Chapter 20 Section 3Thunderstorms and Tornadoes

Objectives:-Describe the conditions necessary for the formation of thunderstorms and tornadoes

-Describe the hazards of thunderstorms and tornadoes, and discuss related safety measures

Thunderstorms:

• Storms with lightning, thunder, rain, hail• Only few kilometers in size• Cumulonimbus Clouds (see page. 396-399 and

describe the features of this type of cloud)• Typically occur during the afternoon– Why?

– Surface warming during the day causes air to become unstable

Squall Lines

• Thunderstorms that occur in lines ahead of fronts

• Associated with heavy winds and rain.– Storms move slowly and can lead to flooding

– What will temperatures do after this front passes?

Radar Image of a Squall Line.What part of the country?

Supercells

• Very large single-cell thunderstorms with strong updrafts.

• Can develop into tornadoes

Look familiar?

Lightning

• Discharge of electricity from;– cloud to ground,– to another cloud, – or to another spot within the same cloud.

Tornadoes

• Rotating column of air can be associated with thunderstorms.

What trend is represented?

Fujita Tornado Intensity Scale