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97 Cards in this Set
- Front
- Back
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Atmosphere composition (dry air)
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N - 78% O - 21% Ar - 1% |
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Percentage of air that is water vapour
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1-4% in lower atmosphere
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What are the properties of the atmosphere that cause all weather?
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-Mobility -Expansion -Compression |
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What are the layers of the atmosphere
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-troposphere -stratosphere -mesosphere -thermosphere |
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Properties of troposphere
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-closest to earth, affected by heating from the ground -contains 75% of atmosphere's mass -height varies with seasons and proximity to equator (11-17km) |
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Properties of stratosphere
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-Where majority of UV absorbtion takes place, and so it heats with altitude. -No turbulence, excellent vis. |
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Properties of mesoshpere
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temp begins to fall with alt again
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Thermosphere
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-air particles are extremely hot, but there are so few of them that is would not be felt. -highly dependent on solar activity. |
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Where in the atmosphere are winds hightes? How hast do they get? |
-just before tropopause (jet streams) -60 to 200kts |
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From where does moisture in the atmosphere oridinate? Where is its concentration highest? |
-bodies of water -plant transpiration -sublimation from snow or ice Highest near its source |
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What determines how much water air can hold? |
temp (higher temp -> more water) |
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What are dew point and relative humidity? |
Both measure the humidity of the air. -Dew point: the temperature at which the air would be 100% saturated. -Relative humidity: the percentage that the air is saturated. |
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What is nocturnal inversion? What is it affected by? |
at night the earth radiates into the atmosphere, but does not fo beyonf the first few thousand feet. The earth cools the air near its surface, and this causes temp to rise with alt for a certain distance. -Wind-causes mixing, lessening the effect -Cloud-reflects the radiated heat back to earth, lessening the effect. -Topology-slopes can cause the cooled air to pool in valleys, increasing the effect. -Water-cools less, reducing the effect. |
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Processes that can lift air
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-orthographic lift (wind blowing up a slope) -mechanical turbulence (wind blown across rough terrain stirs it up, causing it to ascend in the process) -convection -frontal lift (aka large scale ascent) |
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what is advective cooling? Evapourative cooling?
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Advective: warm air blows over a cool surface, cooling and becoming turbulent, which leads to mixing Evapourative cooling: Precipitation cools below as it falls through it. |
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What are the ways the atmosphere is heated? What process is responsible for heating in the troposphere?
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-UV ray absorbtion in the stratosphere -IR absorbtion by vapour and CO2 (IR comes from the earth, which converted it from UV and visible light). -Direct conduction from the earth's surface which is then convected upwards (MAJORITY) |
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How is air mixed in the atmosphere?
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-convection -turbulent mixing -advection (cool air moves warm surface; conducts and becomes turbulent) -compression (air in a low system or down a mountainside) -latent heat (given off when vapour condenses) |
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What is an air mass? Name the ones of interest.
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-A large body of air with similar charicteristics. -cA, cP, cT (all dry, only T is unstable) mA, mP, mT (all moist and unstable) |
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What is convective mixing>
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When air is warmed by the earth's surface and rises, carrying with it temp and humidity. |
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What is the effect of cooling from below?
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The cooler air cannot rise to carry its characteristics to the rest of the mass and is confined to the lower few thousand feet.
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Where do air masses come from?
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All air masses start as either cP, cT, or mT. cP: -Some cP air moves into the pacific, where it becomes moist and warmed near the surface. The result is mA air (very turbulent); when the moisture and heat has mixed all the way up to the tropopause, it has become mP. -Some cP air flows over the conteant. In the winter there is little effect (which is why cP becomes so large), in the summer it heats and picks-up some moisture, becoming cA. mT: Flows from the equator over NA, but NA is colder and so little mixing occurs and the characteristics are largely maintained as it moves over the continent cT: Formed over the US deserts. Rarely reach Canada. |
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What are fronts
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The boarder zones between air masses (air masses do not easily mix and instead remain fairly uniform.
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What causes a quasi-stationary front?
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A boarder between air masses, where the masses are moving parallel to each other, in opposite directions.
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What is an occluded front?
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lkmcx
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Types of fronts |
Warm, cold, quasi-stationary, occluded |
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what is the name for there area where 2 air masses meet? |
a frontal zone |
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what is a frontal inversion? |
where 2 fronts collide, there is a mixing zone along where the 2 surfaces meet. Here, air gets warmer with altitude as you pass from the cold to the warm mass, then once in the warm mass, temp decreases with altitude again. |
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what happens to the tropopause if a cold air mass reaches all the way to the stratosphere? |
it drops over the cold air mass |
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What are typical frontal slopes for quasi-stationary, warm, and cold fronts? |
QS - 1 deg warm - .5 deg cold - 1.5 deg |
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What is a fast cold front an what property does it have? |
A very fast front for which surface friction is high can develop a prodruding nose in the lower few thousand feet. |
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What determins the movement of a front? |
The wind direction of the cold air mass perpendicular to the front. |
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What can a steady drop in pressure indicate? |
A coming front |
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When reading isobars, what is a trough? ridge? col? |
trough - elongated area of low pressure ridge-elongated area of high pressure col - area between 2 highs and 2 lows |
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When a station reports pressure, what exactly is it reporting? |
The pressure at that point at MSL (i.e. not necessarily what is actually read). |
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What is the pressure difference between isobars on a standard pressure map? |
4 isobars |
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define: gust squall veer back |
gust - rapid peaks and lulls (<2 min) squall - rapid onset of strong winds lasting >2 minuets (often several; graual easing, assio with CBs) veer - clockwise change in wind direction (assiociated with ascents and stronger winds) back - opposite of veer |
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What is Pressure Gradient Force? |
The force which tends to move air form high pressure areas to low pressure areas. |
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Is higher wind speed assiociated with close isobars or distant isobars? |
close (i.e. strong pressure gradient)
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what is corolis force? |
caused by the rotation of the earth, it causes air in motion to diflect oteh right in the northern hemisphere. Air typically continues to be deflected to the right until the coriolis force and pressure gradient force are in equalibrium, at which point the air is traveling parallel to the isobars. |
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What is Buys-Ballots' Law? |
In the northern henisphere, if you stand with the wind to your back, then low pressure is on your left. |
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What are Boundary Layer Winds? |
winds in the lower atmosphere, close to the surface of the earth. They are affected by terrain and bear little resemblance to the isobar patterns. |
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Name some winds that can can be encountered in mountainous terrain |
funnel - operning in obstruction; and be +80kts anabatic - upward, heating catabatic - downward, cooling galcier - katabatic + glacial cooling Chinooks - mountain waves redirect warm air down the rockies (it usually rides above the cold air near the surface), heating the praries. |
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Which are stronger: land or sea breezes? |
Sea. |
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What are the three large-scale circulation cells (North to euqator)? |
Polar
Ferrel Hadley |
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What are three types of wind above the boundary layer? |
Thermal wind (tendancy of air to move from Tropospheric wind (jet streams) Lower stratospheric wind??? |
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What winds prevail in the middle latitudes of the northern hemisphere? |
southwesterly |
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What are the severities of turbulence (least to most severe)? What are some keywords acciocuated with each?
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Light Turb - "slight". No difficulty walking Light Chop - "slight". No difficulty walking Moderate Turb - "slight + rapid, A/C remains in control". Walking difficult Moderate Chop - "rapid bumbs, no appreciable change in alt". Walking difficult Severe Turb - "large changes in alt, A/C out of control". Violent for passangers. *"rhythmic" = chop |
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Types of turbulance
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-Mechanical (wind hitting obstructions causes eddies) -Convective (passing into a large cell of ascending air; in and below cumulous type clouds; worse for fast moving aircraft) -Clear Air Turbulance (above boundary layer and not adjacent to convective activity. Due to wind shearing, common around jet streams. Short lived <1 hour) -Wake Turbulence (cones projecting downward and out from wingtips. Decent to 900ft below aircraft, move Often cause roll) |
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How fast does wake turb decent, how low does it level off, how quickly does it spread?
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decent: 400-500fpm level off: 800-900ft spread: 5kts near ground |
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Types of precipitation charicter
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-showers (abrupt start/stop, short duration, brithtening sky in between, culouloform clouds) -intermittent (not showers but stop/start at least once in an hour) -continuous (no break for at least an hour) |
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Conditions for contrails? Types of contrails?
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Conditions: cold, humid air Types: -Exhause (humidity from engines) -Aerodynamic (pressure drop above lifting surface drops temp, forcing cooling |
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What can be done to avoid creating contrails?
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-fly high in stratosphere (dry air) -fly at a level where the air is warm -avoid sirrius cloud (indicated moisture) -reduce throttle |
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Four families of cloud?
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High (cirrus, cirrostratus, cirruculoulus) Middle Low Vert Dev |
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High level clouds (and height) (and primary composition) |
Cirrus (wisps or streaks) Cirrostratus (high level fog) Cirrocumulus (high puffy layer) (all 20 000ft+) (composed of ice crystals) |
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Med level clouds (and height) (and primary composition)
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Altostratus (med level fog) Altocululous (med level puffy layer) Altocumulous Castelanous (ACs with upturned "turrets") (all 6000-20 000ft) (composed of ice crystals and water droplets) |
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Low level clouds (and height)
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Stratus (fog that does not tough the ground, very low) Stratus fractus (fractured stratus) Nimbostratus (rain cloud - dark, continuous precipitation maybe falling) Stratocumulus (rolling, wavy, low level cloud. May be broken up or not) |
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Clouds of vert development |
Cumulus (puffy, but not part of an overall surface) Cumulus Fractus (ragged or wispy) Towering Cumulus CBs |
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Factors affecting cloud development
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condensation nuclei moisture stability (stable = whispy, unstable = pufft) rate of cooling (high = more cloud) |
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Dry air lapse rate, Saturated air lapse rate |
Dry: 3 deg/1000ft Saturated: 1.5 degrees / 1000ft |
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What are some things cause cloud formation?
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mechanical turbulence convection frontal lift orthographic lift (steep = unstable, gradial = stable) cyclonic (low flow into pressure lifts air) / anti-cyclonic (flow out of high pressure casuses air to decent) evaporative cooling (rain cools air, causing fog or stratus) advection (cooling by cold surface causes fog or stratus)
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What is frontogenesis / frontolysis? What is it associated with? What is the symbol for it? |
Frontogenesis: -The forming of a front -Associated with strong temp gradient -Alternating semi-circles / triangles with gaps between Frontolysis: -The dissipating of a front -Associated with a weak temp gradient -Alternating semi-circles / triangles with gaps and line segments between. |
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When passing through a front, in what direction should you alter your course? |
Always to the right (passing through a front is always associated with a veer). |
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What are the temp ranges for stability? |
Stable: <1.5 degrees / 1000 ft Conditionally stable: between 1.5 and 3 degrees / 1000 ft Unstable: > 3 degrees / 1000 ft |
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What is potentially stable air? What is neutrally stable air? |
Potential - Will become unstable if disturbed. Neutral - Neither resists nor favors motion. |
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Is icing possible inside cirrus clouds? Alto clouds? |
Cirrus: No (too cold). Alto: Almost always. |
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What is min velocity for a ribbon of air to qualify as a jet stream? How fast must a jet stream be to appear on SIG WX charts? |
Min velocity to qualify: 90 kts SIG WX: 80 kts |
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Where in a frontage system is a jet stream located? Where is there turbulance? |
-Located in warm air mass, just below the TROP. -Turb above and on the low-trop side. |
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Around what speed will a jet stream cause turbulance? |
~110 kts |
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What should be done to minimize frontal turbulence? |
Temp up -> climb Temp down -> decent |
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At what wind speed can mechanical turbulence occur? |
>3 kts |
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Bregeron Effect? |
sublimation? |
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2 World Area Forcast Products |
-high level SIG WX -Digital Winds |
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What do the Aviations Services and Defence Services branches of Env Canada do? |
Aviation Services - Provide info and services to Nav Canada Defence Services - Provide info and services to DND |
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What is an airmet? |
Basically an ammendment to a GFA. |
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What is a SIGMET |
A significant meteriological develpoment notice for airmen in the air. It superseeds all other aviation weather products while in effect. |
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When is RVR reported? |
When vis < 1 mile or RVR <6000 ft |
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What does VC mean in a TAF? In a METAR? |
TAF - 5 to 10nm from center of aerodrome METAR - Withing 5 miles but not at airdrome |
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How is wind shear (WS) reported in a TAF? In a METAR? |
TAF - Reported in 100s of feet up to ____
METAR - Just reported if present. |
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What is VB? |
Turbulence penetration speed - slow enough no to over-stress the aircraft but fast enough to avoid stalling.
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What are lee waves? |
Caused by mountains. |
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which move faster: high or low pressure systems? |
Low pressure |
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Define occasional, intermittent, and continuous turbumence |
intermittent - 1/3 to 2/3 of the time. |
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what wind speed is required for CAT? |
50 kts
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What type of aircraft causes the most turbulence? |
Heavy, clean, slow |
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What 3 things affect the intensity of lee waves? |
-Barrier size -Wind direction (within 30 degrees) and speed (15 kts for small ridges, 30 kts for larger ones) > strongest with perpendiculat jet streams -Stabile air around the barrier (possibly less stable around the peak) |
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3 types of lee wave clouds |
-cap -lenticular (near the crest of the wave) -rotor (balls downstream) > MOST intense turbulence |
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Hazards of Lee Waved |
-vertical currents -Icing -Altimeter errors |
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At the crest of a lee wave, how does the wind change? Max alt? Max range? |
increases, 70 000ft, 300 miles |
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What are the charicteristics of different CBs at different types of fronts? |
Cold Front - Most severe, squall lines. Warm Front - Least severe, embedded. Occluded Front - Medium severity, embedded. |
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How do nocturnal CBs develop? |
Mid-west, over water at night. |
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Can troughs start squall lines? |
Yes. |
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What are the stages of CBs? |
Cumulus, mature (precipitation begins, 15-20 min typical), dissipation (turn to stratus, 1-2 hours) |
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Typical shears around jet streams? |
Horizontal - 5-20 kts / 1000ft Vertical - 24-100kts / 100 miles |
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What season are jet streams strongest? |
Summer |
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Where do nocturnal jet streams develop? Max height? |
near tops of inversions over flat terrain; 2000ft AGL |
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Max altitude of a GFA |
24000 ft |
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What are the intervals of freezing level lines on a GFA? |
2500ft |
