A107 WEATHER THEORY AND REPORTS Flashcards
What is the Atmosphere
made up of?
~ 78% Nitrogen, 20% Oxygen and
2% other gases
What does the atmosphere contain?
Swirls, eddies, currents, and waves –
like the ocean
What are the 4 layers of the Atmosphere?
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
What layer of the atmosphere contains the jetstream?
Tropopause
Altitude varies with location and wx
Where is the tropopause located?
At the top of the troposphere is a boundary known as the tropopause, which traps moisture and the
associated weather in the troposphere.
Where does the vast majority of weather, clouds, storms, and temp variances occur?
Troposphere
What is the major factor in circulation?
uneven heating of the earth’s surface by the sun
Earths rotation is referred to as the ______________?
Coriolis Effect
Air Circulation Patterns follow what direction?
Right
Air flows ________ around high-pressure areas, and
_____________ around low-pressure areas
Clockwise, Counter-clockwise,
________ refers to air moving horizontally from high pressure to low pressure
Wind
As warmer air rises and small vertical air movements tend to become larger, what does that generate?
Turbulence and convective wx
What is the Standard Temperature Lapse Rate?
2 deg C every 1000’ altitude increase
Stable atmosphere makes ___________ _____________ difficult
Vertical Movement
What is a Temperature Inversion?
An atmospheric anomaly where air gets warmer as altitude increases to a certain point.
Can result in restricted visibility
Define Air Masses
Large bodies of air that take on characteristics of the surrounding area
An air mass passing over a __________ surface is warmed from below and
convective currents form causing the air to rise
Warmer
An air mass passing over a _________ surface does not form convective
currents, but creates a stable air mass with poor visibility
Colder
What is a warm front?
Warm, humid air moves to replace a body of cold air
* Light to moderate precipitation probable
* Blanket type clouds (Stratus) likely
What are the characteristics of a Cold Front?
- Cold, dense, stable air rapidly advances to displace a body of warmer air
- Stays close to the ground, acts like a snow plow
Generally more severe wx than warm fronts
Clouds are classified by?
- By shape
- According to the height of their bases (Low, Middle or High)
- According to their behavior or vertical development
Low clouds are below what AGL?
6500’
From _______ to _________ ft AGL is the middle layer of clouds?
6500’ to 20,000’
High clouds are above what AGL?
20,000’
Low Clouds are?
Fog
* Surface to 6,500’ AGL
* Made primarily of water droplets, but can include supercooled water droplets
Middle Clouds are?
- 6,500’ AGL to 20,000’ AGL
- Composed of water, ice crystals and supercooled water droplets
High clouds are?
- Form above 20,000 AGL
- Form in stable air
- Composed of ice crystals
What are clouds with extensive vertical development?
- Cumulus clouds that build vertically to towering cumulus or cumulonimbus clouds
What are the Three Stages of a Thunderstorm?
Cumulus (mostly updrafts)
Mature (both up and downdrafts)
Dissipating (mainly downdrafts)
What is the most violent stage of a Thunderstorm?
Mature Stage (precipitation begins to fall with both updrafts and downdrafts)
What are some Thunderstorm hazards to aviation?
- Updrafts / Downdrafts
- Large Hail-stones
- Lightning
- Tornadoes
What is Wind Shear?
- A sudden, drastic change in wind speed and/or direction over a very small area
- Headwind changing to a Tailwind causes loss of aircraft performance
- Low-level is most hazardous due to proximity to ground
- Typically occurs with: Passing frontal systems, Thunderstorms, Temperature
inversions, and Surface obstructions
What is a critical type of shear associated with convective precipitation from a T-storm?
Microburst
What is the typical horizontal diameter of a Micoburst?
- Typically has a horizontal diameter of 1 – 2 miles
What is the typical lifespan of a microburst?
15 minutes
Microbursts produce downdrafts up to _________ feet per minute (FPM)
6000
An Aviation Routine Weather Report, hourly weather observation by a person or
automated equipment is referred to as?
METAR
Information for routine METAR reports is observed between _________ after the
hour until the top of the hour
45 Minutes
METAR is reported between ________ after the hour until the top of the hour
50 Minutes
________ means the report came from an automated source
AUTO
_______ means the report is a corrected observation
COR
__ refers to a CONUS airport
K
METARs report the ___________ visibility, which may differ from the tower visibility or flight visibility.
Prevailing
________ visibility will be reported in the remarks section if it differs from the prevailing visibility and is less than 3 miles.
Sector
Direction the winds are blowing ______ in
degrees from 0 to 360 degrees
from
METAR winds are reported as ________ ___________
True North
A ____ symbol denotes a light intensity level
-
A ___ symbol denotes a heavy intensity level
+
VC indicates a specific weather condition in the ______ of the airport
Vicinity (w/i 5 and 10 statute miles from the reporting station)
In temperature the “M” refers to?
Minus, so M14 would me -14deg C
‘A’ stands for _________
Altimeter
Use altimeter data to calculate what?
Pressure Altitude for Performance Data
A Terminal Aerodrome Forecast (TAF) is a?
Concise statement of the expected meteorological conditions for a 5 statute mile radius
AMD is an
Amended forecast
Routine TAFs are prepared and filed approximately ______________ prior to scheduled issuance times.
one-half hour
TAFs are scheduled for issuance four times daily, what are they?
0000Z, 0600Z, 1200Z, & 1800Z
Routine TAFs are valid for how long?
24 hours
VRB would indicate?
Variable winds
Forecast visibility greater than 6 statute miles is indicated by _______
P6SM
BR is ______
mist
Obscurations are identified when the prevailing visibility is forecasted to be _____
statute miles or less.
6 SM
When clear skies are forecast what is used?
SKC
Code for wind sheer?
WS
For wind shear, Height is given in hundreds of feet AGL up to and including __________
2,000’ AGL
The ___________ group is used when a rapid change in conditions is expected, usually occurring in less than one hour.
FROM (FM)
The ___________ group is used when a gradual change in conditions is expected over a longer time period, usually two or more hours
Becoming (BECMG) group
(more gradual)
The ______________ group is used for any conditions in wind, visibility, weather, or sky condition which are expected to last for generally less than an
hour at a time.
Temporary (TEMPO)
