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86 Cards in this Set
- Front
- Back
Identify each arrow
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How is wind direction expressed?
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the direction from which it is blowing
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What is a station model?
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Method to annotate wind on a chart
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What are the left two numbers and middle marker on a station model?
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Temperature (top) and Dew Point (bottom). Present weather may be in middle.
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What are the right two numbers on a station model?
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Sea Level Pressure (top) and Pressure Change over the last three hours (bottom)
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What does the flag indicate on a station model?
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Wind direction and speed - Pennant = 50kts, long barb = 10kts, short barb = 5kts
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What does the circle / square indicate on a station model?
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Sky Cover in eigths, square = automated, circle = manual
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On the station model chart, what does the dot, comma, or star mean?
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Rain, Drizzle or Snow
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On the station model chart, what is the sea level pressure expressed in?
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3 digits to represent tenths of millibars
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On the station model chart, what is the time frame of the pressure change?
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past three hours
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Which direction does wind flow around high pressure areas?
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clockwise
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Which direction does wind flow around low pressure areas?
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counterclockwise
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What does the spacing of isobars indicate?
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Rate of pressure change = pressure gradient = pressure gradient force (PGF)
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What causes the Coriolis force?
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Earth's rotation
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What does the Coriolis force do?
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Diverts air to the right with respect to its initial direction of motion
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Where are gradient winds found?
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Above 2,000 feet
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How do gradient winds flow?
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Parallel to Isobars, CCW around Lows, CW around highs
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When must surface friction be considered in determining wind direction?
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Below 2,000 feet
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What are the 3 forces that must be balanced below 2,000ft to determine wind direction?
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PGF, Coriolis force, and Friction
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What is Buys Ballot's Law?
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If the wind is at your back, the area of low pressure is to your left (slightly forward of left if standing on the earth's surface
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Where is the Jet Stream?
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around 30,000 feet
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What are the wind speeds of the Jet Stream?
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Over 50 kts, usually 100-150 kts, up to 250 kts
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How big is the jet stream?
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1000-3000 miles long, 100-400 miles wide, 3000-7000 feet deep
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What happens to the jet stream in the winter?
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Moves south, higher, faster
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When does a sea breeze occur and where does it come from?
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Day, from sea, 15-20 kts
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When does a land breeze occur and where does it come from?
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Night, from land, faster and shorter than sea breeze
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When does a mountain wind occur and where does it come from?
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Night, from the mountain
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When does a valley wind occur and where does it come from?
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Day, from the valley
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When does saturation occur?
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When air contains a maximum amount of water vapor for a given temperature: dew point = air temperature
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What is the dew point?
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the temperature at which saturation occurs
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What does the dew point indicate?
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amount of mosture in the air (potential)
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What happens with a higher dew point / narrow dew point depression?
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visible moisture in the form of dew, frost, fog or clouds
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What is the RH when the dew point spread reaches 4 degrees F?
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90%
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What are three characteristics of precipitation and corresponding cloud type?
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Showers (cumuliform), Continuous (stratiform), Intermittent (cumuliform or stratiform)
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What are common types of precipitation (7 listed)?
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Drizzle, freezing drizzle, rain, freezing rain, hail/graupel, ice pellets/sleet, snow/snow grains
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What are clouds made of?
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Condensed water vapor, consisting of water droplets or ice crystals
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What are condensation nuclei?
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Dust, salt crystals, ash, particles, etc. that water vapor can condense upon to create clouds
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What are the four groups of clouds?
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Low, Middle, High, Special
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What is the height range of low clouds?
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Surface to 6,500' AGL
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What is the height range of middle clouds?
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6,500' to 20,000' AGL
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What is the height range of high clouds?
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Above 20,000' AGL
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What is the height range of special clouds?
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Extensive vertical development, usually from low to middle clouds through high cloud category
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What determines the classification of clouds?
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The cloud base
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What are the two prinicpal cloud forms?
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Cumuliform and Stratiform
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What is a cumuliform cloud?
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Lumpy & billowy with a definite pattern/structure to the base
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What is a stratiform cloud?
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Uniform base with horizontal sheet-like layers
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What is the primary composition of low clouds?
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Water droplets
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What is the special prefix attached to low clouds?
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No special prefix attached
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What does the prefix nimbo or numbus indicate?
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Violent or heavy precipitation
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What type of cloud is a nibostratus cloud and what type of precipitation does it produce?
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A stratiform cloud that produces heavy steady precipitation (Low cloud in example)
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What are risks of low clouds?
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Visibility of terrain, faster icing, low turbulence, light precipitation
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What is the primary composition of middle clouds?
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Ice crystals, water droplets or a mixture of the two
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What is the special prefix attached to middle clouds?
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Alto-
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What is visibility in middle clouds?
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1/2 mile to a few feet
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What are risks of middle clouds?
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Low visibiltiy, turbulence, icing, rain and snow
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What is Virga and where is it found?
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Rain or snow that evaporates before reaching the ground; can be encountered below middle clouds
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What is the special prefix attached to high clouds?
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cirro- or the word cirrus
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What are characteristics of high clouds?
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Little effect, moderate turbulence, limited visibility, no precipitation, not an icing hazard
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What is the primary composition of high clouds?
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ice crystals
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What types of clouds are included in the Special Clouds with Extensive Vertical Development?
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Towering cumulus and cumulonimbus
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What type of clouds are shown in Figure 2-14?
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Stratus
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What type of clouds are shown in Figure 2-15?
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Altocumulus
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What type of clouds are shown in Figure 2-16?
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Cirrus
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What type of clouds are shown in Figure 2-17?
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Cumulonimbus
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What are the risks of towering cumulus clouds?
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Nearing the thunderstorm stage, heavy rain, moderate tubulence, icing
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What are the risks of cumulonimbus clouds?
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Thunderstorms, extreme turbulence, hail, icing, lightning
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What type of weather stability does Figure 2-22 (left) indicate (colder air settling when lifting action is removed)?
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Stable condition
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What type of weather stability does Figure 2-22 (middle) indicate (air is pushed up and continues to rise)?
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Unstable condition
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What type of weather stability does Figure 2-22 (right) indicate (air is pushed up and stays at that level)?
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Neutral
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What are the four methods of lifting?
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Convergence, frontal, orographic and thermal
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What is Convergence?
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Two air masses converging and forcing air upwards
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What does a cold front Do as it moves through an area?
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Lift the air ahead of the cold air mass
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What is Orographic lifting?
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Force of the wind against a mountainside pushing air upward
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What is thermal lifting?
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convective lifting, cool air heated by a warm surface and pushed upward
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Identify the four lifting methods in Figure 2-23
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Convergence, frontal, orographic and thermal
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What stability conditions do cumuliform clouds indicate?
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Unstable conditions
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What stability conditions do stratiform clouds indicate?
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Stable conditions
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What type of turbulence indicates stable / unstable atmosphere?
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Smooth / Rough
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What type of visibility indicates stable / unstable atmosphere?
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Poor / Good (outside clouds)
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What type of winds indicates stable / unstable atmosphere?
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Steady / Gusty
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What type of precipitation indicates stable / unstable atmosphere?
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Steady / Showery
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What type of icing indicates stable / unstable atmosphere?
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Rime / Clear
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What type of air mass indicates stable / unstable atmosphere?
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Warm / Cold
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What type of front indicates stable / unstable atmosphere?
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Warm / Cold
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What are additional signs in the sky that indicate stable air?
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Temperature inversions, low fog, stratus clouds
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What are additional signs in the sky that indicate unstable conditions?
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Thunderstorms, showers, towering clouds, dust devils, rapidly decreasing air temperature while climbing
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