Transcript Unit 3 Powerpoint

Wednesday, November 16th
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Attendance
Go over Unit Test 3
Make-up work
and/or weather dvd
Unit 11
Weather Forecasting
I. Weather Maps
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A. Synoptic forecasting is based on
looking at a summary of the total
weather picture at a particular time.
– A synoptic weather map is made by
measuring atmospheric weather variables
at thousands of weather stations around
the world.
I. Weather Maps
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B. Field – a region of space that has a
measurable quantity at every point.
– Elevation is measured by contour lines on a
topographic map.
– Temperature is measured by isotherms on a
weather map.
– Atmospheric pressure is measured by isobars
on a weather map.
– Isolines are “generic” lines that connect equal
values.
I. Weather Maps
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C. Air masses are large regions of air with fairly
uniform characteristics like temperature,
humidity, winds and air pressure.
– Identified by the temperature and moisture content.
– The code has two letters.
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The first letter is lower case and represents moisture.
– m = maritime = moist
– c = continental = dry
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The second letter is upper case and represents temperature.
– T = tropical = warm
– P = Polar = cool
– A = Arctic = frigid (very cold)
I. Weather Maps
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C. Air Masses
– The boundaries between air masses are
called frontal boundaries. FRONTS
– What causes air masses to move across
the Earth?
I. Weather Maps
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Answer: Planetary winds
I. Weather Maps
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D. Weather Fronts
– There are usually several different air
masses moving across the United States.
– When different air masses meet, very
little ______ occurs.
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There is a frontal boundary and there is a
rapid change in the weather. It is usually
unsettled and rainy.
1. Weather Maps
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D. Weather Fronts
– There are 4 main types of frontal
boundaries
– 1. Cold Fronts occur when cold air moves
in on warmer air.
The cold air is more dense and stays near the
ground as it pushes up the warmer air in its
way.
 The warm air that is pushed up cools. It can
no longer hold as much water vapor and
heavy precipitation occurs.
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I.
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Weather Maps
D. Fronts
2. Warm Fronts occur when a warm air
mass runs into a cold air mass.
The warmer air is forced up and it cools.
It can no longer hold as much water
vapor.
Heavy precipitation occurs.
I.
Weather Maps
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D. Fronts
3. Stationary Fronts occur along the
boundary between a warm air mass and a
cold air mass when neither move.
– The warm air will eventually move on top of
the cold air and there will be precipitation for
a few days until a new front moves in.
I. Weather Maps
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D. Fronts
4. Occluded Fronts occur when a cold
air mass runs into another cold air
mass (a warm air mass might be stuck
between them).
– Since cold air masses are more dense,
they travel faster.
– Large scale precipitation occurs.
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I. Weather Maps
E. Cyclones are low pressure systems.
I.
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Weather maps
F. Anticyclones are high pressure systems.
I. Weather maps
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G. Jet Streams are bands of easterly
moving air made by convection cells
within the atmosphere. The winds can
blow up to 200 mph. Jet streams help
steer weather patterns across our
continent.
II. Weather Forecasting
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Synoptic weather forecasting uses
charts, maps and computers.
Statistical weather forecasting looks at
past weather frequency.
Weather patterns become evident
when weather variables are observed,
measured and recorded.
II. Weather Forecasting
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_________ is Radio Detection And
Ranging bounces electromagnetic
energy off of clouds to get images on
a computer
Doppler Radar is a special type of
radar that gives accurate readings and
is able to determine the conditions
necessary for tornadoes
II. Weather Forecasting
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_____________ images show the position of
clouds and storms as they travel over the
earth.
III. Energy in the Atm.
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Earth’s systems have internal and
external heat engines
– Internal: friction, radioactivity, residual
heat from formation
– External: sun’s heat, trapped Earth’s heat
III. Energy in the Atm.
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Precipitation results from the heating of the
atmposphere from the sun.
The transfer of energy from the
atmosphere, hudrosphere and th eEarth’s
interior results in the formation of regions
with different densities.
Density differences between regions results
in the motion of air and weather.
IV. Hazardous Weather
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The loss of property, personal injury
and loss of life can be reduced by
effective emergency preparedness.
IV. Hazardous Weather
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Thunderstorms
– Updrafts and down drafts of air occur
because of unequal heating
– Particles of air build up electrical charges
as the air goes up and down
– Lightening occurs because of the electrical
charges
– **Stay away from trees, don’t use
electrical appliances, don’t use plumbing
IV. Hazardous Weather
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____________ are small, brief
disturbances that usually develop over
land from intense thunderstorms
– Hot moist air meeting with cold, dry air
– Narrow: 100 feet in diameter
– Can last up to an hour
– Wind speeds up to 320 mph
– Occur in spring and summer
– ****Go into the basement and cover
your head, stay away from windows.
IV. Hazardous Weather
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________________ are regions of very
low pressure, cyclones, that form over
open water, huge swirling wind mass
Lose energy as travels over land
Winds of 74 mph or more, storm
surges, causes massive flooding
June to November
***Evacuate