Transcript Highs, Lows, and Fronts

Highs, Lows, and Fronts
Highs, Lows, and Fronts
Name
Clouds before
Air that Rises
Front Arrives
Weather after
Front Passes
Time Required
to Pass
Warm Front
Cirrus,
Altostratus
Warm, Humid,
Cloudy
Long
Cold Front
Cumulonimbus Warmer
Dry, Cold,
Clear
Short
Warmer
Description of a Cold Front
What does the H on a weather map
represent?
It refers to a region of High Pressure.
Description of a Cold Front
What sort of weather will you find there?
Clear, sunny, cool, stable, mild winds.
Description of a Cold Front
One morning you wake up and the sky is
clear. By noon, clouds that started like jet
trails are making streaks across the sky.
By dinner time, the clouds have thickened
into a lower, grey, featureless blanket over
the sky.
What is happening in terms of fronts?
What do you think the weather will be like
that night and the following day?
Description of a Cold Front
A warm front is coming in, hence the
formation of cirrus clouds.
The thick, grey blanket are altostratus
clouds.
Description of a Cold Front
By night time, it is likely that nimbostratus
clouds will have formed and light rain will
begin to occur.
The light rain will continue into the next day
because warm fronts pass slowly.
Highs and Lows
Air moves from an area of
high pressure to an area
of low pressure.
As cool air descends, it
becomes more dense
and draws the air from
above.
This describes a high
pressure system.
Highs and Lows
At the base of a high
pressure system, air
is pushed out. Why?
To equalize pressure,
air has to move from
high pressure to low
pressure.
Highs and Lows
Because of the Coriolis
Effect, the air at the base
of a high pressure system
veers to the right in the
Northern Hemisphere.
As a result, high pressure
systems move in a
clockwise direction, called
an anticyclone.
Quick Questions
Why do high pressure systems cause clear
skies?
Cool air descending prevents cloud
formation b/c it is not a moist/humid as
warm, cloud forming air.
Cool air can’t hold very much moisture.
Quick Questions
Why do high pressure systems cause
weather to stay the same for days?
B/c they are large, usually the size of an
entire air mass, therefore they take a while
to move out of an area.
Cold Fronts
C
O
M
P
A
R
E
C
O
N
T
R
A
S
T
Warm Fronts
•Both are boundary lines between 2 different air masses.
•Both are formed when a warmer and a cooler air mass meet each other.
•Both leave the temperature of the air different then before they arrived.
•Both involve cloud formation and rain/snow.
•Both create rising air.
•Created when a cooler air mass
overtakes a warmer air mass.
•Warm air rises b/c it is pushed up
by the cool air and b/c it is less
dense.
•Steeply sloping curved line front.
•Heavy rain and wind.
•Passes through quickly.
•Cool, dry, and clear skies after
•Mainly cumulus type clouds
•Created when warmer air mass
overtakes a cooler air mass.
•Warm air rises just b/c it is less
dense.
•Gentle sloping straight lined front.
•Light rain and wind.
•Passes through slowly.
•Warm, humid, and cloudy after.
•Mainly stratus type clouds.