Weather Flashcards
DESCRIBE Troposphere
- layer adjacent to earth’s surface
- average height over US is 36,000 ft
- temperature decreases with alt.
- nearly all weather occurs here
- winds generally light but increase with alt.
- winds over 200 kts at top
DESCRIBE Tropopause
- transition zone between troposphere and stratosphere
- isothermal
- jet stream just below
- mod. to sev. turb. from jet stream
- contrails or haze layer persist
- average height of 36,000 ft over US
- anvil tops of Tstorms spread out here
DESCRIBE Stratosphere
- increasing temperature with inc. alt.
- caused by ozone
- generally smooth with exc. vis.
- air is thin
- general lack of weather
DESCRIBE flight conditions of troposphere
- winds light to 200+ kts closer to jet stream
- all weather occurs here
DESCRIBE flight conditions of tropopause
- an infinitely thin region, cannot fly “in”
- jet stream produces mod. to sev. turbulence and wind shear
- haze and contrails persist
DESCRIBE flight conditions of stratosphere
- smooth and exc. vis
- little resistance
- lack of weather
- hard to reach for many planes
DEFINE Lapse Rate
decrease in atmos. temp. with inc. alt.
STATE average lapse rate in dg C
2 dg C
DEFINE atmospheric pressure
pressure exerted on a surface by the atmos. due to the weight of the column of air directly above that surface
STATE standard units of pressure
inches of Mercury (in-Hg or “Hg)
millibars (mb)
DEFINE standard atmosphere
a hypothetical vertical distribution of the atmos. temp., pressure, and density… which by international agreement is considered to be representative of the atmos. for pressure-altimeter calibrations and other purposes
DIFFERENTIATE between sea level and station pressure
SLP is measured from the existing weather if the station were at MSL while station pressure is the atmos. pressure measured directly at an airfield
DEFINE types of altitudes
Altitude: height above a given ref.
Indicated: altitude read directly from the altimeter
Calibrated: indicated corrected for instrument error
MSL/True: actual height above MSL / correcting calibrated for temp. deviations
AGL/absolute: a/c’s height above the terrain directly beneath the a/c
Pressure: height above the standard datum plane
DEFINE Indicated Altitiude
altitude read directly from the altimeter
DESCRIBE effects of pressure changes on aircraft altimeters
High to Low, look out below
Low to High, plenty of sky
DESCRIBE effects of temperature deviations from standard lapse rate on aircraft altimeters
High to Low, look out below
Low to High, plenty of sky
EXPLAIN pressure gradient
rate of pressure change in a direction perpendicular to the isobars
EXPLAIN and IDENTIFY gradient winds and Buys Ballot’s Law (N Hemisphere)
- winds resulting from PGF and Coriolis that circulate CW around highs and CCW around lows
- found above 2,000 ft AGL
- BBL: wind at back, L is to left
EXPLAIN and IDENTIFY surface wind direction (N Hemisphere)
- found below 2,000 ft AGL
- surface friction lessons Coriolis force and winds flow 45 dg across isobars
- 45 dg across isobars and into low in CCW
- 45 dg across isobars and out of high in CW
DESCRIBE jet stream
narrow band of strong winds of 50 kts+ that meanders vertically and horizontally around the hemi. in wave-like patterns
DESCRIBE sea breeze
-during the day, winds that come from the colder sea to warmer land at 15-20 kts
DESCRIBE land breeze
- at night, winds that come from the colder land to warmer sea
- slower than sea breeze
DESCRIBE mountain winds
-at night, winds that come from cooler mountains to warmer valley in circular process
DESCRIBE valley winds
-during the day, winds that come form cooler valleys to warmer mountains in circular process
DEFINE saturation
maximum amount of water vapor that air can hold for that temperature
DEFINE dew point temperature
temperature at which saturation occurs
DEFINE dew point depression
-the difference between temperature and dew point temperature: DPD=T-T_D
DEFINE relative humidity
percent saturation of the air
DESCRIBE relationship btwn air temp and dew point temp
- the closer they are, the more wet things get
- at 4 dg difference, fog and clouds
- precipitation at 0 dg diff
- higher the dew point temp, the more moisture
DESCRIBE 3 characteristics of precipitation
- Continous: (steady) intensity changes gradually if at all (stratiform)
- Showers: sudden beginning or ending, abruptly changing intensity (cumuliform clouds)
- Intermittent: stops and restarts at least once during the hour (either showery/steady and cumuliform/stratus)
DESCRIBE types of precipitation
- Drizzle: lqd or frz (on impact)
- Rain: lqd or frz (on impact)
- Hail/Graupel: ice chunks circulated and accreted in Tstorm
- Ice pellets/sleet: rain falling through freezing air
- Snow: accretion of ice crystals (condensation at below frzng)
- Snow grains: small opaque grains of ice
DESCRIBE four principal cloud groups
Low: SFC-6500
Middle: 6500-20000
High: above 20000
Special: extensive vertical dev.
DESCRIBE weather conditions assoc. with cloud groups
Low: hide terrain or Tstorms, icing, turbulence, light RN/DZ, low vis
Middle: low-mod vis, none-mod icing, none-mod turb.
High: good-fair vis, none-light icing, none to light turb
Special: low vis, severe icing, severe turb
DESCRIBE types of atmos. stability.
Stable: air pushed up returns
Unstable: air pushed up and continues to rise
Neutral: air pushed up stays
DESCRIBE 4 methods of lifting
Frontal: cold fronts lift air ahead
Orographic: force of wind agnst Mt. pushes air upward
Convergence: force air upward when air masses collide
Thermal: (convective), air heated by warm surface rises
DESCRIBE flight conditions assoc. w/ stable atmos.
F-Warm A-Warm T-Smooth V-Poor I-Rime P-Steady W-Steady C-Stratus
DESCRIBE flight conditions assoc. w/ unstable atmos.
F-Cold A-Cold T-Rough V-Good (out of clouds) I-Clear P-Showery W-Gusty C-Cumulus
DEFINE air mass
-large body of air that has essentially uniform temp and mositure conditions in a horizontal plane
-named for location, moisture content, and temp:
TAPE MC WC
DEFINE front
an area of discontinuity that forms btwn two contrasting adjacent air masses
DESCRIBE structure of a front
- A 3D boundary between contrasting airmasses
- cold typically steeper and \ in a curve if moving >
- warm typically shallower and / if moving >
- move perpendicular to lines on map
- cold moves faster than warm
- located in trough of L
DESCRIBE discontinuities used to locate and classify fronts
- wind shift
- temp/dew point discont.
- moist. discont.
- pressure swing
DESCRIBE factors that influence frontal weather
- Moisture
- Contrast
- Stability
- Slope
- Speed
DESCRIBE conditions assoc. w/ cold front
- overtaking air is dense and cold
- frontal lifting => unstable
- cooler temps and clearing skies after
- narrow front
- SE at 20
- winds SW to NW
- cumuliform
- rough turb
- blue
DESCRIBE conditions assoc. w/ warm front
- W air advances over dense cold air
- extensive forward slope
- wx ahead of sfc front
- steady precip and reduced vis
- winds SE to SW
- NE at 15
- stratiform
- smooth turb
- red
DESCRIBE characteristics of a squall line
- line of sev. Tstorms
- 50-300 mi. ahead of CF
- sometimes w/o CF
- servere hazard
DESCRIBE conditions assoc. w/ stationary front
- C and W front mix symbol
- wx like mild WF
- aligns any dir.
- 180 dg WS
- no movement
- stratiform
- smooth turb
DESCRIBE conditions assoc. w/ occluded fronts
- C overtakes W
- Purple
- C/W depending on which stays at SFC
- SE to NW
- NE at 15-20
- comb. of clouds and turb.
DESCRIBE conditions assoc. w/ inactive front
- dry fronts
- no clouds/precip
- wind and temp shift still
- potentially unfavorable flying
LIST class. of turb
FMLT Frontal Mechanical Large Scale WS Thermal
LIST intensities or turb
Light
Moderate
Severe Extreme
DEFINE turb. time terms
Occasional: less than 1/3
Intermittent: 1/3-2/3
Continuous: more than 2/3
DESCRIBE thermal turb. development
caused by localized vertical cenvective currents resulting from surface heating (or C air moving over W ground)
DESCRIBE mech. turb. development
results from wind flowing over or around irregular terrain/obstructions
DESCRIBE cloud formations assoc. w/ mountain waves
Cap: obscures mountain top on both sides
Lenticular: forms 20000+ ft, cylindrical and smooth, but signify turb.
Rotor: about same height as mt.
DESCRIBE techniques for flight in vicinity of mtn. waves
1) fly around
2) fly 50% higher
3) avoud CLR clouds
4) approach at 45 dg angle for quick escape
5) avoid leeward side of mt. (downdrafts)
6) don’t trust altimeter as much
7) recommended turb. penetration speed
DESCRIBE how frontal lifting creates turb.
lifting of W air by front leads to instability, worst in fast moving CF
DESCRIBE how temp. inversions are ex. of WS turb.
turb at boundary between inversion layer and surrounding atmos, wind moving in different directions
DESCRIBE how jet streams are ex. of WS turb.
rapid wind speed change in short distance
DESCRIBE recommended procedures for flying thru turb.
1) turb. air penetration speeds
2) trim for level flight
3) control attitude without abrupt changes
4) let A/S and altitude drift
DESCRIBE structural icing
icing that forms on external surface of an aircraft
STATE requirements for form. of struct. icing
1) super cooled visible water
2) free air temp and skin must be below freezing
STATE temp range most conductive to struct. icing
0 to -20 dg C
DESCRIBE icing conditions assoc. w/ fronts
- CF and SL have narrow band of rapid clear icing
- WF and SF have wider band of slow rime icing
- OF have widespread icing, rapid, all types
IDENTIFY hazards of a/c icing
- decreases: L, T, range
- increases: D, W, fuel use, and stall speed
- vibrations => stress
- engine icing
- pitot-static icing
DESCRIBE types of engine icing
- induction: (inlet) reduced pressure leads to icing when 10 dg C or less and high humidity, can lead to FOD
- compressor: restricts flow and can cause engine flameout, loss of T, rapid rise in exhaust temp
DESCRIBE ground icing hazards
- de-icing fluids are highly corrosive
- can hamper movement of control surfaces
- increase braking distance
IDENTIFY procedures to minimize or avoid icing
- mechanical: deicing boots (inflate)
- fluids: corrosive, must be carefully applied
- heat: electrical/exhaust heating
1) avoid icing areas
2) avoid clouds at 0 to -20 dgC
3) don’t fly through wet precip at/around freezing temps
4) avoud low clouds above mtns
5) no steep turns when iced
6) avoid high AOA when iced
7) greater fuel consumption when iced
8) change alt. to warmer to colder than frzng range
9) climb above frzng rain
10) don’t fly parallel to icing front
11) avoid icing in terminal phase
12) more power on final when iced
13) always remove ice/frost before T/O
LIST intensities of icing
TLMS Trace Light Moderate Severe
LIST types of icing
RCMF Rime Clear Mixed Frost
DEFINE types of vis.
Visibility: ability to see and identify prominent unlighted objects by day and lighted objects at night
Flight: avg fwd horizontal distance
Prevailing: greatest hor. vis equaled or exceeded throughout at least half of circle
Slant Range: distance on final appch when rwy environtment is insight
Runway Visual Range (RVR): hor. distance (100s feet/meters) a pilot will see by looking down the runway from approach end
DEFINE obscuring phenomena
any collection of particles that reduce hor. vis to less than 6 miles
DESCRIBE sky coverage terms that define ceiling
ceiling: height AGL ascribed to lowest BKN or OVC layer or vertical vis. into an obscruing phenomenon (VV)
BKN: 5/8-7/8 sky cover
OVC: 8/8
VV: 8/8 surface based vis into obscuring phen.
DESCRIBE parameters that define fog
Fog: visible aggregate of minute water droplets that:
1) is based at/within 50 ft of SFC
2) greater than 20 ft in depth
3) reduces prevailing vis. to less than 5/8 SM
STATE req. for fog formation
1) Condensation nuclei
2) high water content/ low DPD
3) light SFC winds
DESCRIBE two main types of fog
advection: warm moist air moves over cold sfc (Western coastal areas esp.), persists for long time and generally blows back and forth
radiation: caused by nocturnal cooling on clear nights, afternoon-sunrise, dissipated by wind or solar heating
DESCRIBE av. hazards of ash clouds
- engine malfunctions
- engine flameout
- pitted windscreens
- sandblasting of skin
DESCRIBE Tstorm hazards
Hail: 3/4 inch Icing Microburst Extreme Turb: GF 5-20 nm ahead, roll/wall clouds Lightning Tornado
DECRIBE Microburst signs and hazards
signs: RADAR, cumuliform clouds, diverging rain, virga, localized blowing dust, roll clouds, vivid lightning/tornado
hazards: downdraft of 2-6k ft/min, 20-200 kt winds
EXPLAIN how radar can aid pilot near Tstorm
NEXRAD: accurately track, determine wind intensity/speed as well as likelihood of a/c icing and turb. intensity
Airborne RADAR: can circumnavigate Tstorms, not penetrate since hail and CAT can be found in between
DESCRIBE recommended techniques for avoiding Tstorm hazards
1) Circumnavigate
2) Over: 1000 ft/10 kts wind
3) Under: 1/3 up from ground to cloud base
4) Through: lower 1/3 since better weather (4-6k ft)
DESCRIBE use of METARs in flight planning
- determine existing weather at destination or alternate
- whether field is operating under IFR or VFR
- determine weather trends by checking last several METARs
- provide comparison btwn observed and forecast wx
INTERPRET weather conditions from a METAR
Type Station ID Time Report Mod. Wind: 3 digit course and 2 digit wind speed, G for gust Vis: in SM RVR: RWY # and RVR in feet Present WX: BR, RN, etc. Sky Condition: Cover and alt. Temp/Dewpoint Altimeter Remarks
BR = mist FG = fog FU = smoke HZ = haze GR/GS = hail RA = rain DZ = Drizzle
DESCRIBE use of TAFs for flight planning
- determine IFR/VFR
- type of approach required
- determining if alt. field required
- forecasting weather for specific field
DESCRIBE difference in US civil, military, and intl TAFs
US Mil: 24 hr, knots, no CAVOK, vis in meters
Intl: variable time, knots/mph/kph, CAVOK, vis in meters
Civilian: date/time prepared and issued, two digit date, vis in SM, probability of precip.
INTERPRET forecast weather from TAF
TAF Station Time Wind Vis Weather/Obstructions Altimeter Sky Conditions Change Groups: FM, BECMG, TEMPO
DESCRIBE use of Surf. Analysis Charts (SAC)
depicts current pressure centers, fronts, and barometric pressure lines
INTERPRET SACs
-isobars at 4 mb intervals, displays, H, L, and fronts
DESCRIBE Low Level Sign. Wx Prognostic Chart
-depict predicted positions of fronts and pressure centers as well as forecast wx across the country
DESCRIBE displayed data METARs
- visual representation of METARs all over area
- determine areas of IFR/VFR
- minimum ceiling en route
DESCRIBE wx data on NEXRAD
- compliation of radar data
- precipitation and intensity by return in db
- areas of tornadoes, hail, wind shear, and microbursts
DESCRIBE wx data on satellite imagery
- type and height of clouds
- temp and thickness of cloud layers
- ground temp
- general cloud coverage
DESCRIBE use of Winds-Aloft Prognostic Charts
- observed and average forecast flight level winds aloft
- direction and speed
- temp aloft
DESCRIBE use of winds-aloft forecast
- 2 digit heading, 2 digit speed +/- 2 digit C temp
- temp assumed - above 24,000 ft
- 99 direction means variable
- dir > 360 are for 100 kts plus, found by subtracting 50 (500) from direction and adding 100 to kts, 99 if above 200 kts
- no wind within 1500 ft AGL
- no temp within 2500 ft AGL
- no temp at 3000 ft level
DESCRIBE the use of Severe WX Watch Messages
- issued as needed by progress and dev. of severe wx
- includes alert for immintent watch message
DESCRIBE use of in-flight wx advisories
- includes SIGMETs, convective SIGMETs, and AIRMETs
- SIGMETs: severe+ turb, non Tstorm CAT, non Tstorm severe icing, widespread dust storms or sandstorms, volcanic reuption and ash clouds
- Convective SIGMETs: tornadoes, lines of Tstorms, embedded Tstorms, Large (VIP LEVEL 4) Tstorms, Hail 3/4”+, wind gusts 50 kts+
- AIRMETs: Sierra (IFR, mountain obscuration), Tango (mod turb or sustained SFC winds of 30 kts+), Zulu (mod. icing or freezing lvl data)
DESCRIBE use of PIREPs
- given to ATC or other weather stations
- pilot observed wx
- ATC required for ceilings below 5000 ft, vis = 5mi, Tstorms, icing light+, turb mod+, and WS
- cloud bases, tops, and layers
- flight vis
- precip
- vis restrictions
- winds at alt
- temps aloft
- unusual/unforecast wx
- on IFR approach when different from forecast
- missed approach bc of wx
- WS on arrival/departure
DESCRIBE wx data entered on DD form 175-1
- temp/dewpoint
- temp dev. from lapse rate
- pressure and density alts.
- SFC winds
- climb winds
- wx warnings/advisories
- latest RSC or RCR
- T/O affecting wx
- FL winds and temps
- space wx
- clouds/ vis restrictions
- minumum ceiling, max cloud tops, aand min freezing level
- Tstorms, turb., icing, precip
