High and Low Pressure Systems Overview
Regents Earth Science
HIGH AND LOW PRESSURE
SYSTEMS
WEATHER SYSTEMS UNIT
By the end of this class, you will be able to:
*Compare and contrast high and low pressure
systems
*Identify areas of high and low pressure on a
weather map
DO NOW: What’s in a letter?
Take a moment to think about what each
letter stands for when used on a weather map
Compare/Contrast Chart
High and Low Pressure
High Pressure
LOW PRESSURE
Low vs. High
Identify one center of high pressure and one center of low
pressure using the letters on the map below. Be able to briefly
explain your answer.
FRONTS
Front: The leading edge of an air
mass-branch from low pressure
systems
Fronts are shown by
lines with symbols that
show the type of front
and the direction of
movement
Fronts-
Warm front: an area
where a warm air mass
is replacing a cooler air
mass
What to Expect
Before the front passes: cool or
cold temperatures, a falling
barometer, an increase and
thickening in clouds, light-to-
moderate precipitation, winds
from the south-southeast, rise
in dewpoint
After the front has passed:
Warmer and more humid
weather conditions, clearing
clouds, a brief rise in
pressure, winds from the
south-southwest, high
dewpoint
NOTE: “A high dewpoint” means that the
temperature and dewpoint are close
together. (ex. 32F temp, 30 F dewpoint)
“A low dewpoint” means that the
temperature and dewpoint are far apart (ex.
55F temp, 30F dewpoint)
There is ALWAYS a dewpoint!
Cold Front
Cold front: an area where
a cold air mass is
replacing a warmer air
mass
What to Expect
Before the Front: winds from
the south-southwest, warm
temperatures, a falling
barometer (dropping pressure),
an increase in clouds, a short
period of precipitation and a
high dew point
After the Front: winds
from the west-northwest,
a drop in temps, a rise in
pressure, showers
followed by clearing skies,
and a falling dewpoint
Stationary Front
Stationary Fronts: a
boundary between air masses
that are not moving
What to expect: a
noticeable change in wind
direction or temperature
when crossing from one
side of the front to the
other
Occluded Fronts
Occluded Front: occur
when warm air is pushed
above Earth’s surface by
cooler air that is closing in
from both sides
A developing cyclone usually has a
warm front and a faster moving cold
front that wraps around the storm.
An occluded front forms when cold air
behind the cold front catches up to the
warm front, which is stuck behind the
cool air already in place
What to expect: A change in temp.,
dewpoint or wind direction is possible
Occluded Front Development
Phase 1:
Phase 2
Animation of Fronts <3
Animation of Fronts
Movement of Weather Revisited
Most of the tracks (paths)
follow a southwest to
northeast pattern because of
the United States’ location in
the prevailing southwest
wind belt
Video:
Tying it Together!: Jet Streams, Pressure
Systems and Fronts
The characteristics and differences between high and low pressure systems, learn how to identify them on weather maps, and understand the impact they have on weather patterns. Discover the factors that determine pressure systems and the associated weather conditions.
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Presentation Transcript
HIGH AND LOW PRESSURE SYSTEMS Regents Earth Science WEATHER SYSTEMS UNIT By the end of this class, you will be able to: *Compare and contrast high and low pressure systems *Identify areas of high and low pressure on a weather map
DO NOW: Whats in a letter? Take a moment to think about what each letter stands for when used on a weather map
Compare/Contrast Chart High and Low Pressure High Pressure Low Pressure Type of phenomenon Determined by Moving inward on isobars Density of air Representation on a map Motion of air Weather system Changes in air pressure Pressure Increases Pressure Decreases Higher (increases) H (typically blue) Clockwise, air sinks Lower (decreases) L (typically red) Counterclockwise, air rises Cyclone Convergence Also known as Motion of air causes a zone of Stability of atmosphere Typical weather Anticyclone Divergence Stable Clear sky Dry Unstable Stormy
Low vs. High http://ts3.mm.bing.net/images/thumbnail.aspx?q=1504704345930id=17071fb0125d236b9ab58be6e5d058f0
Identify one center of high pressure and one center of low pressure using the letters on the map below. Be able to briefly explain your answer.
FRONTS Front: The leading edge of an air mass-branch from low pressure systems
Fronts are shown by lines with symbols that show the type of front and the direction of movement
Fronts- Warm front: an area where a warm air mass is replacing a cooler air mass Go to fullsize image
What to Expect Before the front passes: cool or cold temperatures, a falling barometer, an increase and thickening in clouds, light-to- moderate precipitation, winds from the south-southeast, rise in dewpoint
After the front has passed: Warmer and more humid weather conditions, clearing clouds, a brief rise in pressure, winds from the south-southwest, high dewpoint
NOTE: A high dewpoint means that the temperature and dewpoint are close together. (ex. 32F temp, 30 F dewpoint) A low dewpoint means that the temperature and dewpoint are far apart (ex. 55F temp, 30F dewpoint) There is ALWAYS a dewpoint!
Cold Front Cold front: an area where a cold air mass is replacing a warmer air mass Go to fullsize image
What to Expect Before the Front: winds from the south-southwest, warm temperatures, a falling barometer (dropping pressure), an increase in clouds, a short period of precipitation and a high dew point
After the Front: winds from the west-northwest, a drop in temps, a rise in pressure, showers followed by clearing skies, and a falling dewpoint
Go to fullsize image Stationary Front Stationary Fronts: a boundary between air masses that are not moving
What to expect: a noticeable change in wind direction or temperature when crossing from one side of the front to the other
Occluded Fronts Occluded Front: occur when warm air is pushed above Earth s surface by cooler air that is closing in from both sides Go to fullsize image
A developing cyclone usually has a warm front and a faster moving cold front that wraps around the storm. An occluded front forms when cold air behind the cold front catches up to the warm front, which is stuck behind the cool air already in place What to expect: A change in temp., dewpoint or wind direction is possible
Occluded Front Development Phase 1: Phase 2
Animation of Fronts <3 Animation of Fronts
Movement of Weather Revisited Most of the tracks (paths) follow a southwest to northeast pattern because of the United States location in the prevailing southwest wind belt Video: Tying it Together!: Jet Streams, Pressure Systems and Fronts
