Understanding Thunderstorms and Tornadoes

What happens to warm, moist air when it rises?

It expands and cools due to the expansion.

What forms when a cold air mass collides with a warm, moist air mass?

Cumulonimbus clouds.

Which is heavier: dry air or moist air?

Dry air is heavier than moist air.

What causes lightning?

A strong separation of electric charges occurs as falling ice particles strip rising water molecules of their electrons.

What causes thunder?

A lightning bolt raises the temperature of air to over 50,000°F, causing rapid expansion that results in a shock wave we hear as thunder.

How does hail form?

Hail forms when updrafts in thunderstorms are strong enough to repeatedly carry water droplets above the freezing level.

What distinguishes supercells from other thunderstorms?

Supercells can form a mesocyclone, which focuses rotation into a very tight rotation.

How does a supercell develop?

A supercell forms when strong vertical wind shear leads to a horizontal vortex that is then rotated into a vertical vortex.

What is the role of cold dry air and warm moist air in supercell formation?

Cold dry air from the north collides with warm moist air from the Gulf to form cumulonimbus clouds.

What effect do winds from the jet stream have on cumulonimbus clouds?

They cause the clouds to experience horizontal shear (vortices parallel to the ground).

What happens to warm dry air from the southwest in supercell formation?

It lifts and rotates the vortices into a vertical orientation, generating a spinning supercell.

Which way do winds blow near a tornado?

Near the ground, winds blow toward a tornado, feeding the strong updraft.

What happens to wind about 100 feet above a tornado?

Wind blows outward from a tornado.

What are the major components that make the Midwest productive for tornadoes?

The Midwest has cold dry air from the north and warm moist air from the Gulf, which collide to form cumulonimbus clouds.

How many tornadoes occur each year in the U.S.?

About 1000 tornadoes per year.

When is the prime tornado season in the U.S.?

The prime tornado season varies but generally occurs in spring and early summer.

How does the Enhanced Fujita Scale rate tornadoes?

It rates tornado strength based on the damage, which is used to estimate wind speed.

Can fixed Doppler radar easily measure tornado wind speeds?

No, fixed Doppler radar can only measure wind speeds a few kilometers above the ground.

Do tornadoes often contain multiple vortices?

Yes, multiple vortices are common, each rotating about a larger tornadic center.

Where should you take shelter from a tornado if stuck in traffic?

Get to a low spot (ditch or culvert) and lie down to avoid flying debris.

What is the biggest danger from tornadoes?

Flying debris.

What should you NOT do if caught in a tornado while under an overpass?

Do not hide under an overpass.