Weather Flashcards
(221 cards)
1
Q
Justify your go/no-go decision. In other words, I want you to walk me through all the weather charts that you used during your planning for this VFR cross-country flight and prove to me that you won’t encounter any adverse weather. If there is adverse weather and you’re making a go decision, show me that you’ve competently planned around it.
A
Typical charts that applicants use: Radar Summary, Surface Analysis, Convective Outlook, Low Level Significant Weather Prognostic, Winds Aloft, METARs and TAFs of all stations along the flight route, Graphical Area Forecast charts for the flight full duration and range of altitudes, PIREPs, various icing and freezing level charts
2
Q
Provided the weather is unavoidable, what kind of weather would cause you to make a no-go decision for this VFR flight?
A
Thunderstorms or any other convective activity, high winds (including windshear), excessive turbulence, low cloud ceilings/visibility, icing conditions, and heavy precipitation.
3
Q
Take me through the weather charts and sources that you used to verify that we won’t encounter any such weather (note: there are many options/answers here)
A
● Thunderstorms/convection: Radar Summary, Graphical Area Forecast, METAR/TAF,
PIREP, Convective Outlook, Convective SIGMET.
● High winds: Winds Aloft, Surface Analysis, METAR/TAF, Graphical Area Forecast,
AIRMET/SIGMET.
● Turbulence: AIRMET/SIGMET/Convective SIGMET, Graphical Area Forecast, Low
Level Prog.
● IMC: Graphical Area Forecast, METAR/TAF, Low Level Prog.
● Low cloud ceiling: Graphical Area Forecast, METAR/TAF.
● Potential icing: Winds Aloft and/or Freezing Level charts to determine freezing level;
Graphical Area Forecast and METAR/TAF to determine location of visible moisture.
● Heavy precip: Radar Summary, METAR/TAF, Graphical Area Forecast
4
Q
How do you determine cloud coverage and visibility beyond the 5 sm range of a TAF?
A
Use the GFA tool
5
Q
What are the three types of weather products?
A
Observation, forecast, and analysis
6
Q
When is the Radar Summary (Radar Coded Message) chart issued, and what is its valid
time?
A
Issued every 30 minutes, 15 and 45 minutes past the hour (used to be issued
hourly).
It’s an observation, so it’s valid at the time observed, i.e. the time stated on the
chart: 04/26/2015 at 2315Z.
7
Q
What type of equipment generates radar observations of weather in the U.S.?
How does this radar work?
A
Doppler radars, i.e.
NEXRAD (Next Generation Weather Radar).
It sends out a signal that reflects (or echoes) off of precipitation. The radar then measures the reflective power in terms of decibels (dBZ). The higher the reflectivity, the more intense the precipitation
8
Q
Would you expect to encounter the strongest precipitation in the green or pink regions?
A
Pink, those represent the highest decibels
9
Q
What information does this chart provide?
A
Location of precipitation, precipitation intensity, qprecipitation echo tops, cell movement speed and direction
10
Q
Are echo tops the same as cloud tops?
A
No, echo tops represent the highest altitude containing precipitation. Cloud tops are generally slightly above this
11
Q
Nevada is all white . . . does this mean that there are no clouds in Nevada?
A
No, this chart does not show cloud coverage; it shows precipitation. The colored areas will certainly have
clouds, as precipitation needs to fall from something, but just because there is no
precipitation depicted doesn’t mean there are no clouds
12
Q
Name some limitations associated with radar-generated weather products?
A
● Beam overshoot/undershoot: some of the Doppler radars that generate this image are
on mountain tops, and the radars don’t look down . . . so any precipitation occurring
below the elevation of the radar equipment won’t be detected.
● Beam blockage: terrain can block the radar beam.
● Ground clutter: echo returns from trees, buildings, or other objects on the ground are usually automatically removed from the image. Usually.
● Anomalous propagation (AP): a pattern of ground echoes caused by super-refraction of the radar beam. Super-refraction causes the radar beam to bend downward and strike the ground.
● Ghosts: echoes in apparently clear air caused by a “cloud” of point targets.
● Angels: echoes caused by a physical phenomenon not discernible by the eye at the radar site, such as bats, birds, or insects.
● Other non-meteorological phenomena: E.g. wind farms, or smoke from forest fires.
13
Q
What are some additional limitations associated specifically with the Radar Summary Chart?
A
AC00-45H says that tops above 50,000ft can be disregarded, as they are likely a
mistake. Also, this chart is merely a snapshot of the weather at a specific time - weather changes rapidly, so this chart should be considered highly supplemental to any preflight weather briefing.
14
Q
What’s a major concern about flying through a region showing high echo tops?
A
Stronger updrafts, possibly leading to more severe convective activity.
15
Q
How often is the Wind and Temperature Aloft Forecast (FB) issued, and when is it valid?
A
The forecast is now produced 4 times/day (PHAK wrongly still says twice daily). The wind and temperature information depicted in the forecast are predicted to occur at the valid time specified in the header; however, the information CAN BE USED for flights occurring within
the specified “for use” time range.
16
Q
Are the wind directions true or magnetic?
A
true
17
Q
What does 9900 mean?
A
Light and variable.
18
Q
Why are wind and temperature not listed for SIY at 3000ft?
A
Wind is not listed within 1,500 ft of a location’s elevation. Temperatures are only provided for the 6,000 ft level and above.
Use the METAR/TAF to interpolate winds and temps at altitudes near field elevation.
Surface friction makes the wind predictions difficult.
19
Q
Why is no temperature listed for BIH at 6,000 ft?
A
Temperatures are not listed within 2,500 ft
of a location’s elevation (and again, never for the 3,000 ft elevation).
20
Q
What wind and temperature would you expect in the vicinity of the FOT station at 34,000ft? 820547
A
wind from 320 at 105 kts, temperature -47 degrees C
21
Q
What tells you that the temperature is negative?
A
The header states that all temps
above FL240 are negative.
22
Q
Would you expect stable or unstable air flying in SEA below 12,000ft? Why?
3000’ 2510
6000’ 2411-01
9000’ 2410 -5
1200’ 1913 -9
A
Stable.
Temperature drops of 2 degrees or fewer for every 1,000 ft of increased altitude are generally indicative of stable air. In the case of SEA, the temperature drops by only 8 degrees between 6,000 and 12,000 ft. Also noteworthy, the wind velocities are not significant
23
Q
What is the freezing level along your route of flight?
A
(Interpolate the altitude with a 0
degree temperature.)
24
Q
What are the issue and valid times for the Surface Analysis Chart?
A
This chart is issued every 3 hours, once analysis of the observed weather is complete. The valid times are either 00, 03, 06, 09, 12, 15, 18, or 21 UTC. In the case of the chart above, the weather shown on the chart is valid for 2100Z.
25
What do the maroon solid lines represent?
Isobars. These connect areas of equal sea
level pressure.
26
So if the pressure reads “1014”, say, that does not indicate station pressure?
Correct, it’s station pressure adjusted down to sea level.
27
What kind of weather would you expect to encounter in areas where the bars are close together?
Why?
High winds.
Isobars close together represent a steep pressure gradient. This causes the air to be more inclined to move.
28
What does the orange scalloped line extending up from Mexico continuing through the middle of the U.S. represent?
What’s a dry line:
Dry line.
During parts of the year, moist air comes up from the Gulf of Mexico.
The result is that moist air blankets the eastern U.S., whereas dry air remains dominant in the southwest. The dividing line is known as the dry line
29
What does the dashed orange line extending up from Florida along the east coast represent?
What’s a trough, and what kind of weather would you expect to encounter flying along
one?
A trough
It’s an elongated area of relatively low pressure. Expect generally poor weather,
as low-pressure systems involve updrafts, which are conducive to convective activity
30
The station plot in south western California is a blue circle surrounded by another blue
circle. What does this symbol indicate?
Wind calm
31
Surrounding the light-and-variable symbol, what do the red “81,” green “42,” orange “137,” and orange “\” with a “-7” to the right of it, all represent?
Temperature 81 degrees F, dewpoint 42 degrees F, pressure 1013.7 mb, pressure continuously fell over the previous 3
hours by .7 mb.
32
What does an “M” inside a station plot circle indicate?
Missing cloud observation
33
In northern Georgia there is a pink “R” just to the left of the high pressure system. What does this symbol indicate?
Thunderstorm.
34
What kind of chart is a Low Level Significant Weather Prognostic?
Forecast
35
What kind of weather is depicted on this chart?
(Just read from the legend on the bottom of the chart.) IFR, MVFR, moderate or greater turbulence, freezing levels.
36
What are the issues and valid times for this chart?
Issued 4 times/day, valid at the specific
times listed on the charts. The left and right panels will always be 12 hours apart
37
On the left panel, what does the “/” after the “150” in Idaho mean?
The symbol means down to the surface. So the moderate turbulence descends from 15,000 ft MSL down to the surface.
38
Provided your ETD matches the valid time on the chart, can you take off without being on an IFR flight plan out of an airport surrounded by one of the blue scalloped lines?
Yes, marginal VFR is still 3 sm + 1,000 ft ceiling or greater.
39
What if your airport is surrounded by a red line?
No, must be on an IFR flight plan.
40
Let’s say you’re flying from Nevada to Colorado. You think it would be better to get your freezing level off of this chart or the Winds Aloft?
Definitely Winds Aloft, as it will indicate
the precise freezing level for your location. This chart, on the other hand, requires heavy interpolation.
41
The dashed orange line represents areas with “moderate or greater turbulence.” What symbol does this chart use to differentiate severe and extreme turbulence from moderate?
Same dashed orange line, except the altitude shows more of the little symbols stacked up above it in order to indicate more intense turbulence.
42
What kind of chart is a Convective Outlook?
Forecast
43
What are its issue and valid times?
The Day 1 Outlook is issued 5 times/day, with the valid time specified on the chart. (Other Convective Outlooks show forecasts that extend up to 8 days, and those are issued less frequently.)
44
What weather information does this chart provide?
It shows 2 things:
1) the probability of severe convection (tornados, wind gusts 50 kts or greater, or hail 1 inch in diameter or
greater),
and 2) non-severe (general) convection.
45
What do the colors represent?
The light green TSTM areas represent non-severe (general) convection. The rest of the colors indicate areas of marginal, slight, enhanced, moderate, and high probabilities of severe thunderstorms occurring.
46
What kind of weather product is a METAR?
Observation
47
When is it issued, and what is its valid time?
Issued hourly, usually toward the end of the hour, valid at the time of observation specified on the METAR
48
What does METAR stand for?
Aviation Routine Weather Report (the acronym comes from the French translation of Aviation Routine Weather Report).
49
What kind of weather product will be released in place of a METAR in the event of a significant weather change?
A Special Weather Report, aka SPECI.
50
KSFO 121756Z 26020G27KT 200V290 R17L/2600FT VV002 FEW005 SCT015
SCT100 BKN200 18/-12 A3009 RMK AO2 RAB46 PK WND 27029/1729
WS010/18040KT LTG DSNT S OCNL LTGICCC SE CB DSNT S TS SE MOV S
SLP191 T01780117 $
51
Does this SFO METAR show VFR or IFR conditions? Why?
IFR, due to visibility (2,600 ft)
being less than 3sm, as well as the ceiling (200 ft) being less than 1,000 ft.
52
What is the ceiling?
200ft
53
Are the reported winds true or magnetic?
True
54
Is “BKN200” in MSL or AGL?
AGL. Clouds are always AGL on METARs and TAFs
55
What is the gust factor?
7 kts (difference between sustained and gusting winds).
56
What does “A02” indicate?
Is this more or less advanced than an A01?
The station is automated with a precipitation discriminator.
More
57
Does wind reported as 270@20 kts mean that the wind is blowing westbound or
eastbound?
Eastbound - the wind is coming FROM 270
58
What kind of weather would you expect to accompany a low temperature/dewpoint spread?
Clouds, possibly fog and mist . . . just more visible moisture.
59
What do the following abbreviations taken from the METAR above mean?
200v290
R17/2600FT
VV002
RAB46
PK WND 27029/1729
WS010/18040KT:
LTG DSNT S OCNL LTGICCC SE CB DNSNT S TS SE MOV S:
SLP191
TO1781117
$
200V290: wind variable between 200 and 290 degrees.
● R17L/2600FT: runway visual range for Runway 17L is 2,600 ft.
● VV002: vertical visibility is 200 ft (ceiling is indefinite, so vertical visibility becomes the
ceiling).
● RAB46: rain began 46 minutes past the hour.
● PK WND 27029/1729: peak wind was 270@29 kts occurring at 17:29Z.
● WS010/18040KT: wind shear at 1,000 ft: 180@40 kts. Put differently, the surface wind
of 260@20 gusting 27 shears to 180@40 at 1,000 ft.
● LTG DSNT S OCNL LTGICCC SE CB DSNT S TS SE MOV S: lightning distant south,
occasional lightning in-cloud and cloud-to-cloud to the southeast, cumulonimbus clouds
in the distant south, thunderstorm to the southeast moving south.
SLP191: sea level pressure is 1019.1
● T01781117: more precise temperature and dewpoint: temperature is 17.8, dewpoint
-11.7.
● $: maintenance needed
60
What kind of weather product is a TAF?
A forecast, it’s in the name
61
When is a TAF issued and what is its valid time?
Issued 4 times/day (000Z, 0600Z, 1200Z,
and 1800Z), valid for either 24 hours or 30 hours, as depicted on the TAF
62
What does TAF stand for?
Terminal Aerodrome Forecast.
63
What is the range of a TAF? In other words, the weather reported on a TAF applies to the weather extending how far out from the station?
5 sm from the center of the runway
complex
64
KACV 121740Z 1218/1318 33010KT 4SM -SHRA BR SCT002 SCT016 OVC035
TEMPO 1218/1219 BKN002 OVC016
FM122200 33010KT 6SM -TSRA SCT015 BKN020
TEMPO 1222/1302 SCT020 OVC050
FM130600 35003KT P6SM -SHRA BKN015 OVC025
FM131600 24009KT P6SM VCSH SCT025 OVC050 PROB30 1317/1318 3SM
TSRA BKN030CB
65
What does TEMPO mean?
Means that the indicated weather is expected to last for less than 1 hour, and in total, less than half the time indicated
66
Are the conditions forecast to be VFR or IFR on the 12th at 19:30?
VFR
67
At what time, or times, are conditions forecast to become IFR? Then, when do they become VFR again?
The only times IFR is forecast to occur is between 18:00 - 19:00 on the 12th.
After 19:00 the weather returns to VFR.
68
Decode -TSRA, BR, and VCSH:
Respectively: thunderstorm with light rain, mist, showers in the vicinity.
69
Would you expect lower visibility if FG or BR were reported?
FG. Fog is for < 5/8 SM; mist (BR) is used for > 5/8 SM
70
Decode “PROB030 1317/1318 3SM TSRA BKN030CB”
30% probability that the weather
between 17:00Z and 18:00Z on the 13th will drop to 3 SM vis, thunderstorms with moderate rain, and broken cumulonimbus clouds at 3,000 ft AGL.
71
AIRMET (WA), SIGMET (WS), Convective SIGMET (WST)
What is another weather product(s) that provides pilots with weather information beyond the 5 SM scope of a TAF?
AIRMETs, SIGMETs, and Convective SIGMET
72
What are the 4 types of inflight aviation weather advisories:
SIGMET, Convective SIGMET, AIRMET, and Center Weather Advisory (CWA)
73
What is a Severe Weather Watch Bulletin (WW)?
WWs supplement those 4 inflight
aviation weather advisories
74
How are inflight aviation weather advisories disseminated?
They are issued by the Aviation Weather Center (AWC) and are periodically announced by ATC to pilots in flight. Pilots can also get these while enroute from an FSS. They are obtainable on the ground through virtually all approved aviation weather sources.
75
Are these products intended for preflight planning, enroute weather advisories, or both?
both
76
Are altitudes MSL or AGL?
MSL unless stated otherwise.
77
Are AIRMETs intended for pilots of small, large, or all aircraft?
All, although they’re certainly more pertinent for smaller aircraft and pilots without instrument ratings. Put differently, an AIRMET details significant enroute weather phenomena that could be of
Of interest to all aircraft, but potentially hazardous to small aircraft
78
What is an AIRMET, and how is it different from a SIGMET?
An AIRMET is a forecast that describes significant weather occurring at intensities lower than weather requiring the issuance of a SIGMET. Generally, an AIRMET is issued for moderate weather, whereas a
SIGMET is issued for severe or greater weather
79
What does AIRMET stand for?
Airmen’s Meteorological Information
80
Define “moderate turbulence.”
Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. Usually variations in indicated airspeed will occur. Occupants feel definite strains against seat belts or shoulder straps. Unsecured objects are dislodged. Food service and walking are difficult
81
What are the issue and valid times for AIRMETs?
Issued every 6 hours, valid for 6 hours.
Includes an outlook describing the weather over the next 6 hours. Unscheduled amendments and updates are issued as required.
82
What are the three types of AIRMETs, and what type of weather is included in each?
For all of the following, when the weather phenomena are occurring or are expected to occur over an area of at least 3,000 square miles:
● Tango: moderate turbulence, sustained surface wind greater than 30kts, and/or
non-convective low-level windshear potential below 2,000 ft AGL.
● Sierra: extensive IFR conditions (less than 3 sm vis or 1,000 ft ceiling) and/or mountain obscuration.
● Zulu: moderate icing with freezing level heights
83
Would the existence of an AIRMET Tango en route for moderate turbulence affect your go/no-go decision? In what way?
Possibly, although probably not. I would investigate further to see if the turbulence exceeded my personal mins. If able, I would plan around the affected area.
84
Are SIGMETs intended for pilots of small, large, or all aircraft?
All aircraft, but unlike AIRMETs, SIGMETs indicate weather that is potentially hazardous to all aircraft.
85
What does SIGMET stand for?
Significant Meteorological Information
86
What are the issues and valid times for a SIGMET?
Issued as necessary, valid for up to 4
hours, except that SIGMETs involving tropical cyclones and volcanic ash are valid for 6 hours. Updates and corrections issued as necessary
87
What type of weather is included in a SIGMET
For all of the following, when the
non-convective weather phenomena are occurring or are expected to occur over an area of at least 3,000 square miles:
● Severe or extreme turbulence or clear air turbulence not associated with thunderstorms.
● Severe icing not associated with thunderstorms.
● Widespread dust storm or sandstorm lowering surface visibilities to below 3 miles.
● Volcanic ash.
88
Define “severe turbulence.”
Severe turbulence causes large, abrupt changes in altitude and/or attitude, usually accompanied by large variations in indicated airspeed. Aircraft may be momentarily out of control.
89
How would the existence of a SIGMET along your flight path affect your go/no-go decision?
I would plan around it. If unable, I’d make a no-go decision.
90
What is a Convective SIGMET, and how is it different from a SIGMET?
The keyword/differentiator is “convective” - so unlike SIGMETs, Convective SIGMETs sound the alarm on more extreme weather associated with thunderstorms. To quote the AIM directly: a Convective SIGMET may be issued for any convective situation that the forecaster feels is hazardous to all categories of aircraft.
91
What are the issue and valid times for a Convective SIGMET?
Issued hourly 55 minutes past the hour, updated as required. Valid for up to 2 hours.
92
What type of weather is included in a Convective SIGMET?
● Severe thunderstorms due to:
- Surface winds greater than or = to 50 kts.
- Hail at the surface greater than or equal to ¾ inches in diameter.
- Tornadoes.
● Embedded thunderstorms.
● A line of thunderstorms.
● Thunderstorms producing precipitation greater than or equal to heavy precipitation affecting 40 percent or more of an area of at least 3,000 square miles.
93
If a Convective SIGMET does not mention turbulence or icing or wind shear, does that mean you can expect smooth air and no icing?
No, any Convective SIGMET implies
severe or greater turbulence, severe icing, and low-level wind shear.
94
What is a Center Weather Advisory (CWA)?
This is an unscheduled in-flight weather
advisory used to supplement AIRMETs/SIGMETs/Convective SIGMETs. The FAA describes a CWA as a “nowcast” for conditions developing in the next 2 hours
95
Graphical Area Forecast (GFA)
What is the GFA tool, and what is it used for?
The GFA provides aviation weather
information to give users a complete visual picture of the weather that may impact their flights. Users can select for virtually any type of weather, time, altitude, and flight path.
96
How often is GFA information updated, and what are its valid times?
Updated continuously, valid for the selected times. Users can select FORECAST for a range of valid times that extend 15 hours into the future, or select OBSERVATION for valid times in the previous 14 hours
97
PIREP
Interpret this PIREP:
KCMH UA
/OV APE 230010
/TM 1516
/FL085
/TP BE20
/SK BKN065
/WX FV03SM HZ FU
/TA 20
/TB LGT
/IC MDT MXD 040-050
/RM LLWS –15 KT
SFC-030 DURGC RY 22 CMH
Nearest station: KCMH, message type: routine (non-urgent) report.
/Location: weather occurred 10DME out on the APE 230 degree radial.
/ Time: the time that reported weather occured was 15:16Z.
/ Altitude: The altitude where the weather was encountered is 8,500 ft MSL.
/ Aircraft type: type of aircraft reporting the PIREP is a BE20.
/ Sky condition: broken at 6,500 ft MSL.
/ Flight visibility and weather: 3 SM due to haze and smoke.
/ Air temperature: 20 degrees.
/ Turbulence: light.
/ Icing: moderate mixed iced
between 4,000 - 5,000 ft MSL.
/ Remarks: low-level wind shear, pilot reported minus (a loss of) 15 kts between the surface and 3,000 ft during climb out from runway 22 at CMH airport.
98
Who do you contact to file a PIREP?
ATC or an FSS.
99
What would “UUA” (instead of UA) signify on a PIREP?
Urgent
100
What are some ways to check for PIREPs on the ground as part of your preflight planning?
How about in-flight?
On the ground, you can use Foreflight, aviationweather.gov, 1800wxbrief.com, or call a briefer.
In the air, you can talk to ATC or an FSS.
101
What is the procedure for filing a PIREP?
PIREPs can be filed en route with either ATC or an FSS. The AIM advises against being overly concerned with strict format or phraseology: “The important thing is that the information is relayed so that other pilots may benefit from your observation.” Pilots should simply give position, time, altitude, type aircraft, and a description of the weather (sky cover, flight vis, precip, restriction to vis, temp, wind direction and strength, turbulence, icing, additional remarks)
102
Are altitudes in a PIREP reported in MSL or AGL?
MSL, unless noted otherwise
103
FSS Weather Briefings
Describe the 3 types of weather briefings pilots can request from an FSS briefer. When should each be used?
● Standard briefing: A standard weather briefing provides a complete picture of the
weather and is the most detailed of all briefings. It includes adverse conditions, VFR flight not recommended (if applicable), a synopsis, current conditions, en route forecast, destination forecast, winds and temps aloft, NOTAMs, prohibited areas and SFRAs, ATC delays, and other information specifically requested by the pilot. This type of briefing should be obtained prior to the departure of any flight.
● Abbreviated briefing: This is a shortened version of the standard briefing that should be requested when a departure has been delayed or when specific weather information is needed to update a previous standard briefing
● Outlook briefing: This briefing should be requested when a planned departure is 6 or more hours away. It provides initial forecast information that is limited in scope, but that can influence decisions regarding route of flight, altitude, and ultimately the go/no-go decision. A follow-up standard briefing prior to departure is advisable.
104
Atmospheric Composition and Stability
Describe the composition of the Earth’s atmosphere.
78% nitrogen, 21% oxygen, and then
the last 1% is made up of argon, carbon dioxide, and other gasses.
105
What is the atmosphere?
What is its purpose?
It’s a cloud of gas and suspended solids
extending from the surface out many thousands of miles, held in place by the Earth’s gravitational pull.
It’s a protective bubble that holds oxygen, moisture, gases, and tiny particles, and that essentially protects us from outer space.
106
The Earth’s atmosphere is divided into 5 concentric layers. In what layer do we fly, and up to what altitude does it extend?
Troposphere. It extends up to approximately 36,000 ft. Jets can fly above this in the stratosphere
107
Temperature and pressure-wise, what is the standard composition of the troposphere?
For every 1,000 ft of altitude gained, the temperature decreases by 2 degrees C, and the pressure decreases by 1 inch Hg.
108
What does it mean to say that an atmosphere is “stable”?
“Stability” refers to the atmosphere’s ability to resist vertical movement of the air. I.e., if a parcel of air gets pushed upward in a stable atmosphere, it will quickly cease rising or even get pushed back down;
whereas a parcel of air pushed upward in an unstable atmosphere will continue rising.
109
What kind of weather would you expect to form in an unstable atmosphere?
Turbulent airflow, clouds with extensive vertical development, and just generally convective activity.
110
What two things determine the stability of the air?
Temperature and moisture
111
If the air is cool and dry, would this be indicative of a stable or unstable atmosphere?
How about warm and wet air?
Why?
Stable
Unstable
Warm air is more inclined to rise, and wet air has more water vapor
(which is lighter than air molecules) So it’s less dense and even more inclined to
rise.
112
What does “adiabatic lapse rate” refer to?
As air rises into an area of lower pressure, the
molecules of air expand, giving off heat, causing the air temperature to drop at an average rate of 2 degrees C per 1,000 ft of altitude gain.
Completely dry air tends to decrease in temperature by about 3 degrees per 1,000 ft as it rises (aka “dry adiabatic lapse rate”)
whereas moist air decreases anywhere from 1.1-2.8 degrees C (aka “moist adiabatic lapse rate”).
113
Wind (e.g. crosswind, windshear, mountain wave, etc.)
What causes wind to form?
Uneven heating of the Earth’s surface causes density and pressure changes in the atmosphere, and air then flows from high to low pressure.
Additionally, the Coriolis force contributes to air movement.
114
What’s the difference between “wind” and “convective currents”?
The former moves horizontally - the latter moves up and down.
115
Why can it be dangerous to take off with a tailwind?
Because a higher ground speed is
required, meaning more stress on the tires and gear while on the ground, a longer takeoff roll, and a shallower climb angle.
116
You’re flying from California to Florida. There is a high-pressure system along your route.
Would you get more favorable winds flying along the north or south side of the high-pressure system, and why?
North - wind flows clockwise around a high-pressure system.
117
Flying over pavement on short final, would you expect up or downdrafts?
How about over water or areas of vegetation like a group of trees?
Updrafts
Downdrafts
118
Describe how land breezes and sea breezes form.
During the day, land heats faster than
water, so the air over the land becomes warmer and less dense. It rises and is replaced by cooler, denser air flowing in from over the water. This causes an onshore wind called a sea breeze.
Conversely, at night land cools faster than water, as does the corresponding air. In this case, the warmer air over the water rises and is replaced by the cooler, denser air from the land, creating an offshore wind called a land breeze.
119
What are mountain waves?
Where do they form?
They are turbulent waves that form when stable air flows over a mountain or mountain ridge
They form above and downwind of mountains, extending up to 600 miles downwind from the mountain range, and up to (and even above) the top of the troposphere.
120
What type of cloud indicates the presence of mountain waves?
Lenticular
121
In windy conditions, would you expect more favorable conditions approaching a mountain from the windward or leeward side?
Why?
Windward.
As the air flows down
the leeward side of the mountain, the air follows the contour of the terrain and is
increasingly turbulent. This tends to push an aircraft into the side of the mountain. The
stronger the wind, the greater the downward pressure and turbulence become.
Downdrafts can be severe.
122
What technique should pilots use if flying low-level over a mountain range?
Cross the range at an angle, making it easier to turn around if necessary.
123
Moisture/Temperature
When it’s hot outside, can the air hold more or less moisture than when it’s cold?
More
124
Define “dew point.” Then put it in layman’s terms
Dew point is the temperature at which
the air must be cooled to become fully saturated.
In layman’s terms, this means that the dew point is the temperature at which the air can hold no more moisture/water vapor - if the temperature drops further, then the water vapor becomes a visible liquid, i.e., it condenses
125
What does a high dew point indicate?
This indicates that there is more moisture in the air.
126
Explain relative humidity
Relative humidity is the actual amount of moisture in the air compared to the total amount of moisture the air could hold at that temperature.
So, a relative humidity of 65 percent means that the air is holding 65 percent of the total amount of moisture that it is capable of holding
127
What would feel muggier, an atmosphere with a temperature of 80 degrees F and a
dew point of 70 degrees F;
or a temperature of 50 F and a dew point of 50 F (so 100% relative humidity)?
The former - the dew point is higher, meaning there’d be more moisture in the air.
128
What effect does the formation of water vapor (evaporation) have on the temperature?
A cooling effect.
129
Define the following:
Evaporation:
Sublimation:
Condensation:
Deposition:
● Evaporation: liquid to gas/vapor. (E.g. sweat evaporating, or a lake drying up.)
● Sublimation: solid to gas/vapor. (E.g. dry ice.)
● Condensation: gas/vapor to liquid. (E.g. cloud/dew formation.)
● Deposition: gas/vapor to solid. (E.g. frost.)
130
Precipitation
What dangers can precipitation pose to pilots?
It can reduce visibility, create icing
situations through freezing rain or runway icing, negatively affect landing and takeoff
performance, and contaminate fuel tanks and engines.
131
How does precipitation form?
It forms when water or ice particles in clouds grow (through collision and coalescence) to a sufficient size such that the atmosphere can no longer support them.
132
What three ingredients are necessary for the formation of precipitation?
Water vapor,
sufficient lift to condense the water vapor into clouds,
and a growth process that allows cloud droplets to grow large and heavy enough to fall as precipitation.
133
What are the various types of precipitation?
Rain, drizzle, snow, ice pellets/crystals, hail.
134
What do ice pellets and freezing rain indicate in terms of the temperature makeup of the
atmosphere?
They indicate a temperature inversion above.
The formation of both types of precipitation requires the precipitation to pass through a cold/freezing temperature layer, then a warm/above-freezing layer, then back through a cold layer, where the precipitation
either refreezes as ice pellets or becomes supercooled/freezing rain
135
What is virga?
Precipitation that evaporates before hitting the ground.
136
Weather System Formation Including Air Masses and Fronts
What is a front, and how does one form?
A front is the boundary layer between two types of air masses.
An air mass is a large body of air that takes on the characteristics of the surrounding area or source region, generally classified as tropical or polar. As an air mass moves across a body of water or land, it eventually comes in contact with another air mass, resulting in the formation of a front.
137
When does a cold front occur?
When a mass of cold, dense, and stable air advances and replaces a body of warmer air.
138
Describe the typical dimensions/shape and speed of a cold front.
Cold fronts move rapidly, progressing at a rate of 25-30 mph. They are shaped like a snow plow, sliding under the warmer, less dense air and forcing it aloft.
139
What is a sign of imminent cold front passage?
A high dew point and a falling
barometric pressure.
140
What kind of weather would you expect to accompany a passing cold front?
The weather changes suddenly as the steep slope of the fast-moving cold front hits, often
with little or no warning; towering cumulus or cumulonimbus clouds dominate the sky,
accompanied by heavy showery precipitation, unstable air, lightning, thunder, hail, poor
visibility, winds variable and gusty, temperature and dew point drop rapidly, pressure bottoms out then begins a gradual increase. After passage, the weather clears rapidly. Good visibility and drier air prevail, along with colder temperatures and rising pressure
141
When does a warm front occur?
When a warm mass of air advances and replaces a body of colder air.
142
What kind of weather would you expect to accompany a passing warm front?
The front gives plenty of warning, then passes slowly, causing the weather to change gradually: warm, humid air gradually slides over the top of a relatively colder air mass, pushing the cold air away, leading to warmer temperatures, low ceilings and low visibilities with fog, stratiform clouds, steady continuous precipitation, drizzle, sleet, rain, and snow.
When the warm front’s air is unstable (common in the summer), thunderstorms and convection can occur. Warm fronts take days to pass through a region, so the steady precipitation and low vis and stratiform clouds tend to linger after the front passes
143
What is a stationary front?
A stationary front occurs when the forces of two air masses are relatively equal, and the boundary (or front) that separates them remains stationary and influences the local weather for days
144
What kind of weather would you expect to accompany a stationary front?
A mixture of weather found in warm and cold fronts
145
What is an occluded front?
This is when a fast-moving cold front catches up to a slow-moving warm front, forcing the warm air aloft.
146
What kind of weather would you expect to accompany the passage of an occluded
front?
A mixture of weather is found in warm and cold fronts: usually, as the occluded front approaches, expect warm front weather; this is immediately followed by cold front weather
147
Describe a warm vs cold front occlusion.
A cold front occlusion occurs when the fast-moving cold front is colder than the air ahead of the slow-moving warm front.
A warm front occlusion occurs when the cold front’s air is warmer than the air ahead of the
warm front.
148
Which generally produces worse weather, a warm or cold occluded front?
The weather is more likely to be severe and convective during a warm front occlusion, provided that the warm air being forced aloft is unstable
149
What kind of weather is generally associated with a low pressure system?
Inclement
150
What direction does the wind flow around a low pressure system?
Counter-clockwise, inward, and upward.
151
What kind of weather is associated with a high-pressure system?
Generally more favorable
conditions, with light winds
152
Describe the airflow around a high pressure system.
Clockwise, outward, and
downward.
153
Clouds
What qualifies as a ceiling?
FAA’s definition: Lowest cloud layer or obscuring phenomena reported as “broken,” “overcast,” or “obscuration,” and not classified
as “thin” or “partial.”
ICAO definition: The height above the ground or water of the base of the lowest layer of cloud covering more than half the sky.
154
What causes clouds to form?
The water vapor in rising air currents cools to its dew point and condenses onto miniscule particles of matter (like dust/salt/smoke) into visible moisture.
155
Clouds are classified using the following nomenclature - describe each:
● Cumulus: look like fluffy cotton balls - heaped or piled clouds. Bases are usually
low-middle clouds, but tops can extend up to 60,000 ft.
● Stratus: layered clouds. Usually low-level.
● Cirrus: thin, wispy, high-level clouds usually composed of ice crystals.
● Castellanus: cloud with a common base but with separate vertical development, castle-like.
● Lenticular: lens-shaped cloud that forms over mountains in strong winds.
● Nimbus: rain-bearing clouds.
● Fracto: ragged or broken clouds.
● Alto: middle-level clouds existing between 5,000 to 20,000 ft
156
What is the most dangerous cloud type to pilots?
Cumulonimbus.
157
What are the approximate altitude cutoffs that define low, middle, and high clouds?
Low: surface - 6,500 AGL;
Middle - 6,500 AGL - 20,000 AGL;
High - above 20,000 AGL.
158
What would you do if approaching a cloud shaped like a lens (or like a flying saucer)
positioned directly above some mountains.
Why?
Avoid it by a wide margin.
Lenticular clouds form from mountain waves, thus, they indicate excessive turbulence/winds.
159
Turbulence
What are the 3 causes (or types) of turbulence? Describe each.
Convective: uneven heating of the Earth’s surface on summer afternoons with little wind causes bubbles of warm air to rise, leading to rising and sinking air currents. Billowy cumuliform clouds on sunny afternoons are an indication of such turbulence.
Mechanical: caused by obstructions that disrupt smooth wind flow, instead creating
eddies that get carried downstream. Mountain waves are one form of mechanical
turbulence, as is turbulent air around airports caused by the wind flow colliding with
hangars and buildings, and other obstructions.
Wind shear: This turbulence is generated between two wind currents of different
directions and/or speeds. Temperature Inversion boundary layers and Clear Air
Turbulence (usually occurring between the jet stream and surrounding air) are two
forms of this.
160
What are the 4 levels of turbulence intensity, and what defines each?
❏ Light: causes slight changes in altitude and/or attitude. Occupants may feel slight strain against their seat belts. Unsecured objects may be displaced.
❏ Moderate: causes changes in altitude and/or attitude and indicated airspeed, but
positive control is maintained. Occupants feel definite strains against seat belts. Unsecured objects are dislodged.
❏ Severe: causes large changes in altitude/attitude and large variations in indicated airspeed. Aircraft may be momentarily out of control. Occupants are forced violently against their seat belts.
❏ Extreme: causes aircraft to be violently tossed about, rendering it practically impossible
to control. May cause structural damage.
161
In windy conditions, why should pilots be on high alert for turbulence when overflying
mountains?
What causes these?
Due to mountain waves
Wind flowing perpendicular to the mountains gets pushed aloft causing up/downdrafts and waves.
162
At what altitudes is clear air turbulence (CAT) a very serious operational factor to flight
operations?”
What is the best way to determine the location of CAT before a flight?
All. Especially above 15,000 MSL, though
PIREPs
163
Would you expect to encounter less turbulence flying through a small thunderstorm than through a large one?
No, there’s no useful correlation between the external visual appearance of thunderstorms and the severity or amount of turbulence or hail within them.
164
Thunderstorms/Microbursts
What ingredients are necessary for a thunderstorm to form?
Are all three always required?
Sufficient water vapor, an unstable lapse rate( unstable atmosphere), and an initial lifting action.
Yes
165
In terms of thunderstorm formation, must the moisture in the air be visible?
No, water vapor is sufficient.
166
What charts can you use to determine the presence of each ingredient?
Plenty of options here. One viable answer: for moisture look at the dewpoint - a higher dew point means more water vapor; for instability look at the temperature lapse rate on the winds aloft chart; for a lifting action look at the surface analysis and/or prog chart for low pressure systems, frontal activity, etc
167
What is “unstable” air?
Air that, when pushed upward, continues rising. Conversely, stable air resists upward movement.
168
What are some examples of weather phenomena that can cause a lifting action?
Orographic effects (wind moving upward across mountains and valleys), frictional effects (low pressure systems), frontal lifting, buoyancy (uneven heating of surface), converging winds around surface lows and troughs, drylines, outflow boundaries generated by prior storms, and local winds, such as sea breeze, lake breeze, land breeze, and valley breeze circulations
169
Explain each stage of a thunderstorm
● Cumulus: strong updrafts push warm, moist air upward until all the moisture becomes
too heavy for the clouds to support.
● Mature: The moisture, too heavy now for the updrafts and clouds to support, falls in the form of precipitation. When the precipitation reaches the surface, the mature stage begins. Precipitation descends through the cloud and drags the adjacent air downward, creating strong, cool downdrafts alongside the warm updrafts.
● Dissipating: Characterized mostly by downdrafts, which replace the updrafts, effectively cutting off the supply of moisture provided by the updraft. Precipitation tapers off and ends.
170
What are the three principle thunderstorm types?
Explain each
● Single-cell (aka airmass): like it sounds, a one-cell thunderstorm. Usually lasts 30
minutes. Easily circumnavigated by pilots. These are rare.
● Multi-cell (aka steady-state): A multicell thunderstorm consists of a cluster of cells at
various stages of their life cycles. With an organized multicell cluster, as the first cell
matures, it is carried downwind, and a new cell forms upwind to take its place. A
multicell cluster may have a lifetime of several hours (or more). New cells will continue
to form as long as the three necessary ingredients exist.
● Super-cell: This is an especially dangerous convective storm cell that consists primarily
of a single, quasi-steady updraft that persists for an extended period of time. Updraft
speeds may reach 9,000 feet per minute. Nearly all supercells produce severe weather
(large hail, damaging wind), and about 25 percent produce a tornado. These persist for
many hours and can be part of multicell storms as well.
171
Generally, what causes airmass vs steady-state thunderstorms to form?
The former usually form on hot afternoons due to surface heating, whereas the latter are associated with weather systems, like fronts or converging winds or troughs.
172
What is it called when thunderstorms form in a line, continually re-forming at the leading edge of the system, extending laterally for hundreds of miles?
Squall line
173
During what stage do weather hazards generally reach peak intensity?
End of the mature stage.
174
What marks the end of the mature stage?
Anvil cloud top
175
How long is the typical life cycle of a single thunderstorm cell?
About 30 minutes
176
What clouds produce thunderstorms?
Cumulonimbus.
177
Should you always expect thunder and lightning in a thunderstorm?
Yes, always
178
What other kinds of weather would you expect?
Strong winds, icing (including freezing
rain), hail, heavy rain, and sometimes tornadoes
179
You’re flying at night and find that you’ve flown into a thunderstorm. What procedures does the AIM recommend pilots follow here?
Verify pitot-heat and defroster are on; set a power setting (and generally don’t adjust it) to maintain an airspeed below Va; keep your eyes on your instruments, not outside; maintain a constant attitude while allowing the altitude and airspeed to fluctuate; don’t turn back once you are in the thunderstorm as turning maneuvers increase stress on the aircraft; turn up cockpit lights to highest intensity to lessen temporary blindness from lightning; disengage auto-pilot, if equipped
180
Why is it important to disengage the autopilot, if equipped?
The autopilot will mask the
Effects of icing/an impending stall. The autopilot will also try to maintain altitude,
heading, and airspeed, despite the fact that proper technique for flying in a
thunderstorm involves simply maintaining a pitch attitude and riding the waves, so to
speak.
181
If you accidentally fly into a thunderstorm, what airspeed will you fly?
Little below maneuvering speed.
182
If you’re stuck in one would you try to maintain a level altitude or level attitude?
Attitude. Doing otherwise could overstress the aircraft.
183
By how many miles are you supposed to circumvent a thunderstorm? Why?
20 miles, to avoid hail and strong winds
184
Let’s say you see a thunderstorm ahead along your victor airway, it seems to be moving to
the right and it’s clear to the left, what are you going to do/say to ATC?
“Center, Cessna ____, request to deviate approximately _____ degrees left of course for weather avoidance.”
185
What does the METAR symbol -TSRA mean?
It means LIGHT RAIN associated with a thunderstorm.
186
Is flying under a thunderstorm safe?
No
187
As you turn final at your destination airport, you notice virga just above the runway. Your
indicated airspeed starts increasing despite that fact that you’re not adding power, nor are you descending any more rapidly... What do you think is going on here?
You’re approaching a microburst.
188
Is this a dry or a wet microburst?
Dry
189
What additional sign might you see at the surface of a dry-type microburst?
A blowing ring of dust.
190
What are you going to do?
Add full power and start climbing - go around. If you’re already in the microburst, climb straight ahead; if you’re approaching the microburst but not yet in it, immediately turn around while climbing.
191
How strong can the downdrafts get?
How about the horizontal winds?
6000 ft/min
45kts (90kt shear)
192
How long would you expect this microburst to last?
15 minutes.
193
What sort of weather activity needs to exist for a microburst to form?
Convective
194
Icing and Freezing Level Information
Pretend that the weather at your destination airport at your ETA is this: 071653Z 03004KT
10SM OVC040 07/02 A3029 RMK AO2 SLP260 T00670017. You intend to file an IFR, and this airport has multiple approaches. Would you make a go or no-go decision?
Why or why not?
No-go due to icing. With a normal lapse rate the temp at 4000ft would be -1 degrees, and the ceiling is overcast at that altitude.
195
Show me with your charts and weather information how exactly you determined that we won’t be at risk of flying into icing conditions
This will involve using the charts to both show where the clouds/visible moisture will be during every phase of the flight, as well as to
determine the freezing level throughout the route. There are many ways to effectively do
this. Some options: as the TAF range extends only 5 sm from the airport, and seeing as
only larger airports have TAFs, determining cloud coverage beyond the range of these
airports involves using the Graphical Area Forecast (GFA). The GFA tool on aviationweather.gov allows you to plot your flight path, then it shows the cloud coverage
along the entire route at various selected times. Determining precise freezing levels along your route involves using the winds aloft chart - be sure to use the stations along the entire route, not just departure and destination airport stations. More options include using graphical icing forecasts, PIREPs, freezing level charts, etc. Using the “show flight path” feature is always extremely helpful, as it allows you to prove the location of this weather relative to your exact route
196
What kind of weather conditions need to exist for structural icing to form?
Must this moisture be visible?
Temperatures around freezing (close enough for the surface of the plane to be at or below 0 degrees C) and visible moisture
Yes
197
What are the different types of ice, and what characterizes each?
Clear
Rime
Mix
198
What temperature ranges correspond to the formation of each of these types of structural
ice?
199
How can you use the weather charts to determine whether there’s a possibility of freezing rain along the route?
Other than just looking for any thunderstorms or PIREPs, look for
temperature inversions on the winds aloft coupled with precipitation on the radar summary, GFA, or METARs/TAFs
200
What are the different intensity levels of structural icing that one can report to ATC?
Trace, Light, Moderate, Severe.
201
Fog/Mist
Tell me about every type of fog, and in particular, what causes each type to form.
● Radiation fog: Forms on clear nights with little to no wind when the ground cools rapidly due to terrestrial radiation, causing the surrounding air temperature to cool to its dew point.
● Advection fog: Common in coastal areas with sea breezes (winds up to 15kts are
usually required), advection fog occurs when the wind pushes the layer of warm, moist
ocean air over a cold terrestrial surface, which cools the moist air to the dew point.
● Upslope fog: Occurs when wind forces moist, stable air up sloping land features like a mountain range until the moist air cools to the dew point.
● Steam fog/sea smoke: Forms when cold, dry air moves over warm water - as the water
evaporates it rises and resembles smoke.
● Ice fog: Like radiation fog, except involving extremely cold, arctic temperatures that
cause the water vapor in the air to form directly into ice crystals.
202
Transcribe this METAR: KYYQ 301300Z 35011KT 1/8SM FG VV001 02/02 A2991 RMK
SLP131
What is the ceiling?
100ft. Any time there is completely obscuring phenomena (in this case fog), the Vertical Visibility (VV) is listed, and that becomes the ceiling.
203
What kind of illusion would you expect when you’re approaching to land and you enter fog?
Entering fog gives the sudden feeling of pitching up, causing the pilot to pitch the nose
down.
204
What can you do to mitigate this?
Rely on your instruments, and use visual aids like PAPI’s/VASI’s.
205
What’s the difference between fog and a cloud?
Fog is just a cloud that is on the surface.
206
If the METAR shows a temperature of 5 and a dew point of 4, what sort of weather would
you expect?
Visible moisture. Mist, fog, clouds.
207
Frost
What causes dew to form?
Dew collects when a surface - like a blade of grass, or the skin of the airplane - cools below the dewpoint, causing the water vapor (i.e. the gas form of water) to condense (become a visible liquid).
208
What causes frost to form on an airplane?
Frost occurs when the temperature of the
surface of the airplane cools below the dewpoint and below freezing (O degrees C)
209
On what type of nights is frost most likely to form?
Cool, clear, calm nights with a low dew
point.
210
Why is it a bad idea to take off with frost on the wings?
Because frost increases drag and
decreases lift. Also it’s illegal.
211
What kind of drag does frost cause?
Parasite - skin friction.
212
Obstructions To Visibility (e.g. smoke, haze, volcanic ash, etc.)
What is smoke, and what causes it?
Smoke is a suspension in the air of small particles produced by combustion due to fires, industrial burning, or other sources
213
What makes it dangerous to pilots?
It can reduce visibility, its compounds can be highly toxic or irritating, and it can contain carbon monoxide.
214
Why does smoke take longer to dissipate than fog or mist?
Fog and mist can dissipate through evaporation or through the movement of air (wind); smoke doesn’t dissipate - it requires the movement of air.
215
What is haze?
Haze is the suspension in the air of extremely small particles invisible to the naked eye and sufficiently numerous to give the air an opalescent (multi-colored, shimmering) appearance.
216
How does haze reduce visibility?
By scattering light.
Visibility in haze varies greatly, depending on whether the pilot is facing into or away from the sun. Above the definite ceiling of the haze layer the visibility is unrestricted, whereas at or below the ceiling the slant range visibility (air-to-ground) is poor
217
How is haze different from mist and fog?
In terms of density, haze is the least dense
(increasing in density to mist, then fog). Also, haze appears blue or yellow, depending on the position of the sun, whereas mist and fog generally appear gray.
218
Why is it dangerous to fly through volcanic ash?
Volcanic ash is made up of fine particles
of rock powder called “silica” (glass) that, if ingested by the engine, can melt and produce a soft sticky molten product that adheres to internal parts of the engine. Ash also causes
abrasive damage to aircraft flying through it at hundreds of miles per hour - particles
impacting the windshield can sandblast the surface into a frosted finish that obscures the
pilot’s view.
219
Can ATC radar detect the presence of volcanic ash?
No - weather radar can, though.
220
What kind of weather would legally require us to be on an IFR flight plan in order to take off
today out of KIWA?
Anything below VFR T/O mins, i.e., below either 3sm OR 1000ft ceiling
When departing from a controlled airport.
221
What about out of KCGZ (uncontrolled airport)?
Vis below 1sm OR if you can’t maintain
clear of clouds.
