CTS - Aviation Weather Theory
Supercooled water droplets are abundant in clouds at temperatures from:
0° to -15° C
You should avoid any thunderstorm identified as severe by at least:
20 nautical miles.
The Surface Analysis Chart depicts which of the following?
Actual frontal positions, pressure patterns, temperature, dew point, wind, weather, and obstructions to vision at the valid time of the chart.
Interpret the following PIREP. MRB UA/OV MRB/TM1430/FL060/TPC182/SK BKN BL/WX RA/TB MDT.
At 6,000 feet; between layers; moderate turbulence; rain.
Which is most related to the intensity of precipitation?
Cloud thickness.
Which changes of state of moisture absorb heat energy?
Evaporation and melting.
A prognostic chart depicts the conditions:
Forecast to exist at a specific time in the future.
While flying a 3° glide slope, a constant tailwind shears to a calm wind. Which conditions should the pilot expect? Indicated airspeed and pitch attitude:
Increase and there is a tendency to go above glide slope.
An increase in temperature with altitude is known as an:
Inverted lapse rate.
Most clouds are formed because the air:
Is cooled.
Which combination would result in the lowest true altitude, assuming the altimeter setting remains constant?
Low pressure and low temperature.
Which condition would cause the true altitude of the aircraft to be lower than the indicated altitude, even if the altimeter is accurate?
Temperature colder than standard.
If using airborne radar and flying in the vicinity of thunderstorms, what is a good procedure?
Tilt the antenna up and down occasionally.
SIGMETs are issued as a warning of weather conditions that are potentially hazardous:
To all aircraft.
Which values are used for winds aloft forecasts?
True direction and knots.
At which temperature range would you expect to encounter the heaviest icing in cumuliform clouds?
0° to -15° C.
In the lower layers of the atmosphere, pressure decreases with an increase in altitude at a rate of approximately:
1 inch per 1,000 feet.
How long does it normally take radiation or ground fog to burn off?
1 to 3 hours.
With a surface temperature of 28 °C and a surface dew point of 23 °C, what would you estimate the base of the clouds to be?
2,000 feet.
During the cumulus (growth) stage of a thunderstorm, the growth rate of a cloud may exceed:
3,000 feet per minute.
Moving up in the atmosphere, unsaturated air gets cooler at approximately what rate (dry adiabatic lapse rate)?
3°C per 1,000 feet.
If the air temperature is +8°C at an elevation of 1,350 feet MSL and a standard (average) temperature lapse rate exists, what will be the approximate freezing level?
5,350 feet MSL.
A jet stream is defined as wind of:
50 knots or greater.
What is the wind shear forecast in the following TAF?
500 feet AGL from 270° at 50 KT.
The station originating the following weather report has a field elevation of 1,300 feet MSL. From the bottom of the overcast cloud layer, what is the overall thickness? (tops of OVC are reported at 3800 feet MSL): SPECI KOKC 2228Z 28024G36KT 3/4SM BKN008 OVC020 28/23 A3000.
500 feet.
What is the maximum forecast period for AIRMETs?
6 hours.
Maximum downdrafts in a microburst encounter may be as strong as:
6,000 feet per minute.
Which response most closely interprets the following PIREP? UA/OV OKC 063064/TM 1522/FL080/TP BE1900/TA M04/WV 245040/TB LGT/RM IN CLR
64 nautical miles on the 63° radial from Oklahoma City VOR at 1522 UTC, flight level 8,000 ft. Type of aircraft is a Beech 1900.
An aircraft that encounters a headwind of 45 knots, within a microburst, may expect a total shear across the microburst of:
90 knots.
An accumulation of frost on the airfoil surface could cause which of the following?
A 5% to 10% increase in stall speed for airplanes and a loss of lift for helicopters.
The standard temperature lapse rate in the lower layers of the atmosphere is:
A decrease of 2° C per 1,000'.
The zone between two air masses of different properties is called:
A front.
If, while in flight, an area of severe turbulence is encountered, which flight condition should you attempt to maintain?
A level flight attitude.
When a climb or descent through an inversion or wind-shear zone is being performed, the pilot should be alert for which of the following change in aircraft performance?
A sudden change in airspeed.
Which two types of fog could form even though the skies are cloudy?
Advection and upslope fog.
Which types of fog must have a wind in order to form?
Advection and upslope fog.
Which type of fog usually forms along coastal areas in the winter?
Advection fog.
Ice forming on the static ports would cause which of the following instruments to be unreliable?
Airspeed indicator, altimeter, and VSI.
If during flight, rough air or severe turbulence is encountered:
Airspeed should be reduced to maneuvering speed or less.
Which of the following are forms of precipitation?
All of the answers are correct.
Which of the following is a factor regarding the type of weather found in a front?
All of the answers are correct.
Which of these conditions might produce fog?
All of the answers are correct.
Wind shear may exist:
All of the answers are correct.
Which of the following clouds are classified in the "low" family of clouds?
All of the listed clouds are in the low family of clouds.
Which of the following clouds are part of the "high" cloud family?
All of the listed clouds.
Wind shear associated with a low level temperature inversion can cause an aircraft to stall. How should you alleviate this danger?
Allow a margin of airspeed above normal approach speed.
Which of the following clouds are part of the "middle" cloud family?
Altocumulus.
Standard Atmosphere was created by:
Averaging conditions to create an idealized atmosphere.
An air mass that moves out of its source region will:
Become modified taking on characteristics of the surface below.
Which type of icing is hard, heavy, tenacious, and most difficult to break off with deicing equipment?
Clear.
If flying in IFR conditions and you encounter freezing rain beneath the frontal slope, what is the best procedure to avoid icing?
Climb to an altitude above the frontal slope where you will encounter above freezing temperatures.
The normal circulation around a high pressure area at the surface in the northern hemisphere is:
Clockwise and crossing the isobars at a 30° angle.
What type clouds can be expected when an unstable air mass is forced to ascend a mountain slope?
Clouds with extensive vertical development.
Which areas would be most conducive to the formation of fog?
Coastal areas and industrial areas.
Microscopic particles of salt, dust, and combustion byproducts are necessary for water vapor molecules to change state from gas to liquid or solid. These are called:
Condensation nuclei.
An air mass passing over a warmer surface results in the formation of what?
Convective currents.
On a warm day when flying at a lower altitude, a pilot might experience turbulence associated with ____________ as they transition from flight over a field with a crop growing to flight over a plowed field.
Convective currents.
When air is lifted it:
Cools due to decreasing pressure.
In the northern hemisphere which of the following forces causes winds to apparently turn to the right?
Coriolis force.
During a hot summer afternoon along coastal areas, which will most likely form along the shoreline?
Cumuliform clouds.
Which type of clouds are most likely to form when there is a rapid decrease in temperature with an increase in altitude?
Cumuliform.
Which of the following clouds would probably contain the worst turbulence?
Cumulonimbus.
What are the three stages of a thunderstorm cell during its life cycle?
Cumulus, mature, and dissipating.
The temperature to which the air must be cooled to become saturated by the water vapor already present in the air is known as the:
Dew point.
Which of the following characterizes the dissipating stage of the thunderstorm cell?
Downdrafts.
Although fog may form during any season it occurs most frequently:
During colder months.
When a high pressure stagnates over an industrial area, during which time of the day would you expect the lowest visibility?
Early morning.
One of the greatest hazards of thunderstorms is hail, which is a hazard:
Even miles away from the storm cloud.
True or false? If you encounter a cumulonimbus cloud that doesn't appear to be producing rain, hail, or lightning, it is safe to pass nearby.
False.
When is the temperature at one of the forecast altitudes omitted at a specific location or station in the Winds and Temperatures Aloft Forecast (FD)?
For the 3,000-foot altitude (level) or when the level is within 2,500 feet of station elevation.
Which condition is most favorable for rapid accumulation of clear ice?
Freezing rain below a frontal surface.
Which of the following forces tends to slow the wind speed?
Friction.
A common type of ground or surface based temperature inversion is that which is produced by:
Ground radiation on clear, cool nights when the wind is light.
Which family of clouds is least likely to contribute to structural icing on an aircraft?
High clouds.
Although it is not a hard and fast rule, which of the following conditions would most likely produce the most favorable flying conditions?
High pressure.
What are the four families of clouds?
High, middle, low, and those with extensive vertical development.
Which type of fog is formed by the process of desublimation?
Ice fog.
A temperature inversion will normally form only:
In stable air.
The Weather Depiction Chart is issued how often and is a valuable source of what information?
Issued every 3 hours and depicts areas of IFR, VFR, and MVFR category conditions.
What information is provided by a Convective Outlook (AC)?
It provides prospects of both general and severe thunderstorm activity during the following 24 hours.
Which condition would be most likely for the formation of rime ice?
Light drizzle or stratus clouds.
A pilot reporting turbulence that momentarily causes slight, erratic changes in altitude and/or attitude should report it as:
Light turbulence.
A low level stable air mass is associated with what sorts of clouds?
Low stratus and fog.
A ceiling is defined as the height of the:
Lowest layer of clouds or obscuring phenomena aloft that is reported as broken or overcast.
A front is defined as stationary if:
Neither air mass is replacing the other.
The earth's atmosphere is primarily composed of:
Nitrogen.
What conclusion(s) can be drawn from a Constant Pressure Chart?
Observed temperature, wind, and temperature/dewpoint spread along the proposed route can be approximated.
What is the primary difference between a ceiling caused by an obstruction to vision and one caused by clouds?
Obstructions to vision are based on the surface whereas clouds are based aloft.
Which is the most likely time for on-shore and off-shore thunderstorms to form?
Off-shore at night and on-shore during the afternoon.
Wind shear associated with a thunderstorm is commonly found where? Choose the most complete answer.
On all sides of the thunderstorm cell and directly under the cell.
What characteristics are observed when a headwind shears to be a constant tailwind?
PITCH ATTITUDE: Decreases; REQUIRED THRUST: Increased, then reduced; VERTICAL SPEED: Increases; IAS: Decreases, then increases to approach speed.
What is the best source for determining the location and intensity of actual icing conditions?
Pilot reports.
A pilot planning to depart at 1100Z on an IFR flight is particularly concerned about the hazard of icing. What sources reflect the most accurate information on icing conditions (current and forecast) at the time of departure?
Pilot weather reports (PIREPs), AIRMETs, and SIGMETs.
What is an indication that a thunderstorm cell has reached the mature stage?
Precipitation begins to fall from the cloud base.
Which type of fog is formed by the evaporation process?
Precipitation-induced fog.
The rapid and drastic changes in ___________ associated with a passing thunderstorm can cause the altimeter to be more than 100 feet in error.
Pressure.
On which chart(s) would you find information on lines and cells of hazardous thunderstorms?
Radar Summary Chart.
A clear sky, a light wind, and high relative humidity are conditions which aid the formation of:
Radiation fog.
What is meant by the entry in the remarks section of METAR surface report for KBNA? METAR KBNA 211250Z 33018KT 290V260 1/2SM R31/2700FT +SN BLSNFG VV008 00/M03 A2991 RMK RAE42SNB42
Rain ended 42 past the hour, snow began 42 past the hour.
Which of the following terms describes the amount of water vapor present compared to the total water vapor possible at a given temperature and is given as a percentage?
Relative humidity.
Which is prevalent with cold frontal or squall line thunderstorms and signifies an extremely turbulent zone?
Roll cloud.
Which type of clouds are associated with a mountain wave?
Rotor clouds and altocumulus standing lenticular clouds.
Moist air moving over a warm surface and heated from below will generally result in:
Rough flying conditions and increasing possibility of showers.
What is the expected duration of an individual microburst?
Seldom longer than 15 minutes from the time the burst strikes the ground until dissipation.
Which of the following determines the severity of icing?
Size of the water droplets and temperature.
Frontal Waves normally form on:
Slow moving cold front or stationary front.
Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high?
Smooth air and poor visibility due to fog, haze, or low clouds.
A narrow band of intense thunderstorms which may form in front of a fast moving cold front is called a:
Squall line.
A non-frontal narrow band of active thunderstorms which presents the single most intense weather hazard to aircraft is known as a:
Squall line.
Restricted visibility at or near the surface over large areas usually indicates:
Stable air.
Which type of thunderstorm tends to form with frontal weather systems?
Steady state thunderstorms.
What type of fog tends to form when air is blowing from a cold surface over warmer water?
Steam fog.
What type of clouds will be formed if very stable moist air is forced up slope?
Stratified clouds with little vertical development.
Which type of clouds are most likely to form in moist stable air?
Stratiform.
Spacing between isobars on a weather chart can give the pilot a general indication of the:
Strength of the wind.
What conditions are necessary for a thunderstorm to form?
Sufficient water vapor, an unstable lapse rate, and a lifting force.
An air mass is a large body of air that has fairly uniform ________________________ characteristics.
Temperature and moisture.
Which condition would most likely produce fog?
Temperature-dew point spread is 5 °F (2.8 °C) and decreasing.
Identifying an air mass as tropical or polar is in relation to its:
Temperature.
Around what temperatures would the heaviest icing most probably be found in a thick nimbostratus cloud?
Temperatures at or slightly below freezing.
What are the two conditions necessary for structural icing to form in flight?
Temperatures freezing or below and visible liquid moisture.
Which condition would result in the air becoming unstable? The temperature of:
The air which was lifted is warmer than the surrounding air temperature.
Clear air turbulence is strongest on what side of a jet stream?
The cold side
Which of these best describes a cold front?
The leading edge of an advancing cold air mass.
Which is the best indication as to the intensity of a thunderstorm?
The more frequent the lightning, the more intense the storm.
Compare the rate of cooling when saturated air is lifted to the rate of cooling when unsaturated air is lifted.
The rate of cooling in saturated air is slower.
What determines the structure or type of clouds which form as a result of air being forced to ascend?
The stability of the air before lifting occurs.
Which cloud belongs to the family of "vertically developed" clouds?
Towering cumulus.
Which of the following layers of the atmosphere extends from the surface to an altitude of about 20,000' over the poles and 48,000' over the equatorial regions?
Troposphere.
Standing lenticular clouds, in mountainous areas, typically indicate which of the following conditions?
Turbulence.
Which is a good procedure if you are flying near a thunderstorm at night?
Turn the instrument lights to high intensity.
Which of the following has the greatest effect in creating pressure differences?
Unequal heating of air.
When are severe weather watch bulletins (WW) issued?
Unscheduled and issued as required.
Which of the following combinations of weather producing variables would likely result in cumuliform-type clouds, good visibility, rain showers, and possible clear-type icing in clouds?
Unstable, moist air, and orographic lifting.
If you must climb through a layer of icing, which is the best procedure?
Use an airspeed a little faster than normal climb speed.
A thunderstorm cloud which displays rounded, irregular pockets or festoons from its base is called "cumulonimbus mammatus". This type of cloud is a signpost of:
Violent turbulence.
Clouds, fog, or dew will always form when:
Water vapor condenses.
Which of the following properties always changes across a front?
Wind
Which range of wind speed tends to deepen a radiation fog formation?
Wind up to 5 knots.
What is a characteristic of low-level wind shear as it relates to frontal activity?
With a warm front, the most critical period is before the front passes the airport.
Where does wind shear occur?
With either a wind shift or a wind speed gradient at any level in the atmosphere.
When does an occluded front produce the most dangerous forms of weather?
With warm front occlusion that pushes unstable air aloft.
