavy winds.

Where Do Blizzards Occur

Blizzards are most common in the:

1. Northern Mississippi Basin

2. Central Part of Canada

3. Russia

4. Central Great Plains