Weather Flashcards
Standard temp at sea level. Lapse rate?
15C
2C/1000 feet
Jet stream
Winds > 50 knots; in the troposhere; moves south/increases velocity in winter (IRTP 1-4)
Air circulation in Northern Hemisphere around high press system:
clockwise around high pressure
Coriolis force
right angle to wind; deflects wind to the right in North Hem
Unstable vs stable air
Unstable: cumuliform clouds, showery, turbulence, clear
Stable: stratiform clouds, continuous precip, smooth, poor vis
un=CSTC (unstable cats see thru clouds)
Cloud types
high clouds: cirrus, cirrocumulus, cirrostratus - ice crystals
unstable: cumulus
prefix “nimbus” means raincloud
lenticular clouds: lens shaped, near mountians, very turbulent
Three stages of thunderstorm development?
cumulus (updrafts)
mature (rain)
dissipating (downdrafts)
Most hazardous types of thunderstorm (2)?
1) Squall-line thunderstorms; develop ahead of cold front
2) Embedded thunderstorms
What to do if you enter a thunderstorm?
Eyes on instruments, reduce power, ride the waves, don’t turnback
Conditions for ice formation?
Aerodynamic cooling?
Visual moisture and temp < 0C
Can lower temp in airfoil even if temp is >0
Types of icing?
Rime: small droplets immediately freeze on surface, forms on leading edges, milky appearance (from air bubbles), most common, associated with stratus/smooth air
Clear: from larger droplets or freezing rain, most dangerous, hard to see, very rapid, very rare
Mixed: characteristics of both
Two other types of icing?
Structural: ice on exterior, occurs when supercooled water contacts any part of aircraft < freezing
Induction: “affects powerplant operation”
What to do if rain is freezing on impact?
Fly higher
Other considerations with icing: takeoff a/c certified for ice tail power
No takeoff if any ice on aircraft
“roll upset” - severe inflight icing (for planes certd into icing)
tail can collect faster, cause stall, especially when flaps are applied
more power required
ice the thickness of sandpaper
can cause 30% loss of lift, 40% more drag
Wind shear
definition
expect when (3)?
where is it around cold/warm fronts?
change in wind speed or direction
1) strong temp inversion, 2) around TS, (3) near frontal activity
in front of warm, behind cold
TAF & METAR issuing time format
METER date/zulu eg. 091955Z: date=9, zulu=1955
TAF issue/valid time eg. 091730Z 0918/1024
issued on the 9th at 1730Z, valid from 18Z on the 9th, to 24Z on the 10th
layer thickness math from METAR?
if airport elev=1300, metar says BKN008, OVC020?
tops are reported 3800
OVC is 2000+FE = 3300 feet
and 500 feet thick
TAF Qualifiers
cloud amount
FM interpret
FEW > SCT > BKN > OVC (FSBO)
FM091930: beginning of change, eg day=09, zulu=1930
METAR remark
RAE42SNB42
rain ended at 42 min past the hour, snow begin at 42 past the hour
TAF distance and duration
5 mile radius, valid for 24 hours, issued 4 times/day
Area forecast (FA)
size
issuance
several states
3x per day
PIREP format
UA/OV OKC 063064/TM 1522/FL080/TP C172/TA M04/WV 245040/TB LGT/RM IN CLR
over OKC 63deg rad, 64 miles, at 1522Z, 8000 feet, cessna, temp=-4C, wind from 245deg at 40knots, turb is light
Winds aloft decode?
direction, velocity and temp (if >50 knots, then -50 +100; “99” >200)
eg 234502: from 230 true north, 45 knots, temp=2C
eg 734502: from 230 true north, 145knots, temp=2C
eg 739902: from 230, >200 knots, temp=2C
Weather advisories types, freq, max forecast period?
AIRMETS and SIGMENTS, unscheduled and issued when reqd. Issued at 30 intervals, may live for 6 hours
AIRMETS -haz weather that may affect single engine
SIGMENT - all planes
CONVECTIVE SIG - tornadoes, TS, embedded, sev ice, turb
Convective Outlook
Used to plan flights later in the day. Predicts TS in the next 24H
Radar summary chart
Shows only ppt. Only chart that shows size and intensity of TS rating: solid: instense, extreme one ring: strong two rings: weak or mod
Constant Press Chart
Upper air weather shows temp, press, dp, wind, over 12 H period
Sig Weather Prog Chart
shows surface & 24,000 feet at 12 & 24 out
What procedures should you use to land if icing suspected?
more power, higher airspeed, flapless
expect higher stall, longer roll
Microburst
- rapid downdraft from cloud down to the ground where it spreads in directions (think flushing tiolet)
- dissipates after 10-20 min
Thunderstorm - inadvertent penetration
low as possilbe
tighten seatbelts
pitot heat, lights on
slow to man speed
do not turn around (load factor too high)
do not attempt to hold altitude (ride it out)
Icing details (from Everything Explained)
temp +5 to -20C check AIRMET, SIGMETS "slight possibility" = KNOWN icing stay 3000 below or 8000 above freezing level climbing is the first rule for icing (to air too cold for icing); descend is the second option 90% of ice in 3000 feet layer most clouds max at 30,000 land with fast airspeed, no flaps
Freezing rain
indicates warmer air above most severe, very fast appearance forms on sharp surfaces very fast buildup turn around seen close to the ground
TAF
issued
Terminal Aerodrome Forecast
24 hour forecast issued 4x/day
issued at 32 large airports for a 5 mile radius
eg KPIT 091730Z 0918/1024 …..FM091030
day = 9th, 1730Z
valid time = day 09, 18Z to the 10 at 24Z
beginning at day 09, at 10:30Z
TAF abbreviations
VC
- “nothing” or +
VC - vicinity
- light, nothing=moderate, + heavy
SH=showers, DZ=drizzle, BL=blowing, FZ=freezing, BC=patches, MI=shallow, PR= partial, DR=drifting
RA=rain, GR=hail, SN=snow, PL=ice pellets, SG=snow grains, IC=ice crystals, GS=small hail, UP=unknown ppt
BR=mist, FU=smoke, VA=volcanic ash, SQ=squall, DS=dust storm, SS=sand storm, PO=sand whirls, FC=funnel cloud, +FC=tornado
EFAS
Enroute flight advisory service
122.0
AIRMET
zulu
tango
sierra
Wx of interest to all aircraft, especially small 4x per day for a 6 hour forecast zulu - icing and freezing levels tango - turbulance, strong wing sierra - mountain obscuration or IMC
SIGMET
Significant met info
serious Wx include turbulance, icing, smoke, ash
Five types of NOTAMS
(D) NOTAM: (distant); common type, airport info
(FDC) NOTAM: (Flight Data Center); regulatory, eg TFR
AC: Advisory circular
Pointer :military
GPS: must ask if getting briefing
Ice pellets indicate?
Freezing rain above, do not climb
Three phases of TS?
Cumulus: water vapor condenses
Muture: when rain hits the ground
Dissipating: characterized by downdrafts/lightening
Five forecasts types
Area forecast Winds aloft Wx depiction - shows IFR conditions Radar summary - rain and direction Prog chart - 12/24 hours
Ceiling & vis catagories
LIFR 3000 >5
+ and - on meters, eg -SHRA
- –> light
+ –> heavy
types of fog?
radiation (ground): Ground cools air. warm, moist air; cool, calm nights, little wind
advection (sea): Wind pushes warm air over water or gound
upslope: moist air in low dew point conditions
Acro: RAU
