Weather Flashcards
Temperature Inversion
Warm air on top of cold air.
Fog, haze, low clouds, poor visibility, but smooth air.
Moist Unstable Air
Turbulence, showery precipitation (because the air is unstable.
Stable Air
Smooth air, poor visibility, and steady (not showery) precipitation (because stable air is usually humid).
Unstable Air
Intermittent precipitation
Cool + Dry
Stable
Hot + Humid
Unstable
High Density Altitude
Just means “High Altitude”.
Air is thinner, so lift is decreased.
Nimbus
Rain Cloud
METAR Reports
A format for reporting weather information.
METAR
Type of report
hourly or special unscheduled
KABC
Station Identifier (four alphabetic characters)
121755Z
Date/Time
(universal time clock with 24 hour clock)
Two digit date
Four digit time
Always appended with a Z
AUTO
Report modifier
21016G24KT 180V240
Wind direction and speed
210 (direction in tens of degrees)
16 (speed in whole knots)
G24KT (Gusts follows by maximum speed-appended by KT to indicate knots)
180V240 (added only if direction varies by 60 degrees or more with a V representing Variable wind direction.
2SM
Visibility
Prevailing visibility in statute miles and fractions (with a space between whole miles and fractions)
R11/P6000FT
Runway Visual Range
R11 (RVR in hundred of feet)
P6000FT (reported if prevailing visibility is ≤ one mile or RVR ≤ 6000 feet)
Always appended with FT to indicate feet.
Value prefixed with M or P to indicate value is lower or higher than RVR value.
BKN015 OVC025
Sky Conditions
(Cloud amount and height) BKN015 CLR- no clouds detected below 12000ft FEW- a few clouds SCT- scattered clouds BKN- broken clouds OVC- overcast Followed by three digit height in hundreds of feet
(Vertical Visibility) VV followed by height for indefinite ceiling
06/04
Temperature/Dew Point
Each is reported in whole degrees Celsius using two digits
Subzero values are prefixed with a M for minus
A2990
Altimeter
Always prefixed with an A indicating inches of Mercury
Reported using four digits (tens, units, tenths, hundredths)
18004KT
Wind is 180 degree at 4 Knots.
The first three digits (180) are the compass heading.
The last two digits are the wind speed.
Compass Headings
Are always relative to True North in print, not magnetic north.
If it’s in print It is True North
OVC007
Sky is overcast at 700 feet.
Remember #’s are always in hundreds.
1 1/2SM
Visibility is 1 1/2 statute miles SM
BLPY
Blowing Spray
BR
Mist
DS
Dust Storm
DU
Widespread Dust
DZ
Drizzle
FC
Funnel Cloud
+FC
Tornado / Water Spout
FG
Fog
FU
Smoke
GR
Hail
GS
Small Hail / Snow Pellets
HZ
Haze
IC
Ice Crystals
PL
Ice Pellets
PO
Dust / Sand Whirls
RA
Rain
SA
Sand
SG
Snow Grains
SN
Snow
SQ
Squall
SS
Sandstorm
UP
Unknown Precipitation
VA
Volcanic Ash
During the life cycle of a thunderstorm, which stage is characterized predominantly by downdrafts?
Dissipating
Clouds, fog, or dew will always form when?
Water vapor condenses or sublimates on condensation nuclei, liquid or ice particles began to grow.
A no frontal, narrow band of active thunderstorms that often develop ahead of a cold front is known as a…
A squall Line
Which weather phenomenon is always associated with a thunderstorm?
Lightning and thunder
A local storm invariably produced by a cumulonimbus cloud, and is always accompanied by lightning and thunder.
What will a convective SIGMET be issued for?
The forecast may be issued for severe thunderstorms due to:
- Surface winds greater than 50 knots
- Hail at the surface grater than 3/4” diameter
- Tornados, embedded thunderstorms, lines of thunderstorms
ASOS is designed to support?
Aviation operations and weather forecast by providing continuous observations. The ASOS is used to generate a METAR.
Every physical process of weather is accompanied by or the result of?
Unequal heating of the Earths surface
What are the characteristics of stable air?
Characteristics of a stable air mass include:
- Stratiform clouds and fog
- Continuous precipitation
- Smooth air
- Fair to Poor visibility in haze and smoke
What measurement can be used to determine the stability of the atmosphere?
The difference between the existing lapse rate of a given mass of air and the adiabatic rates of cooling in upward moving air determines if the air is stable or unstable.
What area would a remote PIC expect to find the highest amount of thermal currents in normal conditions?
Thermals will occur in Dry Areas rather than moist areas (including woods or forests which hold large amounts of moisture in the foliage)
With a strong steady wind, what would be a concern?
Flight in turbulent conditions may:
- Consume more power to maintain position of sUAS
- Performance may no be adequate to counter wind making it impossible to recover the sUAS
What is the expected duration of an individual microburst?
A Microburst will seldom last longer than 15 minutes
In which situation is Advection Fog most likely to form?
When moist air moves over colder ground or water.
This type of fog is common along coastal areas.
What conditions are necessary for the formation of thunderstorms?
The air must have:
- Sufficient water vapor
- An unstable lapse rate
- An initial upward boost (Lifting) to start the storm process in motion
What is considered the MOST hazardous condition when flying an sUAS in the vicinity of thunderstorms?
Lightning
What would decrease the stability of an air mass?
Surface heating, cooling aloft, converging or upslope winds, or an invading mass of colder air may lead to instability and cumuliform clouds.
The development of thermals depends upon?
Thermals are updrafts in convective currents dependent on solar heating.
A temperature inversion results in?
Stable air with little, if any convective activity.
What weather provides the best flying conditions?
Cool, Dry air is very stable and resists vertical movement, which leads to good clear weather
What is the standard temperature value for sea level?
15°C
What is the standard pressure value for sea level?
29.92 “Hg
