Severe Weather Storms Thunderstorms

Tornadoes Hurricanes

What are Thunderstorms?

Thunderstorms are severe storms from cumulonimbus clouds.

Tornadoes grow from thunderstorms.

Lightening is a result of electric sparks from storms. It gives off noise – thunder.

Lightning and thunder happen at the same time.

We see lightning before thunder because light travels

faster than sound.

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Stages of a Thunderstorm – STAGE

1

Air rises quickly due to intense heating – Updraft

More and more warm, moist air rises making the cloud grow bigger and bigger.

When updrafts can’t keep water in, it falls as heavy rain or hail.

STAGE 2

 

As the rain falls, it causes air to move downward – downdraft.

As the air goes up it rubs against the air going down, static electricity builds up creating sparks or lightening.

Lightening jumps all around; cloud to ground, ground to cloud, between two thunderclouds, different spots on one cloud.

Lightening slams around creating thunder.

STAGE 3 When the downdraft

becomes stronger than the updraft, heavy rain lightens up and stops.

Thunderstorms

Thunderstorms are more likely when it has been hot and humid and a cold front is approaching.

Thunderstorm Outdoor Safety Tips Go to a safe place immediately (a sturdy

building or car) Stay away from trees. If there’s no shelter, crouch down in an

open area. Stay out of water. Don’t stand in puddles. Avoid metal objects. Wait at least 30 minutes after the last

observed lightning strike or thunder before going back outside.

How and Where Do Tornadoes Happen?

THE MOST VIOLENT STORMS! It is a violent, whirling wind that moves across the

ground in a narrow path. When an updraft in a convection cell is VERY

strong, the air rushes in from all sides at varying speeds.

Form where dry, cold air masses MIX with warm, moist air masses.

The air curves and spins. Air rushes in fast, lowering the pressure.

It gets faster and faster.

Tornadoes In the center of the tornado,

winds can be up to 300 miles per hour!!

Their direction can change at any moment.

Where they Occur In the Midwest and the south are the

most commonly seen. Great Plains, Mississippi Valley &

Florida Most often in early spring and the

summer. Waterspouts are tornadoes that form

over water.

Tornado Safety Tips Go to a basement. If you don’t have a basement, go to an

interior room on the lowest floor (ex. a bathroom or closet)

Get under sturdy furniture Stay away from windows. If outside, go to a ditch or low lying area

and lie flat.

How Do Hurricanes Form? Hurricanes are very large,

swirling storms with very low pressure in the center. What does that mean for the high pressure outside?

They form over tropical oceans – near the equator.

Formation of Hurricanes A large, low-pressure center forms over the

ocean because of a lot of heating and evaporating here.

Then, winds blow IN toward the LOW pressure. As it rushes in and upward, a tall ring of thunderstorms form.

Because of the Coriolis Effect, the winds spiral counterclockwise.

Thunderstorms are pulled into the spiral. They ALL merge into ONE, LARGE storm.

Formation of Hurricanes

As the water vapor in the air condenses, heat is released.

As a result, air density and pressure is lowered.

Low air pressure favors evaporation. The lower the air pressure, the faster the

winds that are blowing toward the center. When the winds reach about 75 miles per

hour or higher, we have a hurricane.

Formation of Hurricanes cont’d.

As the moist air in the storm rises and cools, condensation takes place.

As a result, clouds thicken and heavy rain falls.

When fully formed, a hurricane has an eye at the center.

The eye is an area of light winds and skies that are nearly clear.

How Do Hurricanes Affect Ocean Waves?

As hurricanes move north away from the equator, their speeds increases.

Hurricanes create large waves in the oceans. The waves pound on the shore even BEFORE the

hurricanes arrive. The storm surge, great rise of the sea along the

shore, causes the most destruction. When the pressure of a hurricane drops, the

surface of the sea rises forming a bulge beneath the hurricane.

How Do Hurricanes Affect Ocean Waves

cont’d. When hurricanes move over a coast, the bulge can cause water levels to rise several feet (surge).

During a great storm, the surge, large waves, high winds, and torrential rain of the storm happen at the SAME time.

In effect, low-lying coastal areas become flooded.

Hurricanes die out when they move over land because they have no water from the ocean.

What Can You Do to Be Safe in a Hurricane?

Have a disaster plan ready and prepare an emergency supply kit.

Board up windows and bring in things from outdoors that might blow away.

Be prepared to evacuate when necessary.

Listen to weather storm advisories.

How Can Radar Track Storms?

Storms are harder to predict because of how quickly they form.

Doppler Radar is used to find storms as they form.

Radar works by sending out radio waves and recording their echo.

Differences in the echo at different times help predict weather patterns and how often or frequent those echoes are occurring.