Met Flashcards
(26 cards)
What are the conditions associated with a bomb weather low?
Storm force winds
Very low cloud
Extermely poor vis
Storm surges on exposed coasts
Describe a col
A region of light and variable winds
Moisture fed into the col may form thunderstorms in summer or fog in winter
Cloud Amounts in the Sky?
SKC - 0/8 NSC - Less than 3 and/or bases higher than 10k AMSL FEW 1-2/8 SCT 3-4/8 BKN 5-7/8 OVC 8/8
Convective cloud descriptors TCU/CB
ISOL - up to 50%
OCNL - greater than 50, less than 75%
FRQ - more than 75%
EMBD - Embedded in other layers of cloud
What are sigmets issued for?
How long are they valid for?
What are the descriptors?
Thunderstorms TC Turbulence Icing Mountain Waves Sand/Dust Storms Volcanic Ash/activity
4 hours
NTSF - Intensifying
WKN - Weakening
NC - No change in intensity
TAF?
Terminal Aerodrome Forecast within 8km of aerodrome Domestic 12hrs International 24hrs AGL Wind true
TREND?
Trend FORECAST
Appended to METAR/AUTO/SPECI
From AK, WN, CH, OH, WP only
Short term forecasts, valid for 2 hours
Takes precedence over the TAF
True wind
METARs are only issued from?
WP, OH, Milford Sound
SPECI?
WP, OH, Milford Sound only
Usually issued off the hour if significant wind change or cloud base reduces to 1500ft or vis reduces to 800m or less
CAVOK?
Vis 10km or greater
No CBor TCU at any height
No cloud below 5k or highest min sector altitude
AA/WN/CH
NO SIG?
No significant change - nsc expected to occur within the 2 hour period of the trend
TEMPO?
Temporary changes each lasting less than 60 mins where temporary conditions are less dominant than original forecast conditions
WS in TAF?
Wind shear
Fog/Mist/Haze Visibilities?
Fog less than 1000m
Mist 1000-5000m
Haze less than 5000m - contaminant is not water
Which layer of the atmosphere do we find weather?
Troposphere
Average height of 36090 ft
Higher in areas with more thermal heat from the sun
Isothermal at -55deg from tropopause
Average environmental lapse rate?
-2deg/1000ft
How is latent heat caused? What does it do?
When water vapour changes from gaseous to liquid or solid, it releases latent heat - this heat release destabilises the atmosphere
ISA conditions?
MSL Temp 15deg
MSL Pressure 1013.25
MSL Density 1.225kgm3
Temp lapse rate 1.98 deg per 1000ft up to 36090, then -56.5
What is albedo?
A measure of the amount of incident radiation that is reflected
Snow =80%
Forest =5-10%
Radiation inversion?
Overnight in clear sky conditions
Earth loses heat and cools down
A relatively cool layer of air, usually adjacent to a ground surface cooled by net loss ofradiation, in which theair temperatureincreases with height
Can form radiation fog or mist
Subsidence Inversion?
Dry and warming subsiding air, sinking onto an area of weak convection
Effects of an inversion?
Formation of SC cloud
Reduced visibility
Light mechanical turbulence
Wind shear
Define QNH
Aerodrome level pressure corrected to MSL
Altitude above MSL
QFE?
Aerodrome level pressure set on the altimeter
Height above aerodrome
