metro correct 3

Thunderstorms

• Formation of thunderstorms?

o When warm, humid air rises

• What are the different types of thunderstorms? Describe them and their

characteristics.

o Air mass thunderstorm: Air rises due to unequal heating of surface

o localized, short lived

o Severe thunderstorm: caused by rapid uplift of warm humid air along a front

or mountain range

o high winds, hail, flash floods, possible tornadoes

o Supercell thunderstorm: Type of thunderstorm that consists of single,

persistent, and very powerful cell (updraft and downdraft) and produces

severe weather (hail, high winds, tornadoes)

o Up to 65,000 ft high, diameter between 12-30 miles, rotates forming a

mesocyclone

• How many thunderstorms occur daily worldwide?

o 45,000

• How does lightning form?

o Caused by separation of charges; ice pellets develop a positive outer shell

and a negative nucleus. As they expand and shatter, positive pieces of shell

rise to the top of cloud• What percentage of lightning stays within the clouds and what percentage touches

the ground?

o 80% is sheet lightning

o 20% reaches the ground

• How does thunder form?

o Thunder is caused by the rapid expansion of air surrounding the extremely

hot lightning bolt (33,000°C)

• How do you measure distance to lightning?

o 5 second difference between lightning and thunder = 1 mile distance to

lightning

• What are some safety precautions for thunderstorms?

o Stay in a car

o Stay indoors and close all windows

o Don’t turn on water

o Don’t wave metal in the air

o Lay low

Tornadoes

• Define tornado

o Violent wind storm in the form of rotating columns of air (vortex)

• Where do tornadoes form?

o In a thunderstorm or along fronts

• What is a mesocyclone?

o The precondition for tornadoes

• List the steps of a tornado formation.

o Air rises rapidly at surface

o High winds aloft create a horizontal rotation of airo Strong updrafts tilt the rotation vertically

o Mesocyclone extends vertically and drops below cloud base and rotates

slowly (wall cloud)

o Thin, rapidly spinning vortex extends downward (funnel cloud) and if it

reaches the surface it’s a tornado

• When and where do tornadoes occur the most?

o Between April and June

o In the midsection of the U.S. (cP air from Canada collides with mT air from

Gulf)

• What is the diameter of a tornado?

o 500-2,000 ft

• The average speed?

o 30 mph

• How far do they usually travel?

o 16 miles

• In what direction do most tornadoes go?

o Northeast

• How long does the average tornado last?

o Less than 3 minutes

• List the Fujita Intensity Scale

o EF0 = 65-85 mph

o EF1 = 86-110 mph

o EF2 = 111-135 mph

o EF3 = 136-165 mph

o EF4 = 166-200 mph

o EF5 > 200 mph

• What is a Doppler Radar?o It shows the circular motion of air and can detect motion leading to

mesocyclone and tornado formation