Severe Weather

--for those who know enough to come in out of the rain.

Flash flooding

Tornado

High winds

Lightning

Thunderstorm

Hurricane

Winter storms

• Over 500 Americans die each year due to weather related incidents.

• Billions of dollars of damage is done to American homes, farms, cities, and businesses

Rule 1

• Warm air tends to…

Rule 1

• Warm air tends to rise!

Just like warm water and warm magma

Convective uplift—it is forced up by the cooler (and therefore more

dense) fluid around it.

Four reasons air might rise:

1.

2.

3.

4.

Four reasons air might rise:

1. Convective uplift

2. Orographic uplift

3. Frontal wedging

4. Convergence

Four reasons air might rise:

1. Convective uplift

--less dense air is forced up by surrounding air 2. Orographic uplift

--if the land surface rises, the air has to rise 3. Frontal wedging

--an air mass forces its way under another mass 4. Convergence

--when two air masses come together, the only way to go is up

Air Masses

• --like water masses.

• A body of air with its own temperature and humidity

Air Masses

• --like water masses.

• A body of air with its own temperature and humidity

Continental (dry) or Maritime (humid)

Polar (cold) or Tropical (warm)

Front-where two air masses meet

• Cold air mass

(moving southeast)

Warm air mass

Cold air

mass

Warm air mass

(moving east)

Fronts

When a front advances…

When a front advances…

• …one air mass goes over the other.

• The warmer air mass usually goes over the other.

Clouds form…

Clouds form…• …when an air mass

cools enough to allow the water vapor to condense.

• When a warm air mass rises, it starts to cool due to expansion—air pressure is less up there

Cold Air mass

Clouds form…

• …or they don’t.

• Water vapor is clear and colorless--

Air has water vapor.

Clouds have water droplets.

Clouds form…

• …or they don’t.

• Water vapor is clear and colorless--

Air has water vapor.

Clouds have water droplets.

Condensation nuclei make it more likely that water vapor can condense into water droplets

Cumulus clouds make thunderstorms

Cumulonimbus clouds (raining)

Air movement in a thunderstorm

Types of clouds

• Basically—three types are important:

• Stratus

• Cumulus and

• Cirrus

Types of clouds

• Basically—three types are important:

• Stratus

• Cumulus and

• Cirrus

means “a layer”

means “heaped”

means “wispy”

Types of clouds

• Basically—three types are important:

• Stratus

• Cumulus and

• Cirrus

Nimbus = “raining”

Alto = “high”

Combination types take both names

Typ

es o

f cl

ou

ds

Types of clouds

Cirrus clouds

Stratus clouds

Cumulus clouds

Cumulonimbus

CumulonimbusComplete numbskull

Above the clouds

Above the

clouds

Weather occurs in the troposphere

Above the

clouds

Air cools as you get higher

Above the

clouds

Top of Mt. Everest

Above the

clouds

The tropopause is the top of the troposphere

Above the

clouds

Highest clouds

Above the

clouds

Passenger jets fly here

Above the

clouds

Propeller plane altitude

record

Above the

clouds

Jet plane altitude record

Above the

clouds

Air doesn’t get cooler

with altitude in the

stratosphere

Above the

clouds

Ozone layer

Above the

clouds

Cooling with altitude, again

Above the

clouds

NASA gives astronaut’s

wings above the

mesopause

Above the

clouds

Northern lights