Name __________________________
Date _____________
Chapter 3 Notes: Air Masses and Fronts
**What causes wind? All winds are caused due to __differences__ in air pressure.
Winds blow from high to low: H  L
1. ___Weather____ describes the conditions of the atmosphere at a given location for a
short period of time.
2. ____Climate____ is the characteristic weather that prevails from season to season
and year to year.
3. The _unequal___ _____heating___ of Earth’s surface is the cause of weather.
4. Air masses form when air remains ___stationary (stagnant, still)__ over a large
section of Earth’s surface and takes on the conditions of ____temperature____ and
___moisture (humidity)______ from that location.
5. Weather conditions at a location are determined primarily by the ___temperature___,
____moisture____, and ___pressure____ of air masses over that location.
6. Most local weather condition changes are caused by movement of _air_ _masses_.
**7. _FRONTS____ are boundaries between air masses. ___Precipitation____ is likely
to occur at these boundaries.
**8. High-pressure systems (highs, H) generally bring __CLEAR____ weather. Lowpressure systems (lows, L) usually bring _cloudy__, ____wet (stormy)___ conditions.
**9. The general movement of highs and lows in the United States is from _WEST_ to
_EAST_.
**10. Air mass – huge body of air with similar __temperature__, ___moisture
(humidity)___, and _______pressure__.
11. Air masses are classified based on their __temperature__ and _moisture/ humidity_
a. Tropical - _Warm_, forms over a __warm (near equator)___ area;
b. Polar - ___Cold___, forms over a __cold (near a pole)_ area;
c. Maritime - __Wet_, forms over an ___ ocean______;
d. Continental - _Dry__, forms over a __continent (land)_____.
12. Four main types of air masses affect the United States
a. Maritime Tropical (mT) – form over _warm_ ___ocean__, are
__warm__ and ___moist/wet/humid_____.
b. Maritime Polar (mP) – form over ___cold___ ____ocean_, are
___cold___ and ___ moist/wet/humid ___.
c. Continental Tropical (cT) – form over _warm____ ___land___, are
____warm____ and ____dry_______.
d. Continental Polar (cP) – form over ___cold__ ___land__, are
____cold____ and ___dry______.
13. What moves air masses across the U.S.? __jet stream___ ___ (prevailing winds) _
**14. When two different air masses meet you get a __front__, and often storms.
15. Recall: __cold__ air is dense and sinks; __warm____ air is less dense and rises.
16. There are four types of fronts: cold front, warm front, stationary front, occluded front
a. Cold Front – forms when _cold__ air catches up to ___warm__ air
forcing the warm air upward. (Cold front = the front of a cold air mass)
This causes ___clouds, thunderstorms__ and brings ___cold__ air into
the area; cold fronts move __quickly_____.
b. Warm Front – forms when _warm_ air catches up to ___cold___
air, and the warm air slowly __rises_. (Warm front = the front of a warm air mass)
This causes a few days of __clouds and rain_____ and brings
___warm__ air into the area; warm fronts move ___slowly_______.
c. Stationary Front – forms when __cold__ and ____warm_ air meet,
but neither pushes the other, so the front stalls. (stays still)
This causes many days of ___clouds and rain______,
until one air mass starts moving again.
d. Occluded Front – forms when a cold
front catches up to a warm front (and tries
to pass!), causing __warm___ air to get
caught between two __cold___ air
masses. Warm air in the center rises, this
causes __severe thunderstorms___.
High and Low Pressure Systems
**Winds blow from high to low*
17. Cyclones – Low pressure systems – Lows – L
Winds blow counterclockwise, inward,
and then upward
Brings clouds,
rain, storms
18. Anticyclones – High pressure systems – Highs – H
Winds blow clockwise, downward, and outward
Brings clear skies, NO precipitation,
(could be warm or cold)
19. Which city, A or B, is more likely to be receiving precipitation? Explain.
City A is probably experiencing
precipitation since City A is near
a (stationary) front.
City B is probably NOT
experiencing precipitation since
City B is near a High pressure
center / is NOT near a front
Severe Weather Safety
1. Safety in severe weather
*What is a storm? A __temporary___ disturbance in the atmosphere.
a. Thunderstorms – thunder, lightning, heavy rain, wind
Safety – get in a car or a sturdy building; AVOID trees!!!
AVOID being the tallest object in an area, AVOID being near the
tallest object in an area; AVOID metal/electronics/water/pool/ocean
b. Winter storms – snow, blizzard (heavy snow and wind), sleet, freezing rain
Safety – stock up on gasoline, food, water, batteries, flashlights,
blankets, warm clothes, snow shovel, and rock salt or other ice-melter
c. Heat Wave – wear light colored, loose fitting clothing, wear sunscreen, keep
cool in air conditioning whenever possible, and drink lots of fluids
d. Hurricane Safety – ___EVACUATE____ if advised, board up windows,
listen for updates, watch out for flooding and high winds, prepare for blackouts,
stock up on food and water. Also bring loose objects inside, or tie them down.
e. Tornado Safety – If there is a tornado warning (means a tornado is in your
area) or you see a tornado, go to a ___BASEMENT__ and listen to radio or
TV for updates. If there is no basement, move to the center of the lowest
level, away from windows. Sitting in a bathtub or closet with a mattress,
blankets, or pillows protecting you from debris could also save your life.
f. Lightening Safety – get in a car or building, if caught in an open area get
LOW, stay away from _metal___, water, and tall objects.
Weather Forecasting
A. Typical Storm Tracks across the US go from __WEST___ to ___EAST__
because of the __jet stream / prevailing westerlies___
B. Based on typical storm tracks across the US, in which direction will this
frontal system most likely travel?____toward the east or northeast______
1. Predict upcoming changes in
temperature and precipitation
for cities A and B. Explain your
answer. City A will soon be
warmer, and should get rain since a
warm front is approaching
2. Compare the temperatures in
city B and city C. Explain your
answer. City C should be colder,
since the cold front already passed
through it, but City B is still behind a
warm front / is in a warm air mass
Typical Tracks of Hurricanes impacting the US are from __the Southern Atlantic
Ocean__, and travel toward _Florida/the east coast/the gulf coast__ because of __the
prevailing (easterly) winds__
C. Review of Hurricane Safety:
a. What are some dangers that hurricanes pose?
Strong winds, heavy rains, storm surges, and flooding
b. What should you do if a hurricane is predicted for your area?
Stock up on food, water, gasoline, batteries, and flashlights
Bring all loose objects inside, or tie them down
Board up your windows
Evacuate if recommended to do so