Related Essays

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/301

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

301 Cards in this Set

  • Front
  • Back
A thin layer of transition between stratosphere and mesosphere.
STRATOPAUSE
Excellent flying conditions exist because of a lack of weather in this
layer.
STRATOSPHERE
All our weather occurs in this layer/zone.
TROPOSPHERE
This layer has an average lapse rate of 6.5°C per 1,000 meters.
TROPOSPHERE
Contains the “E” and “F” layers.
THERMOSPHERE
Noctilucent clouds occur in this layer/zone.
MESOSPHERE/
THERMOSPHERE
Contains most of the ozone of the atmosphere.
STRATOSPHERE
Layer of the earth’s atmosphere extending from 262,000 feet to
infinity.
THERMOSPHERE
The nacreous, or mother-of-pearl cloud, occurs in this layer.
STRATOSPHERE
Average height of this layer, over the equator, is 10 miles.
TROPOPAUSE
Contains the “D” layer.
MESOSPHERE
An unstable layer of the earth’s atmosphere.
TROPOSPHERE/
MESOSPHERE
A thin layer of transition between the troposphere and stratosphere.
TROPOPAUSE
A thin layer of transition between the mesosphere and
thermosphere.
MESOPAUSE
Over the poles, average height of this layer is 5 miles.
TROPOPAUSE
Contains layers of electrons that reflect radio waves.
MESOSPHERE/
THERMOSPHERE
Occupies 21 percent by volume of the atmosphere.
OXYGEN
Occupies 1.2 percent by volume of the atmosphere.
WATER VAPOR
Occupies almost 1 percent by volume of the atmosphere.
ARGON
Occupies 78 percent by volume of the atmosphere.
NITROGEN
Occupies 0.03 percent by volume of the atmosphere.
CARBON DIOXIDE
The most important gas to meteorology.
Oxygen
(somehow not water vapor?)
The amount of this gas varies with the seasons.
CARBON DIOXIDE
The colder the air, the less of this gas there is in the air.
WATER VAPOR
Maximum quantities are found in the stratosphere.
OZONE
The more of this gas the air holds, the lighter it will be.
WATER VAPOR
This gas is at a maximum around cities and industrial regions.
CARBON DIOXIDE
Four percent by volume is the maximum amount of this gas the air
can hold.
WATER VAPOR
This absorbs ultraviolet radiation.
OZONE
All weather clouds and precipitation are produced by this gas.
WATER VAPOR
This layer prevents the sun from burning up the earth.
Ozone.
What’s the catalyst for the formation of weather?
The manner in which the earth’s surface is heated (differential heating).
As the angle of incidence increases, what happens to the concentration of solar radiation?
It decreases.
Name the two motions of the earth that have an effect on weather.
Rotation and revolution.
The angle of inclination combined with the revolution of the earth around the sun causes what
events?
The seasons.
When an equinox occurs, where is an equal amount of sunshine received?
In both hemispheres.
What two atmospheric gases are responsible for absorbing incoming solar radiation?
Oxygen and ozone.
Which wavelengths are most susceptible to atmospheric scattering?
The shorter wavelengths, particularly where particles are less than 0.5 microns.
Approximately how much of the incoming solar radiation is absorbed by the atmosphere?
20 percent.
Approximately how much solar radiation is reflected by the earth’s surfaces?
3 percent.
Briefly describe conditions that cause a single-cell circulation pattern.
Single-cell circulation is the result of differential heating of a nonrotating earth with a smooth surface.
What’s the main driving mechanism responsible for the earth’s large-scale atmospheric
circulations?
Unequal heating of the earth.
Strong easterly surface winds are found beneath this cell.
Polar Cell
A strong Coriolis force sharply alters wind direction.
Polar, Ferrel Cells
Circulation in this cell is interrupted by the exchange of polar and tropical air.
Ferrel Cell
The cell most responsible for subtropical belt of high pressure.
Hadley Cell
Northeast trade winds are found beneath this cell.
Hadley cell
The cell dominated by westerly flow at the surface and aloft.
Ferrel cell
Strongest of the three cells.
Hadley cell
Generally located between 30 and 60°.
Ferrel cell
The cell created by rising equatorial air.
Hadley cell
Mean position is between 60 and 90°.
polar
Upper-level flow in this cell is deflected eastward.
Hadley
Which force is any force that causes a body to veer from a straight path?
Centripetal force.
If a bucket of water is swung perpendicular to the ground, what force keeps water in the bucket
from falling out even when the bucket is upside down?
Centrifugal force.
In circular motion, what force acts against the inertia of the moving object?
Centripetal force.
What force causes objects to veer from their intended path on a rotating platform?
Coriolis force.
What force is the equal and opposite reaction to center-seeking forces?
Centrifugal force.
What force appears to cause objects in the southern hemisphere to be deflected to the left of their
intended path?
Coriolis force.
What are the four forces that dictate the general circulation pattern?
(1) Coriolis.
(2) Centrifugal.
(3) Frictional.
(4) Pressure gradient.
Which force starts the horizontal movement of air over the earth’s surface?
Pressure gradient.
Describe contour gradient force.
The force that represents PGF on a constant-pressure product. It’s the rate of height change with change in
distance on a constant-pressure surface.
What kind of flow is created when PGF equals CoF?
Geostrophic flow.
What does Buy Ballot’s law state?
In the Northern Hemisphere, if the wind is at your back, lower pressure is to your left and higher pressure is
to your right.
What can a pilot expect the wind direction and speed to do as the aircraft descends into an area
with rough terrain? Why?
The wind direction will back and the wind speed will slow due to increased friction.
What’s the difference between confluence and difluence?
Confluence is the merging of wind flow, whereas difluence is the spreading apart of wind flow.
Where do winds deflect towards in a supergradient wind condition and what’s happening to the
air parcels?
Towards higher heights; the parcels are converting kinetic energy to potential energy.
A hurricane is an example of what kind of wind?
Cyclostrophic.
Dominates the Atlantic Ocean west of Africa.
Semipermanent; high.
Most prevalent over the oceans of the Southern Hemisphere during January.
Semipermanent; high.
Dominates Asia during the winter.
Semipermanent; high.
Located in the North Atlantic Ocean near Greenland.
Semipermanent; low.
Dominates the continents of the Southern Hemisphere during January.
Semipermanent; low.
In the summer it’s located east of the Persian Gulf near 23°N.
Semipermanent; low.
The influence of the Polar high makes it less prevalent in the summer.
Semipermanent; low.
Fair weather is associated with this system in the middle latitudes.
Migratory; high.
Lack of land masses near 60°S allows this to remain as a somewhat constant belt of pressure.
Semipermanent; low.
Found as an extension of another feature and is located off the Southeast Coast of the United
States.
Semipermanent; high.
Briefly define a jet stream.
The jet stream is a narrow belt of strong winds, with speeds of 50 to 200 knots, in the upper troposphere.
How does the jet stream vary in latitude and altitude around the world?
Jet stream position varies between different latitudes and elevations around the earth. It even varies in
latitude and elevation within a small geographical area. The jet stream may appear as a continuous band
around the earth, but more often it gradually diminishes at one or more points and then reappears farther
downstream.
Two major jet streams are frequently observed. What are they?
The PFJ and the STJ.
Of the horizontal or vertical wind shears associated with the jet stream, which is the stronger?
The vertical wind shear associated with the jet stream is much stronger than the horizontal.
Where does the greatest vertical wind shear occur with respect to the jet core?
Immediately above the jet core.
Where does the greatest horizontal shear occur with respect to the jet core?
North of the jet core.
Jet stream found near the Arctic Circle.
Arctic/Polar night jet
stream.
Observed in the latitudinal range of 25 to 30°N near the 150-mb level.
Subtropical jet stream.
Jet stream which divides the tropopause into the polar and midlatitude
leaves.
Polar front jet stream.
Summertime jet stream found over southern Asia and northern Africa
at the 150-mb level.
Tropical easterly jet
stream.
The jet streams which most affect the Northern Hemisphere.
Polar front jet stream, Subtropical jet stream.
What are the two primary causes of jet stream formation?
Large horizontal temperature contrast and conservation of angular momentum.
8 - 9
What’s the primary originator of the PFJ stream?
Horizontal temperature contrast.
In relation to the 500-mb surface, where is the PFJ core usually found?
The 500-mb isotherm ribbon.
Along what isotherm does the PFJ intersect the 500-mb surface?
–17°C
At what altitude do you usually find the jet stream core during the winter?
29,400 to 30,300 feet.
The width of the jet core is approximately equal to what isotherm ribbon?
500-mb.
What factor accelerates the STJ?
Conservation of angular momentum.
What might a wedged-shaped cloud pattern seen on satellite imagery over Texas indicate? What
causes this pattern to occur?
Severe weather. The interaction of the PFJ and the STJ.
The longitudinal axis tends to follow the long-wave pattern.
Organized.
The wind gradient along the axis becomes very strong (often exceeding 100 knots).
Organized.
Jet fingers are formed often and about 300 to 400 miles apart.
Disorganized.
Well-defined wind speeds of 50 knots or more disappear.
Disorganized.
The distance between isotach maxima is 10 to 25° longitude.
Disorganized.
The following series of statements represent events during the cycle of a jet stream migrating
northward. The statements are out of sequence. Arrange them in the proper sequence.
_____ a. A west wind maximum emerges from the Tropics.
_____ b. The jet stream is well-organized and often shows troughing into the low latitudes.
_____ c. A second maximum, located in the upper midlatitudes, moves northward and dissipates.
_____ d. The amplitude of the long waves decrease and a classical high index situation exists.
_____ e. Cut-off lows south of the prevailing westerlies dissipate.
The proper sequence should be: a=1, b=3, c=2, d=4, e=5.
How will the jet stream lie in relation to an occlusion and to a cold front oriented north-south,
with no associated warm front?
Perpendicular.
Where does the jet stream remain (north or south) in relation to an unoccluded wave cyclone?
North.
Does the jet stream lie north or south of the low associated with an occluded front?
South (near the point of occlusion).
Will the jet stream parallel the direction of the warm sector isobars of a surface low?
yes
Does the jet stream roughly parallel the isobars around the northern periphery of a warm (slowmoving)
surface high?
yes
When a cold surface high dissipates, what happens to the jet stream aloft?
The jet aloft usually dissipates.
List the four cloud patterns associated with the jet stream.
(1) Lines of cirrus in bands, (2) patches of cirrocumulus or altocumulus castellanus, (3) lenticular clouds in
waves, and (4) waves of altocumulus.
12 - 8
Where do clouds most frequently occur in relation to the jet core and the equator?
5,000 to 10,000 feet below the jet core and 4 to 5° equatorward.
Where do clouds most frequently occur in relation to the jet core and the poles?
10,000 to 15,000 feet below the jet core and 4 to 5° poleward.
Precipitation usually straddles the jet, with a slight bias toward which side of the jet?
Poleward side.
Explain Wein’s law.
The wavelength at which the maximum amount of energy is emitted by an object is inversely (directly
opposite) proportional to the temperature of the object.
What wavelength of the electromagnetic spectrum allows weather satellites to obtain imagery
during both day and night?
Infrared.
Why do calm, cloudy nights tend to be warmer than calm, clear nights?
Because clouds composed of tiny water vapor droplets are excellent absorbers/emitters of infrared
radiation.
Would thick clouds or a forest have a higher albedo? Why?
Thick clouds because they have a higher reflective capability.
What can be said about the earth in terms of absorption of solar radiation and emission of infrared
radiation?
The earth absorbs solar radiation only during daylight hours; however, it emits infrared radiation
continuously, both day and night.
Would soil or air have better heat conductivity? Why?
Soil, because it’s a better conductor of heat than air due to its molecular structure and density.
What’s convection?
The vertical transport of atmospheric properties (heat and moisture).
What can initiate convection?
Any individual occurrence or combination of: (1) surface heating, (2) low-level convergence, (3)
orographic effects, and (4) frontal lift.
What’s advection?
The horizontal transport of atmospheric properties such as heat.
Name the three factors needed for air mass formation.
A surface that has comparatively uniform properties.
Stagnant air over the uniform surface.
A large divergent flow.
Most effective method of creating temperature equilibrium in an air mass.
Turbulent-convective transport.
Slowest method of creating temperature equilibrium in an air mass.
Radiational cooling.
Fastest method of creating temperature equilibrium in an air mass.
Turbulent-convective transport.
Not an effective method of creating temperature equilibrium in an air mass by itself.
Evaporation and condensation.
Effective method of creating temperature equilibrium in an air mass in polar regions
Radiational cooling.
Why are anticyclonic systems excellent for formation of air masses?
They have stagnant or slowly moving air, with divergent airflow and turbulent-convective mixing.
Why are cyclonic systems poor for forming air masses?
They have strong winds, convergent wind flow, and comparatively fast-moving systems.
Define air mass.
A widespread body of air identified horizontally by temperature and moisture characteristics.
What specific characteristics do air masses acquire when they form over oceans?
Mild temperatures, considerable moisture in the lower layers, moderate lapse rates, and a degree of
conditional instability.
Formed just south of Iceland during winter and is now over USSR. It is unstable.
mPwu.
Formed over Canada during winter and is now over US. It is stable.
cPks.
Formed over Brazil during summer and is now moving toward the equator. It is unstable.
cTwu.
Formed in Atlantic east of Bermuda during winter. Now over SE US; it is unstable.
mTwu.
In what air mass can ice fog form?
Wintertime continental polar air mass.
Which air mass is moist and unstable in the lower layers and cold and dry aloft?
Wintertime maritime polar air mass.
Which air mass is hot, dry, and unstable?
Continental tropical air mass.
This air mass is very moist, very warm and noticeably unstable.
Summertime maritime
tropical.
7-a
Found over open oceans at high latitudes.
Wintertime maritime polar.
Summertime maritime
polar.
Exceptionally cold, stable and very dry air mass.
Wintertime continental
polar.
Lapse rates in the lower levels often approach the dry adiabatic
lapse rate.
Wintertime maritime
tropical.
Cool and moist in the lower layers, and cool and dry aloft.
Summertime maritime
polar.
Similar to the upper-level sinking air that flows out of the
subtropical anticyclones.
Continental tropical.
Cool and dry, but not necessarily stable.
Summertime continental
polar.
Source region in the southwestern Caribbean.
Wintertime maritime
tropical.
Moist and unstable in the lower layers and cool and dry aloft.
Wintertime maritime polar.
Source region is the central portion of high-latitude continents.
Summertime continental
polar.
mPw air mass moving from Oregon to Wyoming.
Turbulent mixing, air mass moving over different terrain.
Summertime continental
polar.
Thermodynamic, cold air moving over warmer land.
mTw air mass moving from Gulf of Mexico into the southern US.
Thermodynamic, warm air moving over cooler land.
cPw air mass moving across the Great Lakes.
Thermodynamic, warm air moving over cooler water.
cPw air mass stagnant over Illinois at night.
Thermodynamic, nocturnal radiation.
mTw air mass moving from South Atlantic Ocean to North Atlantic Ocean.
Thermodynamic, warm air moving over colder water.
A high pressure moving over the central US from southern Canada.
cP—It’s cold (or cool depending on the time of year). The lower portion of the air mass undergoes slow
modification and become less stable, with the effects extending through a relatively deep layer.
Air over the southern Atlantic moves over the southeastern US via the Gulf of Mexico.
mT—The characteristics are warm and moist. The amount and type of modification depends upon the
time of year. In summer the land will be warmer and the lower portions less stable. In winter the land
may be cooler, resulting in the lower portions of the air mass becoming more stable.
Air from northern Canada moves over the midwestern US, which is already under cold air.
A—The arctic air will be cold and dry, with slight warming in the lower levels. In this type of air mass,
the stability decreases slowly. However, since the air is dry, good visibility’s prevail.
Air that originally was over the southern North Pacific that has moved over northwestern US
by way of the Gulf of Alaska.
mP—This air mass was probably mT. Now it’s modified enough in the lower portions to reclassify it as
mP. It will be relatively stable and moist in the lower levels. The amount of modification that takes place
as the air mass moves into the northwestern US depends on the time of year. During all seasons, the
moisture is lost as it moves on shore and over the mountains.
Air that has stagnated over equatorial oceans.
E—Equatorial air is slightly warmer than mT and slightly less stable.
Air that moves over the Mediterranean from northern Africa.
cT—This air mass is warm and dry. Although the air receives moisture rapidly, it does so only in a
shallow layer. Therefore, a shallow layer of unstable air exists under a stable layer.
Define horizontal divergence and horizontal convergence.
Horizontal divergence refers to the spreading out of air. When this occurs, the air moves away from the
center of the column. The original column of air contracts vertically and expands horizontally. In contrast,
horizontal convergence refers to the packing or bringing together of air. The air converges horizontally
toward the center of the column. The original column of air contracts horizontally and expands vertically.
State how divergence and convergence can change the surface pressure.
The pressure at the surface directly relates to the mass of air in the vertical column above the surface. The
surface pressure measures the net effect of the convergence and divergence.
What mechanism is believed to be the primary cause of the development of high and low pressure
areas?
Excess, or net divergence aloft for lows. Excess, or net convergence aloft for highs.
Cold-air advection into an upper-level low or trough will cause what intensity changes to theoretically occur?
a. It deepens the upper-level low/trough.
Warm-air advection into an upper-level high or ridge will cause what intensity changes to theoretically occur?
b. It builds the upper-level high/ridge.
What process creates the chimney effect? What happens to the mass in the column of air?
Net divergence; decreases.
What process creates the damper effect? What happens to the mass in the column of air?
Net convergence; increases.
Define wave cyclone.
An area of closed counterclockwise circulation occurring on a frontal surface.
Explain the difference between stable and unstable waves.
A stable wave has the amplitude decreasing or remaining the same with time and is usually filling or
showing no change in intensity. An unstable wave has the amplitude increasing with time and is usually
deepening.
Central pressure within a cyclone is decreasing.
Cyclogenesis.
Central pressure within a cyclone is increasing.
Cyclolysis.
The deepening of an existing cyclone.
Cyclogenesis.
The filling of an existing cyclone.
Cyclolysis.
Central pressure is rising more rapidly than the pressure around it.
Cyclolysis.
Central pressure is falling more rapidly than the pressure around it.
Cyclogenesis.
Intensity of the counterclockwise circulation increases.
Cyclogenesis.
Intensity of the counterclockwise circulation decreases.
Cyclolysis.
Where does an amplifying short wave extract energy during the baroclinic process?
From the north/south temperature gradient produced by differential heating.
What causes upper-level short wave amplification?
Large energy transfer (by means of thermal advection) from the temperature gradient to the wave.
How do short waves convert energy into low-level circulations?
By converting potential energy (transferred from the temperature gradient to the short wave) to kinetic
energy. The short wave uses the potential energy to develop the low-level circulation (kinetic energy).
What can be said about baroclinic instability and the development of midlatitude synoptic-scale
systems?
It’s the primary mechanism responsible for the development of midlatitude synoptic-scale systems.
What’s the relationship between the thermal wave and the contour wave during the baroclinic
process?
The thermal wave and contour wave are out-of-phase.
Where is cyclogenesis favored in reference to the long-wave pattern?
At and just downstream from a long-wave trough axis.
What’s the significance and orientation of a negatively tilted trough?
They cause stronger divergence and, therefore, support stronger cyclogenesis.
Under what kind of windflow aloft does cyclogenesis typically occur?
Difluent flow aloft.
Explain Petterssen’s rule.
Cyclogenesis occurs when and where an area of upper-level divergence (PVA) becomes superimposed over
a low-level frontal zone across which the thermal advection is weak.
What causes the surface low to deepen during the self-development process?
Divergence over the surface low.
How does boundary layer convergence contribute to the self-development process?
By acting as a breaking mechanism.
During the wave initiation stage, what’s associated with the short-wave trough that causes a wave
to form on a front?
Divergence.
During the wave intensification stage, what causes the upper-level short-wave trough to deepen?
What product supports this?
Cold-air advection; 500-mb product.
During what stage of low development does an occlusion occur?
Mature wave stage.
In what stage of development does a low that’s nearly vertically stacked and is continuing to
deepen occur?
Mature wave stage.
What type of circulation is associated with anticyclones in the Northern Hemisphere?
A closed, clockwise wind circulation.
How do the size and intensity of anticyclones compare to the size and intensity of cyclones?
Anticyclones are greater in size and generally of less intensity than cyclones.
Which anticyclones have the greatest horizontal and vertical extent?
Those anticyclones associated with the semipermanent highs.
The central pressure is increasing.
Anticyclogenesis.
An anticyclone’s circulation is weakening.
Anticyclolysis.
The central pressure is decreasing.
Anticyclolysis.
An anticyclone is forming.
Anticyclogenesis.
The clockwise circulation increases.
Anticyclogenesis
Has anticyclonic circulation that tilts toward the warm air with height.
Baroclinic high.
Has the warmest temperatures at its center and rarely extends above
10,000 feet.
Warm barotropic low.
Has the coldest temperatures at its center and has great vertical extent.
Cold barotropic low.
Combination of a frontal wave and an upper-air short-wave trough.
Baroclinic low.
Has the coldest temperatures at its center and rarely extends above
10,000 feet.
Cold barotropic high.
Has the warmest temperatures at its center and great vertical extent.
Warm barotropic high.
Review the following accurate statements concerning elements expected in the frontal zone.
c. Lapse rate through the frontal zone decreases sharply and dew-point curve increases sharply.
e. When precipitation falls through a subsidence inversion, the dew point may be raised enough
so that the inversion appears as a frontal inversion.
h. The winds back with height through a cold front.
k. The surface winds veer with passage of a warm front.
m. The surface winds are usually greatest behind both warm and cold fronts.
What conveyor belt is a set of streamlines that originates at low levels in the moist tropical air
mass?
Warm conveyor belt.
What conveyor belt originates in the low levels and is associated with subsidence well ahead of
the low center?
Cold conveyor belt.
24 4
Which conveyor belt originates at the upper levels?
Dry-air conveyor belt.
Slope of 1/75.
Cold front.
Warm air replacing cold air.
Warm front
Cold front aloft; warm front on surface.
Warm occlusion
Slope of 1/200.
Warm front
Warm front aloft; cold front on surface.
Cold front occlusion
Cold air replacing warm air.
Cold front
Cold air is parallel to the front.
Stationary
Name the five factors that determine the type and intensity of frontal weather.
a. The slope of the front.
b. The water vapor content.
c. Stability of the air masses.
d. Speed of the front.
e. The relative motion of air masses at the front.
Why does weather associated with a frontal passage differ from one place to another along the
same front?
Because air mass modifications and mixing create variations in characteristics within the air mass.
Slope 1/40 to 1/80.
Inactive.
Net windflow is up the frontal slope.
Inactive.
Net windflow is down the frontal slope.
Active.
Katafront.
Inactive.
Anafront.
Active.
Line of thunderstorms 100 miles ahead of front.
Active.
Thunderstorms and rain in immediate vicinity of front only.
Inactive.
Sharp temperature gradient with front.
Active.
Dew point and winds are best indicators of frontal passage.
Inactive.
At what speeds do warm fronts generally move?
10 to 15 knots.
How does the width of the warm frontal band of weather differ from that of either the inactive or
active cold fronts?
Weather occurs up to a several hundred mile wide band ahead of the surface warm front; even the active
cold frontal band of weather is much narrower.
Describe the situation in which thunderstorms develop with a warm front.
If the overrunning air is unstable, embedded thunderstorms are likely with the warm front.
Define the term stationary front.
A front moving less than 5 knots steadily in any direction.
Weather associated with a stationary front is similar to the weather found with what other type of
front?
It basically resembles warm front weather, but is in a somewhat narrower band.
With the approach of a warm front, what change should occur to the pressure, wind, temperature,
and dew point?
Pressure falls rapidly or unsteadily, wind velocity increases, temperature and dew point remain constant or
rise slowly.
On the 850-mb product, what’s the relationship between the warm front and the isotherms?
The isotherms will be packed ahead of the front and parallel to it.
Which regions of the United States have the most frontal occlusions?
The North—both the northwest and northeast portions.
In what season of the year are occluded fronts most common in the United States?
During the winter months.
If the air behind the cold front is colder than the air ahead of the warm front, what type of
occlusion will occur?
A cold frontal occlusion
What type of occlusion occurs when the air behind the cold front is warmer than the air ahead of
the warm front?
A warm frontal occlusion.
Where are the embedded thunderstorms with a cold frontal occlusion normally located?
The embedded thunderstorms occur with the passage of the surface occluded front.
Which type of occluded front normally has the wider cloud system?
A warm frontal occlusion.
What type of clouds and weather normally precede a cold occlusion?
Warm frontal clouds and precipitation.
With a cold occlusion passage, what will the pressure do?
Rise rapidly following passage.
As the occlusion process dissipates the warm front, what happens to the thickness gradient
associated with the surface front?
Thickness gradient decreases.
If a pilot descends vertically through a cold-type occlusion to pass through both fronts, how will
the wind switch?
The winds will first back, and then veer.
In a well-developed warm occlusion, what’s the relationship between the cold front portion and
the warm front?
The cold front will be aloft ahead of the warm front.
If showers and thunderstorms occur, where will they usually be located in relation to the front?
Ahead of and with the upper cold front portion.
State the characteristics usually occurring with warm-type occlusions:
a. Increased cloudiness as the upper front approaches.
c. Greatest clearing of clouds following upper front passage.
f. Steady rise of pressure following surface front.
g. Surface temperature rises following surface front passage.
If a pilot descends vertically through a warm-type occlusion to pass through both fronts, how
does the wind direction change?
First it will veer, and then back.
1. Indicate whether each of the following statements refers to frontogenesis or frontolysis:
a. Formation of a new front.
b. Dissipation of a front.
c. Intensification of a front.
d. Requires two air masses of different densities.
e. Prevailing wind brings the two air masses together.
a. Frontogenesis.
b. Frontolysis.
c. Frontogenesis.
d. Frontogenesis.
e. Frontogenesis.
Why are cols favored areas for frontogenesis?
Because the horizontal motions of the atmosphere in these areas contribute to sharp horizontal temperature
gradients.
What will a sharpening of the cyclonic turning do to a front?
Assists in maintaining or frontogenesizing the front.
How do diabatics support frontogenesis?
By heating the warm air or cooling the cold air.
How do diabatics support frontolysis?
By cooling the warm air or heating the cold air.
Name the three ways to measure frontal intensity by means of density contrast.
Thickness gradient, temperature gradient, and lapse rate.
What’s indicated by a negative lapse rate with a cold front in the vicinity?
This indicates that the cold front is strong.
What are two other ways to identify the strength of a front outside of density differences?
Turbulence and wind shear.
Classify the intensity of fronts having the following characteristics:
a. Temperature gradient 15°F/100 miles and thermal wind shear 65 knots.
b. Temperature gradient 8°F/100 miles and thermal wind shear 30 knots.
c. Temperature gradient 25°F/100 miles and thermal wind shear 85 knots.
a. Oderate.
b. Weak
c. Strong.
____ (1) A cloud of moderate or strong vertical development and doesn’t have a
cirriform top.
____ (2) Consists of clouds formed by means other than the spreading out of CU and
has clouds with bases at different levels.
____ (3) In its earliest stage of development, this cloud type usually forms in, and
suggests, good weather.
____ (4) Has a summit that lacks clear outline and isn’t clearly fibrous nor in the
shape of an anvil.
____ (5) Forms from the spreading out of CU or CB clouds.
____ (6) Forms by means other than the spreading out of CU .
____ (7) Is in a more or less continuous sheet or layer, or in ragged shreds, or is a
combination of both and bad weather isn’t present.
____ (8) Has a cirriform anvil.
____ (9) Often occurs below layers of AS and NS during bad weather.
(1) L2.
(2) L8
(3) L1
(4) L3
(5) L4
(6) L5
(7) L6
(8) L9
(9) L7
Column A Column B
____ (1) The greater part of this cloud type is semitransparent and the Sun or
Moon is dimly visible as though you’re viewing it through ground glass.
____ (2) Forms from the spreading out of CU or CB clouds.
____ (3) Is sufficiently dense to hide the Sun or Moon.
____ (4) This cloud type, the greater part of which is semitransparent, doesn’t
progressively invade the sky.
____ (5) Has two or more layers, is opaque in places, and doesn’t progressively
invade the sky.
____ (6) Is called a chaotic sky and occurs at several levels.
____ (7) Forms in patches and continually changes in appearance.
____ (8) Is arranged in bands or in one or more fairly continuous layers that
progressively invade the sky.
____ (9) Forms sproutings in the form of small towers or battlements.
a. M1.
b. M2.
c. M3.
d. M4.
e. M5.
f. M6.
g. M7.
h. M8.
i. M9.
(1) a.
(2) f.
(3) b.
(4) c.
(5) g.
(6) i.
(7) d.
(8) e.
(9) h.
Column A Column B
____ (1) Often called a “mackerel sky.”
____ (2) A dense cloud and is often in the shape of an anvil.
____ (3) Uniform in structure, covers the celestial dome, and may have a halo as the
only indication of its presence.
____ (4) Is in filaments, strands, or hooks that don’t progressively invade the sky.
____ (5) Progressively invades the sky and generally grows more dense, but the
continuous veil doesn’t reach 45º.
____ (6) Can have sproutings in the form of small turrets or battlements.
____ (7) Is in the form of hooks and/or filaments that progressively invade the sky
and become more dense.
____ (8) Progressively invades the sky and generally grows more dense. The
continuous veil extends to more than 45º.
____ (9) This cloud type isn’t progressively invading the sky and doesn’t
completely cover the celestial dome.
a. H1.
b. H2.
c. H3.
d. H4.
e. H5.
f. H6.
g. H7.
h. H8.
i. H9.
(1) i.
(2) c.
(3) g.
(4) a.
(5) e.
(6) b.
(7) d.
(8) f.
(9) h.
Why is it so important that weather personnel correctly identify orographically produced clouds
in the observation?
Because they’re important to flight operations due to the association of mountain-wave turbulence with
these types of clouds.
2. Supply the name and subtype number for each of the following orographic clouds:
(a) This middle-level orographic cloud type is observed in patches at one or more levels; the
elements are continually changing in appearance but generally remain stationary in spite of
high wind speeds.
(b) This orographic cloud type hugs the top of a mountain and gives the appearance of a
waterfall.
(c) This orographic cloud type is found on the leeward side of a mountain range and has vertical
development.
(a) Lenticular, M4.
(b) Foehn wall, L5.
(c) Rotor, L2.
What’s a layer?
Clouds or obscuring phenomena that have bases at the same approximate level. The layer may appear as
continuous cover or as detached elements. Also, both continuous and detached elements may combine to
form a layer.
Using the Reportable Contraction, Meaning, and Summation Amount of Layer table determine
the amount of sky coverage of a layer of CS that’s progressively invading the sky and whose
leading edge is 89º.
Four-eighths of sky cover.
If a layer was exactly between two reportable height values, which value would you report?
The lower of the two values.
What’s a ceiling?
The lowest broken or overcast layer aloft or the vertical visibility in a surface-based obscuring phenomena.
What are the two preferred methods used to obtain a layer height?
A ceilometer operating within its operational range and the known heights of unobscured portion of abrupt,
isolated objects within 11/2 nautical miles of the runway.
List at least five alternative methods used to obtain a layer height.
(1) Heights reported by a pilot.
(2) Based on the ascension rate of a ceiling balloon.
(3) Convective cloud height table.
(4) Based on the height of natural landmarks more than 11/2 miles from the airfield.
(5) Your own observational experience.
(6) Ceilometer indications that equal or exceed 10 times the baseline.
(7) Based on the size of the cloud elements.
(8) Reflection of city lights off of cloud bases.
From the following list of visibility markers, indicate those best suited for night markers with an
“N” and those best suited for day markers with a “D.” Add appropriate qualifying remarks after
“N” or “D” as applicable. (NOTE: Some markers may only be good under certain conditions.
Indicate under what conditions they might be poor. Also, indicate those makers that are only good
as guides to estimation of visibility.)
(a) A red light marker on a large building.
(b) A dark brown house.
(c) A line of trees.
(d) An airfield runway beacon light on an Air Force base.
(e) A white farmhouse and barn.
(f) Smokestack of a manufacturing plant.
(g) Red light on top of a TV tower.
(h) A church steeple.
(a) N (a good one).
(b) D (a good one).
(c) D (a good one).
(d) N (but only to estimate visibility).
(e) D (but is poor because of its color).
(f) D (a good one).
(g) N (a good one).
(h) D (a good one).
What’s the meaning of the term prevailing visibility?
The greatest distance known objects can be seen and identified throughout half or more of the horizon
circle surrounding the station.
When reporting sector visibility, how many compass points normally are used to identify sector
direction? What are they?
Eight. N, NE, E, SE, S, SW, W, NW.
What are the two requirements which must be met to report sector visibility?
(1) When sector visibility differs from prevailing visibility.
(2) When sector visibility is less than 3 miles.
When reporting sector visibility and more than one sector needs to be reported, how are the
sectors listed?
In a clockwise direction beginning with the northernmost sector.
Can you report the sector visibility if the sector visibility differs from prevailing visibility (but is
more than 3 miles)? Explain your answer.
Yes. If you consider it operationally significant.
What device is used to measure RVR?
Transmissometer.
What’s the RVR for the following report: R09/1600?
On runway 09, the RVR is 1600 meters.
Can you tell the exact RVR from the following report—R15/P6000FT? Explain.
No, it’s greater than 6000 feet but how much greater isn’t known. The maximum reportable value has been
exceeded.
What RVR is reported if the RVR is required to be reported but the equipment is inoperative?
RVRNO.
Name the two forms of liquid precipitation.
Rain and drizzle.
Define “freezing precipitation.”
Liquid precipitation that falls and freezes upon impact with objects on the ground or in flight.
____ (1) Transparent or translucent particles of ice that are round or irregular in shape.
They usually rebound when striking hard ground and make a sound on impact.
____ (2) Very small, white, opaque grains of ice, which usually fall in small quantities,
mostly from stratus clouds, and never as showers.
____ (3) Ice crystals that appear mostly branched in the form of six-pointed stars.
____ (4) Falls from strong convective clouds and occasionally freeze together, falling in
irregular lumps.
____ (5) Unbranched and in the form of needles, columns, or plates.
____ (6) Form exclusively in convective clouds and, under the right conditions, serve as
the nuclei for hail development.
a. Drizzle.
b. Ice pellets.
c. Snow pellets.
d. Hail.
e. Freezing rain.
f. Snow grains.
g. Ice crystals.
h. Snow.
(1) b.
(2) f.
(3) h.
(4) d.
(5) g.
(6) c.
What are the three categories of precipitation?
(1) Continuous.
(2) Intermittent.
(3) Showery.
What category of precipitation is usually associated with stratiform cloud types?
Continuous
What category of precipitation stops and starts at least once within the hour preceding the
observation.
Intermittent
What category of precipitation do swelling cumulus and cumulonimbus clouds produce?
Showery
What precipitation category changes intensity rapidly or begins and ends abruptly?
Showery
Column A Column B
____ (1) Individual raindrops aren’t identifiable.
____ (2) Snow is falling. There are no obstructions to vision present. The
prevailing visibility is ¼ mile.
____ (3) Ice pellets are falling and accumulating at the rate of 0.20 inch per
hour.
____ (4) Rain is falling. Scattered drops don’t completely wet an exposed
surface.
____ (5) Drizzle is falling and there are no obstructions to vision present. The
prevailing visibility is 1 mile.
a. Heavy snow.
b. Moderate snow.
c. Heavy rain.
d. Light rain.
e. Light drizzle.
f. Moderate drizzle.
g. Moderate ice pellets.
h. Light ice pellets.
(1) c.
(2) b.
(3) g.
(4) d.
(5) e.
What’s the unit of measure for liquid precipitation? How is a trace reported?
To the nearest 0.01 of an inch. Less than 0.005 of an inch.
Describe the process of measuring frozen precipitation.
Remove the collector-funnel unit and measuring tube. Pour a measured amount of water into the overflow can to melt the solid precipitation, pour the melted liquid into the measuring tube, measure the total amount of liquid, and subtract the amount of warm water used.
What’s the term for a whirling vortex which doesn’t reach the ground?
Funnel cloud.
What’s the term for a whirling vortex which descends to the surface over water.
Waterspout.
What’s the term for a whirling vortex which touches the ground?
Tornado.
What distinguishing feature do funnel clouds, water spouts, and tornados have in common?
A funnel-shaped appendage hanging from the base of the cloud.
What criteria must be met for tornadic activity to be classified as occurring “at the station?”
The phenomenon must be visible from the observation site.
When can a thunderstorm be included in an observation even if thunder isn’t heard?
When hail is falling or lightning is observed in the immediate vicinity of your station and the local noise
level prevents you from hearing the thunder.
When does a thunderstorm end?
15 minutes after the last occurrence of thunder, hail, or lightning.
List the four hydrometeors.
(1) Fog.
(2) Blowing snow.
(3) Freezing fog.
(4) Blowing spray.
List the four lithometeors.
(1) Dust.
(2) Sand.
(3) Haze.
(4) Smoke.
Classify the specific hydrometeor or lithometeor described in each of the following statements:
(a) Small water droplets suspended in the air.
(b) Reported only at sea stations near large bodies of water.
(c) Finely divided earthly matter uniformly distributed in the atmosphere.
(d) Loose sand blown by the wind and restricting visibility to 4,800 meters.
(e) A uniform veil that subdues natural colors.
(f) The disk of the sun appears very red at sunrise and the visibility is 8,000 meters due to a
suspension of particles in the air.
(a) Fog.
(b) Blowing spray.
(c) Dust.
(d) Blowing sand.
(e) Haze.
(f) Smoke.