Wx Theory + Wx Services

Question 1

What happens when warm, moist, stable air flows upslope

Answer 1

It produces stratus type clouds

Question 2

What type of cloud is forecast in a TAF?

Answer 2

The only type of cloud forecast in TAF reports is cumulonimbus clouds. Also known as thunder clouds, it’s the only type of cloud that can produce hail, thunder, or lightning.

Question 3

Which inflight advisory would contain information on severe icing not associated with thunderstorms?

Answer 3

SIGMET

Question 4

What are two ways to determine PA?

Answer 4

Pressure altitude is read by setting altimeter to 29.92 and reading the kollsman window, or calculating manually by: subtract current altimeter setting from 29.92, multiply by 1000, add to field elevation (subtract if negative)

Question 5

Why is DA useful? How do you calculate it?

Answer 5

Density altitude is used to estimate airplane performance. Found with E6B or DA chart. On a DA chart, enter at the bottom with OAT, draw a line straight up until you reach the correct PA. Go direct left to find DA.

Question 6

What are the types of weather briefs from FSS?

Answer 6

Standard - within 2 hrs of flight

Outlook briefing - When requesting weather information for the following morning, or more than 6 hrs until departure

Abbreviated briefing - just to confirm info

Question 7

What is a graphical forecast for aviation (GFA) used for?

Answer 7

To best determine general forecast weather conditions covering a flight information region

Question 8

What situation is most conducive to the formation of radiation fog?

Answer 8

Warm, moist air over low, flatland areas on clear, calm nights.

Question 9

If an unstable air mass is forced upward, what type of clouds can be expected?

Answer 9

Clouds with considerable vertical development and associated turbulence.

Question 10

What should you do if you encounter severe turbulence?

Answer 10

Upon encountering severe turbulence, the pilot should attempt to maintain a level flight attitude.

Question 11

What is the relationship between weather and heat exchange?

Answer 11

Every physical process of weather is accompanied by or is a result of a heat exchange

Question 12

What affects the amount of water vapor that air can hold?

Answer 12

The amount of water vapor which the air can hold depends on air temperature

Question 13

What is ATIS

Answer 13

ATIS is the continuous broadcast of recorded information concerning non-control information in selected high activity terminal areas

Question 14

What’s the effect of warming from below, upon the stability of the airmass

Answer 14

Warming from below would decrease the stability of an air mass.

Question 15

Explain NOTAM

Answer 15

NOTAM - notice to air mission. NOTAMs contain aeronautical information that could affect the decision to make a flight.

Question 16

What is necessary for the formation of fog?

Answer 16

a small temp-dew point spread

Question 17

What is associated with steam fog?

Answer 17

Steam fog is associated with hazardous low-level turbulence & icing

Question 18

Describe the formation of thunderstorms

Answer 18

For a thunderstorm to form, the air must have sufficient water vapor, an unstable lapse rate, an initial upward boost (lifting) to start the storm process in motion. Lifting can be provided by surface heating, converging winds, sloping terrain, a frontal surface, or any combination of these. A thunderstorm cell progresses through three stages during its life cycle: cumulus stage (3-5 mile height), mature stage (5-10 mile height), dissipating stage (5-7 mile height). Although not all cumulus clouds form into thunderstorms, all thunderstorms begin as cumulus clouds.

Air mass thunderstorms last for an hour or two. Steady-state thunderstorms are associated with weather systems, often form into squall lines.

Question 19

How are clouds categorized?

Answer 19

Clouds are divided into four families according to their height range.

Question 20

What happens when the relative humidity is high beneath a low-level temperature inversion layer?

Answer 20

The weather conditions that can be expected include smooth air and poor visibility due to fog, haze, or low clouds.

Question 21

How do you read winds aloft forecast when winds are forecast above 99 kts?

Answer 21

Winds aloft - if wind speed is forecast to be 100 kts - 199 kts, they will add 50º to the direction and subtract 100 from the speed.

Question 22

What is indicated by a current convective SIGMET?

Answer 22

Thunderstorms obscured by massive cloud layers.

Question 23

A pilot can expect a wind shear zone in what temperature inversion conditions?

Answer 23

A pilot can expect a wind shear zone in a temperature inversion whenever the windspeed at 2000 to 4000 ft above the surface is at least 25 kts.

Question 24

What conditions are favorable for clear ice accumulation?

Answer 24

freezing rain below a frontal surface.

Question 25

When telephoning flight service for preflight weather information pilots should state: (11 items)

Answer 25

ID themselves as pilots, VFR or IFR, aircraft ID or pilots name, aircraft type, departure point, route of flight, destination, altitude, estimated time of departure, estimated time en route or time of arrival.

Question 26

Which conditions result in the formation of frost?

Answer 26

The temperature of the collecting surface is at or below the dew point of the adjacent air and the dew point is below freezing.

Question 27

What is a characteristic of stable air?

Answer 27

Stratiform clouds. (since stable air resists convection, clouds in stable air form in horizontal, sheet-like layers or “strata”)

Question 28

Two conditions are necessary for structural icing in flight:

A condition favorable for structural icing is freezing _____

Answer 28

the a/c must be flying through visible water such as rain or cloud droplets, and the temperature at the point where the moisture strikes the a/c must be 0º or colder.

A condition favorable for structural icing is freezing rain.

Question 29

Characteristics of an unstable air mass include ___ clouds, showery ___, rough ____, and good ___

Answer 29

cumuliform clouds, showery precipitation, rough air (turbulence), and good visibility (except in blowing obstructions)

Question 30

Possible mountain wave turbulence could be anticipated when winds of __ knots or greater blow across a mountain ridge, and the air is stable/unstable.

Answer 30

40
STABLE

Question 31

Absence of the sky condition and visibility on an ATIS broadcast indicates that the ceiling is at least ___ ft and the visibility is _ miles or more.

Answer 31

5000
5

Question 32

When the term “light and variable” is used in terms of a winds aloft forecast, the coded group and wind speed is “____” and less than _ knots

Answer 32

9900
5 kts

Question 33

Dew point is the temperature to which air must be cooled to

Answer 33

Become saturated by the water vapor already present in the air

Question 34

Clouds, fog, or dew will always form when

Answer 34

water vapor condenses

Question 35

Pressure altitude is equal to true altitude under____

Answer 35

Standard atmospheric conditions

Question 36

How to read a METAR, common phraseology

A02
LTG DSNT ALQDS
RAB19
TSB23
P0000
P0005
T02830228
T12831228
SLP114
10194
20178
LTGICCG
OHD
LTGICCCCG
DISPTD
GR
BR

METAR is observation, within 5 miles. 4 types

Answer 36

A02 precipitation discriminator
LTG DSNT ALQDS - lightning distant all quadrants
RAB19 rain begins 19 min after hour
TSB23 thunderstorm begins 23 min after hour
P0000 precipitation in inches
P0005 = ½ inch rain precipitation
T02830228: temp 28.3ºC, dew point 22.8ºC
T12831228: temp -28.3ºC, dew point -22.8ºC (“1” means negative)
SLP114 = 1011.4 mB
10194 = max temp in last 6 hours 19.4ºC
20178 = minimum temp in last 6 hours 17.8ºC
LTGICCG = lightning inside cloud, cloud to ground
OHD = overhead
LTGICCCCG = lightning inside cloud, cloud to cloud, cloud to ground
DISPTD = dissipated
GR - hail
BR - mist

METAR is observation, within 5 miles. 4 types
From
Temporary
Probability
Becoming

Question 37

What is a TAF?

PROB40
TX 20/1819Z
TN 10/1910Z
P6SM

Answer 37

TAF, what is it? - Terminal Aerodrome Forecast. Usually issued at larger airports, encompasses a 5 statue mile radius, valid for 24 or 30 hrs, updated at 0000Z, 0600Z, 1200Z, 1800Z

“PROB40” probability of 40%. Only 30% or 40% probability on TAFs
TX 20/1819Z = max temp 20º on day 18 @ 1900Z
TN 10/1910Z = min temp 10º on day 19 @ 1000Z
P6SM ≥6 miles visibility

Question 38

Types of AWOS reports

Answer 38

There are nine types of AWOS reports. AWOS stations are managed by the FAA. ASOS stations are managed by the National Weather Service and play a critical role in the NWS’s climatological database. ASOS stations are more advanced than AWOS and are used in generating forecasts (like TAFs).

Question 39

Standard sea level pressure

Answer 39

1013.2 millibars

Question 40

What are the types of icing? When is icing most likely

Answer 40

Clear - solid/dense/clear ice, occurs more slowly. Water droplets hit surface and freeze more slowly than rime.

Rime - occurs in cooler temperatures when water droplets hit aircraft surface and rapidly freeze, trapping air bubbles in the mix.

Mixed - Clear + Rime ice

Icing most likely when flying into visible moisture near/at/below freezing. If you encounter icing, fly faster than normal, DO NOT USE FLAPS, immediately maneuver to area of more favorable conditions (180º turn or turn towards warm area/sun light). Do not be afraid to declare emergency or ask ATC for help, find out where closest airport is. Stall speed will increase and horizontal stab can accumulate ice which would make the a/c much less maneuverable. It would be wise to immediately land.

Question 41

Atmosphere goes up xxx miles. Four distinct layers, A, B, C, D. In the A, the standard lapse rate is 2ºC/1,000’. Pressure decreases by 1” Hg/1,000’ altitude gain. Above the A is the _____pause, a boundary layer that borders the B. _____pause: traps moisture and associated weather in the A. The _____pause is associated with the jet stream and possible clear ice turbulence. Location of the _____pause varies with latitude and season, and therefore has an elliptical shape not round.

Answer 41

Atmosphere goes up 350 miles. Four distinct layers, troposphere, stratosphere, mesosphere, thermosphere. In the troposphere, the standard lapse rate is 2ºC/1,000’. Pressure decreases by 1” Hg/1,000’ altitude gain. Above the troposphere is the tropopause, a boundary layer that borders the stratosphere. Tropopause: traps moisture and associated weather in the troposphere. The tropopause is associated with the jet stream and possible clear ice turbulence. Location of the tropopause varies with latitude and season, and therefore has an elliptical shape not round.

Question 42

Uneven heating of the earth’s surface upsets the equilibrium of the atmosphere. This creates changes in ___ movement and __________ pressure. The movement of the air around the earth’s surface is called atmospheric _______.

Answer 42

Uneven heating of the earth’s surface upsets the equilibrium of the atmosphere. This creates changes in air movement and atmospheric pressure. The movement of the air around the earth’s surface is called atmospheric circulation.

Question 43

Coriolis force - The apparent ______ of moving objects with relation to a reference point, the earth. Causes moving objects, such as water or air to curve to the right/left In the northern hemisphere. And causes them to curve to the right/left in the southern hemisphere. Caused by rotation of the earth.

Answer 43

Coriolis force - The apparent deflection of moving objects with relation to a reference point, the earth. Causes moving objects, such as water or air to curve to the right In the northern hemisphere. And causes them to curve to the left in the southern hemisphere. Caused by rotation of the earth.

Question 44

Air flows from areas of ____ to ___ pressure b/c air always seeks out areas of ___ pressure.

Answer 44

Air flows from areas of high to low pressure b/c air always seeks out areas of low pressure.

Question 45

In the N.H. (northern hemi.) air flows in a clockwise/counterclockwise (anticyclonic) motion around areas of high pressure, and away from the high P. Air flows in a clockwise/counterclockwise (cyclonic) motion around areas of low pressure, and into the low P. Air flow into low P areas brings _____ and precipitation. This is why bad weather is commonly associated with areas of low P. On a flight from west to east, favorable tailwinds would be found on the northern side of a high P area, or on the southern side of an area with low P.

Answer 45

In the N.H. (northern hemi.) air flows in a clockwise (anticyclonic) motion around areas of high pressure, and away from the high P. Air flows in a counterclockwise (cyclonic) motion around areas of low pressure, and into the low P. Air flow into low P areas brings cloudiness and precipitation. This is why bad weather is commonly associated with areas of low P. On a flight from west to east, favorable tailwinds would be found on the northern side of a high P area, or on the southern side of an area with low P.