Transcript Clouds, Air Masses, & Fronts

“Cloud Formation”
I. Cloud Formation:
A. Cloud- A collection of millions of tiny water drops in the
air.
B. Why are there clouds in the sky?
1. Clouds start to form when a parcel of warm moist air
starts to rise.
2. Parcel- A small contained area of air.
3. As the parcel gets higher it cools and expands.
4. Cold air can’t hold as much H2O as warm air.
5. The parcel will reach saturation eventually.
6. If the parcel of air reaches saturation, H2O will
condense onto any solid object. (Dust, salt, smoke, etc.)
7. If the parcel is allowed to keep on rising millions of
H2O drops condense onto this stuff.
8. That is when a cloud is formed.
II. Why do clouds form in certain areas?
A. Air can be stable or unstable.
1. Stable Air- When a rising parcel of air becomes cooler
than the air around it. .
A.) High Pressure
B.) If the air becomes stable it will sink.
C.) If that happens before the air is saturated, a cloud
will not form.
2. Unstable Air- When a parcel of air is warmer than the
air around it.
A.) Low Pressure
B.) If the air stays unstable it will continue to rise.
C.) If it reaches the saturation level it will form a
cloud.
III. Cloud Classification:
A. There are three main types of clouds.
1. Cirrus:
A.) Thin feather like clouds.
B.) High altitude.
C.) No precipitation.
D.) Can be a clue that a storm is approaching.
2. Cumulus:
A.) Thick puffy clouds.
B.) Some are cauliflower shaped.
C.) Thunderstorms and hail are come in some types.
3. Stratus:
A.) Light gray, thin layered clouds.
B.) Low altitude.
C.) Light precipitation in most types.
D.) Fog is an example.
B. Cloud Types:
1. There are five words that can be attached to the main
cloud types, to give them a more specific name.
A.) Cirro- High altitude clouds.
B.) Alto- Mid altitude clouds.
C.) Strato- Low altitude clouds.
D.) Nimbo & Nimbus- Very dark heavy rain clouds.
C. Examples:
1. Cumulonimbus:
A.) Cumulus cloud that grew into a very large, dark,
heavy rain cloud.
B.) This type of cloud is the heaviest rainmaker.
C.) Thunderstorms, and tornadoes are common.
2. Nimbostratus:
A.) Huge layers of dark., low altitude, rain clouds.
B. ) Very long periods of rain can fall from these
clouds.
I. High Clouds:
1. Cirrus
2. Cirrostratus
3. Cirrocumulus
II. Middle Clouds:
1. Altostratus
2. Altocumulus
III. Low Clouds
1. Stratus
2. Stratocumulus
3. Nimbostratus
IV. Clouds with
vertical development:
1. Cumulus
2. Cumulonimbus
IV. Precipitation:
A. There are 5 types of precipitation.
1. Rain-
Drops of H2O falling into areas of above
freezing temps..
2. Snow- H2O that falls as a frozen six sided, flake.
3. Sleet- Forms when snow falls through a warm area of
air, melts, then freezes back into an ice pellet.
4. Hail- Warm weather falling lumps of ice.
A.) Most commonly found in cumulonimbus clouds. .
B.) Water freezes in the upper level of the cloud, into
a small ice pellet.
C. ) When it falls it gets caught in the strong up drafts
of wind.
D.) The up drafts blow the ice pellet back into the
freezing temperatures.
E.) Another layer of ice forms around it.
F.) The process continues until the ice pellets are too
heavy for the up drafts.
G If the ice pellet does not melt before it hits the
ground you will see hail.
5. Freezing rain- Rain drops that are “super cooled”.
A.) Salt dissolved in rain lowers the freezing point of
H2O.
B.) As soon as it touches a solid surface it freezes to it
.
“Weather Patterns”
I. What causes our weather to change?:
A. The movement of different air masses causes weather to
change.
1. Air Mass- Large body of air that has the same
characteristics as the same area it formed
over.
B. There are four basic air massed that effect weather in
United States.
1. Continental Polar (cP)- Form over cold dry areas.
A.) cP air masses bring clear skies, and cold
temperatures.
B.) Come from Canada.
2. Continental Tropical (cT)- Form over warm dry areas.
A.) cT air masses bring clear skies and warm
temperatures.
B.) Come from Mexico.
3. Maritime Polar (mP)-
Form over cold wet areas.
A.) mP air masses bring cloudy skies and cold
temperatures.
B.) Come from the Northern Pacific, or the Northern
Atlantic.
4.Maritime Tropical (mT)- Form over warm moist areas.
A.) mT air masses bring cloudy skies and warm
temperatures.
B.) Come from the Gulf of Mexico. (Provides the
majority of moisture to eastern storms)
Blues
=cold/dry
Green
=cold/moist
Pink
=hot/moist
Red
=hot/dry
C. Why do air masses change
weather?
1. These four air mass types can be either stable or
unstable.
2. When two different air masses collide weather
changes may occur.
3. The boundary between the two air masses is called a
front.
II. Fronts:
A. What are fronts?
1. Front- The boundary between two different air
masses.
2. If air between the boundaries is unstable then clouds
will form and a storm may occur.
show me
B. There are four types of fronts:
1. Warm Front- Happens when a warm air mass moves
into a cold air mass.
A.) The warm air will rise over the cold air slowly.
B.) If the air is wet, clouds of the stratus and cumulus
variety will form.
C.) If the air is dry it will bring nice weather with
some high cirrus clouds.
D.) On a weather map they look like this:
Warm Air
Cold Air
2. Cold Front- Happens when a cold air mass moves
into a warm air mass.
A.) The cold air forces the warm air to rise quickly.
2. Cold Front- Happens when a cold air mass moves into a
warm air mass.
A.) The cold air forces the warm air to rise quickly.
B.) Makes the air rise twice as fast as warm fronts.
C.) This rapid movement can cuse large rain clouds if
the air is wet. .
D.) Large cumulus and nimbostratus clouds are
common.
E.) On a weather map they look like this:.
Cold Air
Warm Air
3. Occluded Front- Happen when two cold air masses collide and
force a warm air mass between them to rise.
A.) Very heavy rain will occur if the air mass is wet
enough.
B.) Cumulonimbus clouds and high winds are
common.
C.) This is the severe weather front.
D.) If air is dry high winds and moderate rain clouds
are still common.
E.) On a weather map they look like this:
Happens when pressure differences cause a
4. Stationary Front- warm front and a cold front to stop moving
towards each other.
A.) This type of front may stay in the same area for
days.
B.) If the air is wet, light precipitation and wind can
last for as long as the front is stationary.
C.) Nimbostratus clouds are common.
D. ) If the air is dry light winds and stratus clouds are
common.
E.) On a weather map they look like this:
Warm Air
Cold Air