Wx Theory + Wx Services Flashcards
What happens when warm, moist, stable air flows upslope
It produces stratus type clouds
What type of cloud is forecast in a TAF?
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.
Which inflight advisory would contain information on severe icing not associated with thunderstorms?
SIGMET
What are two ways to determine PA?
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)
Why is DA useful? How do you calculate it?
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.
What are the types of weather briefs from FSS?
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
What is a graphical forecast for aviation (GFA) used for?
To best determine general forecast weather conditions covering a flight information region
What situation is most conducive to the formation of radiation fog?
Warm, moist air over low, flatland areas on clear, calm nights.
If an unstable air mass is forced upward, what type of clouds can be expected?
Clouds with considerable vertical development and associated turbulence.
What should you do if you encounter severe turbulence?
Upon encountering severe turbulence, the pilot should attempt to maintain a level flight attitude.
What is the relationship between weather and heat exchange?
Every physical process of weather is accompanied by or is a result of a heat exchange
What affects the amount of water vapor that air can hold?
The amount of water vapor which the air can hold depends on air temperature
What is ATIS
ATIS is the continuous broadcast of recorded information concerning non-control information in selected high activity terminal areas
What’s the effect of warming from below, upon the stability of the airmass
Warming from below would decrease the stability of an air mass.
Explain NOTAM
NOTAM - notice to air mission. NOTAMs contain aeronautical information that could affect the decision to make a flight.
What is necessary for the formation of fog?
a small temp-dew point spread
What is associated with steam fog?
Steam fog is associated with hazardous low-level turbulence & icing
Describe the formation of thunderstorms
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.
How are clouds categorized?
Clouds are divided into four families according to their height range.
What happens when the relative humidity is high beneath a low-level temperature inversion layer?
The weather conditions that can be expected include smooth air and poor visibility due to fog, haze, or low clouds.
How do you read winds aloft forecast when winds are forecast above 99 kts?
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.
What is indicated by a current convective SIGMET?
Thunderstorms obscured by massive cloud layers.
A pilot can expect a wind shear zone in what temperature inversion conditions?
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.
What conditions are favorable for clear ice accumulation?
freezing rain below a frontal surface.
When telephoning flight service for preflight weather information pilots should state: (11 items)
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.
Which conditions result in the formation of frost?
The temperature of the collecting surface is at or below the dew point of the adjacent air and the dew point is below freezing.
What is a characteristic of stable air?
Stratiform clouds. (since stable air resists convection, clouds in stable air form in horizontal, sheet-like layers or “strata”)
Two conditions are necessary for structural icing in flight:
A condition favorable for structural icing is freezing _____
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.
Characteristics of an unstable air mass include ___ clouds, showery ___, rough ____, and good ___
cumuliform clouds, showery precipitation, rough air (turbulence), and good visibility (except in blowing obstructions)
Possible mountain wave turbulence could be anticipated when winds of __ knots or greater blow across a mountain ridge, and the air is stable/unstable.
40
STABLE
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.
5000
5
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
9900
5 kts
Dew point is the temperature to which air must be cooled to
Become saturated by the water vapor already present in the air
Clouds, fog, or dew will always form when
water vapor condenses
Pressure altitude is equal to true altitude under____
Standard atmospheric conditions
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
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
What is a TAF?
PROB40
TX 20/1819Z
TN 10/1910Z
P6SM
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
Types of AWOS reports
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).
Standard sea level pressure
1013.2 millibars
What are the types of icing? When is icing most likely
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.
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.
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.
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 _______.
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.
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.
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.
Air flows from areas of ____ to ___ pressure b/c air always seeks out areas of ___ pressure.
Air flows from areas of high to low pressure b/c air always seeks out areas of low pressure.
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.
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.
