Thunderstorms and Tornadoes

1. What happens to warm, moist air when it rises?

It forms cumulonimbus clouds. When the Warm, moist air rises, expands, and cools.
Cooling causes condensation of the water vapor forming cloud droplets and ice crystals.
This process forms cumulonimbus clouds which are associated with the biggest storms.

2. What happens when a cold air mass collides with a warm, moist air mass?

It creates a weather front, almost always a cold front. The Cold, dry air pushes warm, moist air upward rapidly.
This rapid lifting forms cumulonimbus clouds which are associated with strong thunderstorms.
Strong thunderstorms often develop along cold fronts.

3. Which is heavier: dry air or moist air?

Dry air is heavier than moist air. And cold air tends to be dry because it cannot hold much moisture. Therefore dry air is heavier than moist air and cold air is heavier than warm air.

4. What causes lightning, thunder, and hail?

Lightning is caused by a sudden electrostatic discharge between oppositely charged regions.
Thunder is a shock wave caused by lightening over 50000F resulting from air suddenly rapidly expanding after being heated by lightning
Hail forms when strong updrafts repeatedly lift ice crystals above the freezing level until it becomes too heavy and falls.

5. What distinguishes supercells from other thunderstorms and how do they develop?

Supercells are the only thunderstorms capable of producing strong tornadoes because they contain a rotating updraft called a mesocyclone.
They form when wind shear creates horizontal rotation that becomes vertical.
This rotation can tighten and produce a tornado.

6. Which way does the wind blow near a tornado?

Near the ground, winds blow inward toward the tornado.
About 100 feet above the ground, winds blow outward.

7. Why is the Midwest productive for tornadoes, how many occur, and when is peak season?

Why the Midwest is ideal

• Cold, dry air from the north collides with warm, moist air from the Gulf of Mexico.

• The jet stream creates horizontal wind shear.

• Warm, dry air from the southwest lifts and rotates vortices vertically.

How many tornadoes

• About 1,000 tornadoes occur each year in the U.S.

Peak season

• Spring, when Gulf waters warm while cold air still moves south from the north.

8. How does the Enhanced Fujita Scale rate tornadoes?

The EF Scale rates tornadoes based on damage.
Damage is used to estimate wind speed.
Ratings range from EF0 to EF5.

9. Can fixed Doppler radar easily measure tornado wind speeds?

No, tornado wind speeds are difficult to measure.
Fixed Doppler radar measures winds several kilometers above the ground.
This works for supercells but not tornadoes.

10. Can tornadoes contain multiple vortices?

Yes, tornadoes can contain multiple vortices.
These vortices rotate around a larger tornadic center.
Tornadoes cannot split or merge.

11. Where should you take shelter from a tornado and what is the biggest danger?

Shelter in a basement or small interior ground-floor room without windows.
If in a car, lie flat in a low ditch and never hide under an overpass.
The biggest danger from tornadoes is flying debris which come at you from the side not above you.