10. METEOROLOGY Flashcards
What is a METAR?
Routine aviation weather report to which a TREND forecast may be added.
What is a SPECI?
Special aerodrome weather report issued following a significant change from the previous report. Civil stations do not issue SPECIs because of their half-hourly METAR commitment. An amended SPECI will be indicated by the header SPECI COR.
What is a TAF?
A forecast of conditions and significant changes expected during a specified period, normally up to 9 hours, but may be up to 30 hours, issued every 3 hours until the airfield closes. An amended TAF will be indicated by the header TAF AMD, corrected TAFs will be indicated by TAF COR, cancelled TAFs by CNL after the valid time group.
What is a TREND?
A forecast showing significant changes expected in the 2 hours following a METAR or SPECI.
If you see CAVOK in a weather report or forecast, what would it indicate?
That the following conditions are occurring or are expected to occur simultaneously:
a. Visibility. 10 km or more.
b. Cloud. No cloud below 5000 ft, or below the Minimum Sector Altitude, whichever is the greater. NO CB or TCU at any height.
c. Weather. No significant weather in the vicinity of the aerodrome.
Clouds can be classified basically into the following categories - High, Medium and Low. Give one example of each.
a. High - Cirrus, cirrostratus, cirrocumulus.
b. Medium - Altocumulus, altostratus.
c. Low - Stratus, stratocumulus, cumulus, cumulonimbus.
Note: Low cloud often extends to medium and high – cumulus, cumulonimbus, and nimbostratus.
What are the ideal conditions for the formation of radiation fog?
a. A high relative humidity so that little cooling is required to reach saturation.
b. Little or no cloud so that heat is lost by radiation from the surface.
c. Little wind so that cooling is confined to the surface layers, but sufficient to give some turbulence. A wind of 2-8 kts near surface is most favourable although in practice fog should be expected even if the wind is calm.
How is Advection Fog formed?
Cooling of warm air by movement over colder surface (normally the sea) the surface temperature of which is below the dew point of the moving air.
