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Warm Up
Copy Diagram, questions, and write answer
1.
2.
3.
When you hear “severe
storms” what do you
think of?
On average, how much
of the sun’s radiation is
reflected back into
space?
On average, how much
of the sun’s radiation is
absorbed by the
atmosphere and
clouds?
Weather Patterns and
Severe Storms
2.5.2B EXPLAIN HOW INTERACTIONS OF AIR
MASSES FORM FRONTAL BOUNDARIES,
CLOUDS, AND AFFECT WIND PATTERNS.
2.5.3A EXPLAIN FACTORS THAT AFFECT AIR
DENSITY AND UNDERSTAND THEIR
INFLUENCE ON WINDS, AIR MASSES,
FRONTS AND STORM SYSTEMS.
Before we begin…
 Watch as we draw the isotherms on the map.
 Remember, ISO means the “same”
Objectives
 Today I will be able to:
Describe
the factors that
characterize air masses
Analyze the development of fronts
when air masses meet
Relate severe weather to the
interaction of air masses
Key Points
 Air masses are characterized by their
temperature and moisture
 Air masses take on the characteristics
of the land/water they pass over
 When air masses meet a front is
formed and warm air is always forced
upward
 Warm fronts bring longer lasting,
gentle precipitation
 Cold fronts bring heavy, but short lived
precipitation
Air Masses and Weather
 Weather patterns result from the movement of large
bodies of air called air masses
 Air masses are characterized by similar
temperatures and amounts of moisture at
certain altitudes.
 When air masses move, the characteristics of the air
mass change and the weather in the areas over which
they move changes
Starts off at 460C
Ends up at
700C
Air Masses and Weather
Example of air mass/weather interaction:
 A cold, dry air mass moves over warm, tropical waters
 The air mass becomes warmer and wetter
 The weather over those waters becomes colder and drier

You try…
 A warm, dry air mass moves over a cold, wet area
 The air mass becomes ______________ and
_______
 The weather over that area becomes ____________
and ____________
When air masses meet… Fronts
 When two air masses meet, they form a front- the boundary
that separates the two
 There are 4 types of fronts
 Warm fronts
 Cold fronts
 Stationary fronts
 Occluded fronts
Fronts
 Warm fronts
 Form
when warm air moves into an area
formerly covered by cold air
 Shown on a weather map by a red line
with semi-circles pointing toward the
colder air
Warmer air
Colder air
Fronts
 Warm front
Fronts
 Warm fronts
 As
the warmer, less dense air
rises, it cools
This produces clouds and frequent
precipitation
Warm fronts move slowly, so the
precipitation is light-to-moderate
over a large area for a long period of
time
Fronts
 Cold fronts
 Form
when cold, dense air moves
into an area formerly occupied by
warmer air
 Shown on a weather map by a blue
line with triangles pointing toward
the warmer air
Colder air
Warmer air
Fronts
 Cold Front
Fronts
 Cold Fronts
 Move
much more quickly than warm
fronts
 Associated with heavy precipitation that
is short-lived
Fronts
 Stationary Fronts
 Form
when the flow of air is neither
toward the cold air mass, nor toward
the warm air mass
 The front does not move
 Shown by blue triangles on one side
and red semicircles on the other
 Gentle
to moderate precipitation
Fronts
 Occluded Front
 Forms
when a cold front overtakes a
warm front
 Complex weather patterns
Finish worksheet, then answer questions
1. A cold, dry air mass that moves over warm,
tropical waters will likely become ____and
_______.
2. Along which type of front is the intensity of
precipitation generally heavy, but short-lived?
3. Along a front, which type of air is always forced
upwards?
Severe Storms
 Thunderstorms
 Develop
when warm, humid air rises
in an unstable environment
Warm air
Heavy rain
Cooler air
Severe Storms
 Tornadoes
 Violent
windstorms
 Form as a vortex extends down from a
cumulonimbus cloud
A vortex is a rotating column of air
Most
tornadoes form along with severe
thunderstorms
Severe Storms
 Tornadoes
 Tornado
Watches: there is the possibility
of a tornado in the area
 Tornado Warning: a tornado has been
spotted in the area or is indicated by
radar
Damage Caused by Tornadoes
 Extremely high winds can tear buildings apart, slip
cars, and even suck the water out of a riverbed
Severe Storms
 Hurricanes
A
hurricane is a large, rotating tropical
weather system with wind speeds of at
least 74 mph
 Hurricanes are the most powerful
storms on Earth
 In other countries they are also known
as typhoons and cyclones
 http://www.wral.com/weather/hurric
anes/story/3311088/
 http://www.wral.com/weather/hurric
anes/video/9924105/
How Do Hurricanes Form?
 A hurricane begins
as a group of
thunderstorms
moving over tropical
ocean waters
 Winds traveling in
two different
directions collide
causing the storm to
spin
 Warm water gives
the storm energy and
causes it to grow
Structure of a Hurricane
The eye is a zone of scattered
clouds and calm averaging
about 20 kilometers in
diameter at the center of a
hurricane. The eye has the
warmest temperatures.
The eye wall is a doughnut-shaped
area of intense cumulonimbus
development and very strong winds
that surrounds the eye of a hurricane.
Damage Caused by Hurricanes
 Hurricane winds can
knock down trees and
telephone poles
 However, the most
damage during a
hurricane comes from
flooding due to heavy
rain and storm surges
 A storm surge is a wall
of water that builds up
over the ocean and can
be up to 20 feet before
it crashes onto the
shore
WARM UP
5/11/10
 The boundary that separates different air masses is




called _____
What is the most abundant gas in the atmosphere?
What is the most important gas for understanding
atmospheric processes?
Air that has reached its water vapor capacity is
____________.
What type of winds are produced by steep pressure
gradients?
FRONT ACTIVITY
 You will be completing this activity in groups
 For each of the pressure systems and
fronts:
 Draw the symbol
 Explain the effect these have on weather
YOU BE THE METEOROLOGIST
 TODAY-Lots of clouds, a stiff northeast wind, and
periods of rain will make for a chilly and wet day. Highs
will struggle to reach the upper 50s here in the Triangle,
but low 60s are very possible south and east of Raleigh.
 SATURDAY-Happy Halloween! No spooky weather is
expected at this time. Expect mostly sunny to partly
cloudy skies and slightly milder temperatures with highs
in the mid to upper 60s. The evening looks nice for trick
or treaters, and remember that later tonight we "fall
back" to standard time.
YOU BE THE METEOROLOGIST
 Pretend that you are a meteorologist for Apex, NC.
Write a script for you to read during the news
describing the fronts and weather patterns Apex has
experienced over the past 7 days. Your script should be
at least 7 sentences long and be accurate.
 EXAMPLE:
 On Sunday, Apex experienced a High pressure
system causing the weather to be clear and
sunny, with highs in the upper 80’s.
 Note: exact temperatures may be made up.
as you watch, write at least 5 pieces of info
for each of the following categories. Your
paper should look like this
 HOW HURRICANES
FORM
1.
2.
3.
4.
5.
 TOOLS AND
TECHNIQUES FOR
PREDICTING
HURRICANES
1.
2.
3.
4.
5.
EXIT TICKET
 What type of front is drawn as a line with
semi-circles extending out?
 True or false?- In a cold front the symbols
on the front line point toward the cold air.
 What type of front is associated with heavy,
short-lived precipitation?
 High pressure systems are associated with
what weather conditions?