Weather Flashcards
METAR TYPES
Normal- scheduled observation taken at the end of each hour
SPECI- observation taken at an unscheduled time due to certain criteria like low visibility, low clouds, frozen precipitation or thunderstorms
VC vs. DSNT on METAR
VC- METAR weather is reported within 5-10 NM of station
DSNT- weather is reported greater than 10 NM from station
TAFs- Terminal Area Forecast
- Issued every 6 hours for a 24 or 30 hr period
- 5 SM from center of airport
METAR reading- BCFG
Patches of fog
METAR reading- BLSN
Blowing snow
METAR reading- +TSRA
Thunderstorm with heavy rain
METAR reading- VV003
Vertical visibility 300 ft
METAR reading- R35L/5000
RVR for runway 35L is 5000’ as seen from cockpit
METAR reading- 350V040
Winds are variable between 350 degrees and 040 degrees
M01/M01
Temp is -1 degree and dew point is -1 degrees.
Meaning Fog (possibly freezing fog) low visibility is expected
AO2
Automated observation with precipitation discrimination sensor.
AO1 cannot detect type of precipitation.
B & E on METAR/TAF
Began & End
BC
Patches
BL
Blowing
BR
Mist
DR
Low Drifting
DS
Dust Storms
DU
Dust
DZ
Drizzle
FC and +FC
FC- Funnel Cloud
+FC- well developed funnel cloud like a tornado or waterspout
FG
Fog
FU
Smoke
FZ
Freezing
GR Hail
Greater than 5 mm in diameter
GS Small Hail/Snow Pellets
Less than 5 mm in diameter
HZ
Haze
IC
Ice Crystals
MI
Shallow
PL
Ice Pellets
PO
Well developed dust/sand whirls
PR
Partial
PY
Spray
RA
Rain
SA
Sand
SG
Snow Grains
SH
Showers
SN
Snow
SQ
Moderate squalls
SS
Sandstorm
TS
Thunderstorm
UP
Unknown Precipitation
VA
Volcanic Ash
VC
In the vicinity of
-
+
P
M
B
E
- Light
+ Heavy
P More than
M Less than
B Began
E Ended
BKN
Broken cloud layer 5/8ths to 7/8ths
CB
Cumulonimbus
CLR
Sky clear at or below 12,000 AGL
FEW
Few cloud layer 0/8ths to 2/8ths
OVC
Overcast cloud layer 8/8ths coverage
SCT
Scattered cloud layer 3/8ths to 4/8ths
SKC
Sky Clear
TCU
Towering Cumulus
AMD
Amended forecast
AUTO
Without human editing
BECMG
BECMG 0002 = becoming from 00 to 02 Zulu
CAVU
Ceiling and visibility unlimited
COR
Correction
DSNT
Distant weather
FM
From - FM 0200 = from 0200 Zulu the weather is reporting the following
FROPA
Frontal Passage
LTG
Lightning
LDG
Landing
M
Minus, below 0, less than
NO
Not Available
NSW
No significant weather
P6SM
Plus 6 SM, greater than or more than
PK WND
Peak Wind
PRESFR/PRESRR
Pressure falling or rising rapidly
PROB40
Probability of 40%
RVRNO
Runway visual range not available
SLP (SLP140)
Sea Level Pressure- add 10 to numbers given
Ex. SLP140 = 1014.0
1013.2 mb is std.
TEMPO
Temporary
TEMPO 0002 = temporarily 00 to 02 Zulu
T02560179
Temperature 25.6, Dew point 17.9
TWR VIS
Tower visibility
V
Varying
VV
Vertical visibility, indefinite ceiling
WS
Wind Shear
WSHFT
Wind Shift
With an altimeter setting of 29.85, what is the lowest usable flight level?
FL185, per 91.121 (b) chart (see 91.121 altimeter settings page)
Stages of a Thunderstorm
- Cumulus- updrafts
- Mature- rain, updrafts/downdrafts, wind shear, hail, turbulence
- Dissipating- all downdrafts
What is needed for a thunderstorm to form?
- Unstable atmosphere - warm column of air rising faster than the std. lapse rate, continuing the raising
- Lifting action- fronts, terrain, thermals
- Moisture
Where does most of weather occur?
Troposphere
What causes weather?
Temperature- Unequal heating of earths atmosphere
Warm air- less dense- allows for more movement
Cold air- more dense- more stable
What stage of a TS would you most likely encounter an anvil top?
Mature stage- Anvil top extends out in front of the direction of the storm. Hail is a possibility below/around an Anvil
If the Anvil top is pointed left, what way is the TS moving? Which way would you try to fly around the storm? How many NM?
- Moving in direction of Anvil (Left)
- Fly upwind at least 20NM
What are the effects and indications of Virga?
- Virga is precipitation falling that evaporates before reaching the ground.
- An indication of downdrafts/microbursts beneath and around the surface. Why? Evaporative cooling- when rain evaporates it cools the air—> colder air/heavier/more dense air slams into the ground
Types of Fog
- Radiation
- Advection
- Upslope
- Freezing
- Precipitation-Induced
- Steam
- Valley
- Ice
Radiation Fog
Calm air, cool nights. Ground cools faster than overlying air, cooling air to its dew point.
Advection Fog
Coast/Horizontal winds. Warm moist air blows over cooler dry land, cooling air to its dew point.
Ex. San Francisco
Upslope Fog
Forms adiabatically. Moist air blows up a slope, cooling to its dew point as it raises.
Precipitation-Induced Fog
Rain falling through cold air evaporates, evaporative cooling leads to saturation.
Steam Fog
Ex. Lakes in cooler seasons
Calm dry air over warmer water conducts temperature. Air becomes moist and then cools quicker than the water to its dew point.
Freezing Fog
Air temps at or below freezing. Moisture in the air freezes and becomes visible.
Valley Fog
Moist soil from previous precipitation. Air becomes moist then cools to dew point.
Ice Fog
Mostly occurs at polar regions or areas of extreme low temps.
What is the significance of the temperature/dewpoint spread?
A temperature/dewpoint spread that equals or close together means the air is nearly 100% saturated.
Ex. Clouds, fog, mist, low visibility
Describe a microburst
A microburst is a powerful downdraft of a column of air (associated with thunderstorms). Once that downdraft reaches the ground, it spreads out in all directions causing a wind change as you fly through. Hazardous to aircraft landing and taking off.
What are the aircraft indications of a microburst?
When flying into a microburst with a headwind- IAS & Climb increases. Once through the headwind, it switches to a tailwind- IAS & Lift decrease causing a stall quickly and low to the ground.
How do you escape a microburst?
Continue straight ahead, max power, Vx climb, monitor airspeed and avoid stalling
What is wind shear?
An abrupt change in wind speed or direction. Can cause turbulence or loss of control.
When can you accumulate ice?
When there is visible moisture and temps are near or below freezing.
What are the different types of ice?
- Clear
- Rime
- Mixed
Clear Ice
Glossy, clear ice formed by slow freezing of super cooled water as it flows over the wings.
- forms between 2 and -10 degrees Celsius
Rime Ice
Rough, milky, opaque ice that instantly freezes. Very rapid freezing of super cooled droplets as they strike the wing.
- Low temps, lesser amounts of liquid water, low velocities, and small droplets form rime ice.
Mixed Ice
Mixed is a combination of clear and rime ice on the same surface.
Induction Icing
Forms around the air inlet of turbine engines and can damage compressor blades.
Structural Icing
Forms on an aircraft’s lift generating surfaces, disrupts smooth airflow, decreases lift and increases drag
What temperature difference between dew point and air temp would result in fog?
5 degrees or less between the two
What does ICE do to a wing?
Changes the shape of the wing, causing airflow to become disrupted.
-Decreases lift and increases drag.
When does FROST occur?
Frost will occur when the collecting surface temperature is at or below the dew point of the air and the dew point is below freezing.
What weather is associated with a COLD front and WARM front?
Cold- forms when cooler air displaces warmer air from below, forcing the warm air to rise. — cumuliform clouds, heavy showers, fast moving, thunderstorms. (LOW pressure system)
Warm- forms when a moist, warm air mass slides up and over a cold air mass. — stratiform clouds, low visibility, widespread rain. Can bring gentle rain or light snow, followed by warmer/mild weather. (HIGH pressure system)
‼️‼️ How are Lenticular clouds formed?
“Ocean Waves” above a mountain top- Winds at the top of a cloud layer are moving faster than the layer below.
-They form when moisture is being transported over the top of a mountain in a stable layer of atmosphere.
-Indicative of turbulence and wind shear
In standard atmosphere, what is the speed of sound?
741.4 MPH
Thunderstorms should be avoided by how many miles?
20 miles
How long is a TAF valid for? How many times/day is it released?
24 or 30 hrs
Released 4 times a day. 00z, 06z, 12z, 18z
When is filing an alternate required? What weather must your alternate have?
1-2-3 rule: 1 hr before or after ETA, WX must be 2000 ft ceilings and 3 SM visibility. If not, then an alternate is required.
Alternate must have weather (800/2) for non-precision & (600/2) for precision.
What risks are associated with Thunderstorms and how do you avoid them?
Microbursts and hail.
How long can a microburst last for and how many miles can they take up?
Around 15 min from the time it strikes the ground until dissipation.
Horizontal winds continue to increase during the first 5 min with max winds lasting 2-4 min in a 2.5 mile radius.
On a TAF if there is a TEMPO line what weather does it resort back to after tempo is over?
The main line before the tempo.
What fronts are associated with a microburst?
Cold front
Can you overfly a thunderstorm?
Never plan to. But yes, suggested 1000ft for every 10 kts of movement.
TEMPO- what does it mean to us?
TEMPO change in wx, expected to last less than an hour at any given time.
Occurs during a total or less than half the time period of the TAF.
What is a mountain wave?
Oscillations of wind perpendicular to the ridge of the mountain. Can cause loss of altitude, airspeed fluctuations and turbulence.
