Weather Patterns Notes

© Kesler Science, LLC

Vers. 8/20

Weather
Maps

Presented by Kesler Science

© Kesler Science, LLC

Weather Maps

Essential Questions:

Reflect on the Essential
Questions before you dive in…

1. If you were quizzed today,
which questions would you know
the answers to already?

2. Which questions would you
need to learn more about to
answer confidently?

1.

How can you use
weather maps to
explain global weather
patterns and their
influence on local
weather?

2.

How can you interpret
high and low pressure
areas as well as fronts
on a weather map?

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Weather Maps

Gravity

14.7 lbs

1 sq. in.

column of air

• Pressure caused by the weight of air above an

area

• Pressure decreases with increasing height

above Earth

• A 1 square inch column of air measured from

sea level to the top of the atmosphere weighs
approximately 14.7 pounds

Atmospheric (Air) Pressure

Sea Level

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Weather Maps

Mercury Barometer

• Measured with a barometer in millibars

• Average barometric pressure at sea level is

1013.25 millibars or 29.92 Hg (inches of
mercury)

• High pressure –creates greater pressure on the

barometer

• Low pressure - creates less pressure on the

barometer

Air Pressure

What causes air pressure?

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Weather Maps

High Pressure H

As air cools, it becomes more dense and sinks
toward the Earth’s surface spinning clockwise.

Low pressure L

As air warms, it becomes less dense and rises
above the Earth’s surface spinning
counterclockwise.

Atmospheric (Air) Pressure

What do you notice about the colors
of the high pressure and low
pressure symbols? Why do you think
they are colored this way?

Open Ended

When flying in airplanes, the altitude causes the outside air pressure to be too low for
humans to withstand. Before the air is filtered into the passenger cabin there are many
processes that must happen, including cooling the air. Why aren’t we able to open airplane
windows?

Open Ended

Describe the relationships between changes in heat, density, and air pressure.

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Weather Maps

Describe the weather that would
occur if a high pressure system
moved into your area ?

H

L

High Pressure
•

Sunny, clear skies

•

Calm winds, spiral clockwise

•

Cool, dry air

•

Higher than normal - 30.5 Hg

Low pressure
•

Cloudy, stormy skies

•

Strong winds, spiral counterclockwise

•

Warm, moist air

•

Lower than normal - 28.9Hg

Atmospheric (Air) Pressure

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Weather Maps

• A line connecting points of equal atmospheric

pressure

• Measured in millibars - mb

• One millibars is equal to about .02953 inches

of mercury

Isobars

What are isobars?

Think About It

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Topographic maps use contour
lines to show the elevation
(height) of the surface of Earth.
The closer the contour lines are,
the steeper the elevation. A
contour line represents an area
that has the same elevation.

Weather map with isobars.

There are some obvious visual similarities between isobars and contour lines. Compare

and contrast weather maps with isobars and topographic maps with contour lines.

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Weather Maps

Tornados

850 mb, 25.17 Hg

Possibly lowest ever recorded

Hurricanes

882 mb, 26.05 Hg

Lowest U.S. storm measured

Low Pressure in Storms

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Weather Maps

•

A large body of air that has relatively uniform
temperature and humidity

•

Air masses can originate

•

over land (Continental)

•

over water (Maritime)

•

Cold air masses tend to approach from N, NW
or W

•

Warm air masses tend to approach from S, SE
or E

Air Masses

What is an air mass and how

can you tell them apart?

Match

Match the following

• Warm, Wet

• Warm, Dry

• Cold, Wet

• Cold, Dry

Martime Tropical

Continental Tropical

Maritime Polar

Continental Polar

• Martime Tropical

• Continental Tropical

• Maritime Polar

• Continental Polar

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Weather Maps

• Cooler air masses (H) are more dense and flows

toward areas that are less dense, warm, and
moist (L)

• High pressure areas move into low pressure

areas

Frontal Movement

Study the graphic above. Describe
the movement of wind.

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Weather Maps

Cold

Warm

Stationary

Occluded

•

The boundary between two air masses

•

Classified by which type of air mass (cold or
warm) is replacing the other

•

Map symbols point in direction front is moving

Front

What direction do the arrows on the
cold front point to?

Match

Match the following

Cold Front

Warm Front

Stationary Front

Occluded Front

• Cold Front

• Warm Front

• Stationary Front

• Occluded Front

Multiple Choice

What direction is the warm front in Colorado moving?

• North

• East

• West

• South

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Weather Maps

•

A cold air mass is replacing a warm air mass

•

Air behind the front is colder and drier

•

Pressure increases (H)

•

Moist air is pushed up over the cold air

•

Showers and thunderstorms form along
leading edge of front

Cold Front

Describe the weather as a cold front
approaches.

Describe the weather after the
passage of the front.

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Weather Maps

• A warm air mass is replacing a cold air mass

• Air behind the front is warm and moist

• Pressure goes down (L)

• Slow moving, gradual rise of warm air over

cold air

• Widespread, continuous precipitation occurs

along and ahead of the front

Warm Front

Describe the weather as a warm
front approaches.

Describe the weather after the
passage of the front.

Multiple Choice

Which type of front is more likely to have strong thunderstorms?

• Cold Front

• Warm Front

Multiple Choice

What type of front is pictured?

• Cold Front

• Warm Front

Multiple Choice

What type of front is pictured?

• Cold Front

• Warm Front

Think About It

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The local weather person in Seattle reports cool, moist
air masses moving in. What type of air mass would this
be? What type of weather might accompany it?

Seattle, Washington

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Weather Maps

• A boundary between two different air masses,

neither of which is strong enough to replace the
other

• Light rain over several days

Stationary Front

What does the word stationary
mean?

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Weather Maps

•

Two cold air masses converge on a warm air
mass

•

Occurs when a fast moving cold front
overtakes a warm front pushing it up and over
cold air

•

Thundershowers form along the front

•

After frontal passage the sky is usually clear
and dry

Occluded Front

What happens to air masses on

occluded fronts?

Match

Match the following

occluded front

stationary front

cold front

• occluded front

• stationary front

• cold front

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A

•

Barometer (A) – measures atmospheric pressure in mb & Hg

•

Anemometer (B) - measures wind speed in mph

•

Thermometer (C) - measures temperature in oC & oF

Weather Instruments

B

C

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Weather Maps

•

Weather Balloon (A) - carry instruments to
high altitudes to measure pressure,
temperature, humidity, and wind speed

•

Compass Rose (B) - helps determine wind
direction when reading weather maps

•

Wind Vane (C) - measures wind direction as
N,S,E,W

Weather Instruments

A

B

C

Match

Match the following

• Anemometer

• Barometer

• Thermometer

• Wind Vane

wind speed

air pressure

air temperature

wind direction

• wind speed

• air pressure

• air temperature

• wind direction

Give your best answer to...

1.

Describe the movement of air/wind. (What direction does
it move?)

2.

Describe how to use a weather map showing high and low
pressure and fronts to explain how air movement affects
local weather.
Check for

Understanding