Download Chapter 20 – Weather

Chapter 20 – Weather
I.
Air Masses and Weather
 __________________– the study of processes
that govern Earth’s Atmosphere
A. Origin of an Air Mass
1. An Air Mass is a large body of air with the same
_____________and _____________
2. The humidity and temperature of the air mass is
determined by where they _______________
i.
Over a southern ocean – moist and warm
3. When the air mass travels, it takes with it the
temperature and humidity of its place of____________.
B. Origins of air masses
1. Classification due to where they form
a. Continental Arctic (cA) – extremely _______and ___
 Forms over land (continental) and cold
temperature causes it to be ________.
b. Continental Polar (cP) – _________ and _______
c. Maritime Polar (mP) maritime – moist; plus ______
and _____________
d. Maritime Tropical (mT) – _________and _______
e. Continental Tropical (cT) – ________ and _______
II.
Fronts and Lows
A. What is a front?
1. Front – Boundary that separates opposing air
__________
a. Can range from 200 meters, to _______ kilometers
b. Can be as high as ________ kilometers
c. Can be as long as ________________ kilometers
2. Air masses on either side differ in ____________,
temperature and ______________ direction.
B. Kinds of fronts
1. Cold front – boundary between an advancing ______air
mass and _______________ air mass it is displacing.
a. Cold air denser therefore it slides __________the warm
air in front of it, forming a __________ slope
b. The precipitation along the cold front is usually heavy
and fast (__________________)
c. However, the passing front may cause no greater
change than a shift in__________ _______________.
2. Warm front – boundary between an advancing ________
air mass displacing a ________________ air mass
a. Warm air is less dense therefore, it _________ up over
the cold air forming a _____________ slope.
b. The first signs of an approaching _________ front
are high ___________ clouds, which are followed by
cirrostratus then lower _______________ clouds.
c. Eventually nimbostratus clouds which give ______ rain
or snow.
3. _______________ front – occurs when the faster
moving cold front catches up to a __________ front.
a. The _________ air gets pushed up between the two
cold air masses causing cloudiness and ____________.
4. ________________ front – front is not moving forward
a. May give many days of steady rain
causing_______________.
C. Life Cycle of a Mid-Latitude Low
1. _______air mass meets a _________ air mass in the mid
latitudes
2. Circulation begins due to the warm air moving
_______and the ____________southward (p. 442)
3. The circulation around the Low is __________________
in the Northern Hemisphere
4. This counterclockwise motion of a Low ________ air
off the earth’s surface. Air is constantly spiraling into
a ______________________________ system.
5. Throughs and Highs (p. 443)
6. __________ pressure is associated with
_______________ weather.
7. _____________ pressure is associated with
_____________ conditions.
III. Thunderstorms and Tornadoes
A. Thunderstorms – storms with lightning and thunder formed
in __________________________ clouds.
1. The cloud can be as tall as ___________
2. Formed in convection cells – warm air being lifted ___
while cool air __________ (p. 445)
3. Often form along _______ there may be many ______
4. ____________ line – many thunderstorms along a ______
5. Supercells – very large singlecell thunderstorm that can
produce ______________
6. Lightning – discharge of ___________ – cloud to cloud,
cloud to ground. Can occur in thunderstorms,
snowstorms, dust storms or volcanic eruptions.
B. _______________ – byproducts of supercell thunderstorms
1. Violently rotating column of air
2. Tornado formation
3. Form from between the wall clouds of a_____________
(p. 447)
4. A tornado’s funnel cloud results when the air pressure
at its center is very _________and air sucked into the
funnel expands and cools; water vapor in the air
condenses.
C. Storm and Tornado watches and warnings
1. _____________ – conditions are right
2. _______________ – one has been spotted
IV. Hurricanes and Winterstorms
A. _______________ – huge rotating storm of tropical origin
that has sustained winds of at least 119 km/h
1. Winds and rain are strongest at the ________wall
2. Hurricanes rely on the transfer of ________ from the
____________, they form only when surface ocean
waters are sufficiently warm, and they weaken as soon
as they make landfall.
3. ___________________ by global wind patterns
4. Storm ____________ results, in part, from strong winds of
the eye wall which blows water into a
________________.
5. If storm surge strikes land the same time as high tide,
hurricane disaster ______________.
6. Hurricanes are ranked according to the _________Simpson Hurricane Scale on p. 452
B. Winter Storms
1. Blizzard – must have winds higher than _______ ,
temperature ___________ or lower, and reduced
visibility due to falling or blowing snow
V.
Forecasting Weather
A. Gathering data
1. ____________________ – visible images and infrared
a. Visible – the whiter the clouds the thicker –
meteorologists can track the clouds to get _________
and ________________.
b. Are not available at ____________
c. Infrared satellite – use temperature to plot ________
d. The cooler the cloud _________ the higher it is in the
atmosphere
e. Can be used at night
2. ____________________ – measure temperature,
pressure and humidity of air at different altitude.
a. Attached to a large balloon and tracked by _______
b. Identifies the shape of the __________ stream
3. Surface Observations
a. Most are at _____________
b. Information can help to locate __________, highs and
lows
c. Provide – temperature, ________ point, barometric
pressure, wind speed and direction, visibility,
precipitation, height of clouds and the amount.