8.10 B Weather Maps
Weather Map Interpretation
Formative
Name ___________________________________
Weather is all the conditions of the atmosphere, such as temperature, humidity, precipitation,
wind and cloud cover. The uneven heating of Earth's surface by the sun causes weather.
The interaction of the oceans and atmosphere, including solar radiation helps us understand
how weather forms and sustains itself.
Describing the weather and how it changes is recorded on weather maps. Information on
temperature, pressure, wind, radiation, and condensation helps meteorologists to predict
future weather patterns.
Things to look for on a weather map:
Precipitation refers to the way water is precipitating. Fog is low clouds. Snow is crystallized water. Rain is liquid water.
Thunderstorms can refer to severe rain, including hail. Drizzle refers to light rain, while showers are a steady downpour of rain.
Wind speed and direction shows the direction of where the wind in coming from. The direction can be determined by
comparing the line to north. So if the direction is south to north, you would refer to the wind as coming from the south. The
speed of the wind is measured in knots which is a nautical term that is measured as 1.852 km per hour.
Atmospheric Pressure. The pressure is the weight of the vertical column upon an area. A barometer measures
atmospheric pressure. Areas of high pressure indicate clear weather conditions while areas of low pressure indicate
possibilities of unstable weather conditions.
Fronts and pressure systems refer to centers of high or low pressure system. The different fronts include a cold front, warm
front, stationary front, and occluded front. A front is a line or boundary between two different air masses. The air masses clash
along the front so weather along a front is stormy.
Different kinds of fronts are produced depending on how the air masses come together.
1. Cold Front. When a cold air mass pushes into and under a warm air mass.
§ Heavy downpours, gusty winds, and cooler temperatures
§ On hot summer days - causes thunderstorms, followed by lower temperature and humidity
2. Warm Front. When a warm air mass pushes into and over a cold air mass. The warm air slides up and over the cooler
air. Warm fronts move slower than cold fronts,
§ Light precipitation lasting a day or two and warmer temperatures.
§ When the sky is overcast all day with light rain
3. Stationary Front. When two air masses meet and stay in the same position for a long time. Very slow moving.
§ Light precipitation, overcast for a few days with light rain
4. Occluded Front. Three fronts come together. It forms in stages. It begins with a stationary front between a cold and a
warm air mass. Then a cold front comes through faster and lifts up the warm air.
§ Very heavy rains, severe weather (thunderstorms and strong winds)
Symbols and Direction of Movement
8.10 B Weather Maps
Weather Map Interpretation
Formative
Name ___________________________________
Air masses bring variety of weather
An air mass is a large body of air that has similar temperature and moisture properties throughout.
Once an air mass moves out of its source region, it changes as it encounters surface conditions
different than those found in the source region. For example, as a polar air mass moves southward, it
encounters warmer land masses and consequently, is heated by the ground below. Air masses typically
clash in the middle latitudes, producing some very interesting weather.
Five basic types of air masses determine the USA's weather. They can bring anything from scorching
heat to bone-chilling cold depending on the type of air mass. The USA's most violent weather usually
occurs in spring when continental polar air clashes with maritime tropical air.
These air masses are:
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Continental Arctic (cA): Extremely cold temperatures and very little moisture. These usually
originate north of the Arctic Circle, where days of 24 hour darkness allow the air to cool to
sometimes record-breaking low temperatures. Such air masses often plunge south across
Canada and the USA during winter, but very rarely form during the summer because the sun
warms the Arctic.
Continental polar (cP): Cold and dry, but not as cold as Arctic air masses. These usually form
farther to the south and often dominate the weather picture across the USA during winter.
Continental polar masses do form during the summer, but usually influence only the northern
USA. These air masses are the ones responsible for bringing clear and pleasant weather
during the summer to the North.
Maritime polar (mP): Cool and moist. They usually bring cloudy, damp weather to the USA.
Maritime polar air masses form over the northern Atlantic and the northern Pacific oceans.
They most often influence the Pacific Northwest and the Northeast. Maritime polar air masses
can form any time of the year and are usually not as cold as continental polar air masses.
Maritime tropical (mT): Warm temperatures with copious moisture. Maritime tropical air
masses are most common across the eastern USA and originate over the warm waters of the
southern Atlantic Ocean and the Gulf of Mexico. These air masses can form year round, but
they are most prevalent across the USA during summer. Maritime tropical air masses are
responsible for the hot, humid days of summer across the South and the East.
Continental Tropical (cT): Hot and very dry. They usually form over the Desert Southwest and
northern Mexico during summer. They can bring record heat to the Plains and the Mississippi
Valley during summer, but they usually do not make it to the East and the Southeast. As they
move eastward, moisture evaporates into the air, making the air mass more like a maritime
tropical air mass. Continental tropical air masses very rarely form during winter, but they usually
keep the Desert Southwest scorching above 100 degrees Fahrenheit during summer.
8.10 B Weather Maps
Weather Map Interpretation
Formative
Name ___________________________________
8.10 B Weather Maps
Weather Map Interpretation
Formative
Name ___________________________________
8.10 B Weather Maps
Weather Map Interpretation
Formative
Name ___________________________________
Use the weather information page and weather map to complete the table below. Draw the
symbols and locate on the map where each is occurring.
Symbol Name
Draw Symbol
Where do you see it on the
weather map?
Rain
Snow
Wind Direction
Overcast
Clear Skies
Partly Cloudy
High Pressure
Low Pressure
Temperature
Warm Front
Cold Front
Occluded Front
Stationary Front
What general direction do Warm fronts come from?________________ Cold front?_________________
How does the direction of the frontal passage impact the wind direction?__________________________
Areas receiving rain/snow all have something in common. Identify two things that are occurring in these
areas that are triggering this precipitation? __________________________________________________
Describe the type of cloud conditions (overcast, clear, or partly cloudy) found around areas of high
pressure. __________________________________ Low pressure_______________________________
8.10 B Weather Maps
Weather Map Interpretation
Formative
Name ___________________________________
Use the air masses information page to complete the table below
What type of air mass affects
Texas?
____________________________
____________________________
What is the weather like in
Canada?
____________________________
____________________________
Describe the weather in Northern
Alaska.
____________________________
____________________________