kap 6- aerodrome weather Flashcards
What is a routine weather report issued regularly called?
METAR (Meteorological Aerodrome Report)
What is a SPECI?
A SPECI is a special weather report that contains the same information as METAR, and becomes issued when conditions change quickly over a short time period.
Elements of METAR/SPECI
a. identification of type of report
b. location indicator
c. time of observation
d. surface wind direction and speed
e. visibility
f. RVR, when applicable
g. present weather
h. cloud amount, type (only for CB and TCU at or near the airport) and height of base
i. air temperature and dew-point temperature (included in routine and selected special reports)
j. pressure values, i.e. QNH/QFE
k. supplementary information (warning, landing rwy, runway condition)
How is wind reported when directional variations occur?
When directional variations are to be reported, the two extreme directions between which the wind has varied should be reported in degrees, for example “VRB BTN 350 and 050 degrees”
How does wind from 277 degrees look like in a METAR
280 degrees (rounded to the nearest 10)
How are variations from mean wind speed reported in METAR?
They should be reported as the maximum and minimum values, eg. “MAX35 MIN10”
What does CALM mean in METAR?
Wind is less than 1 kt (2km/t)
What does VRB mean?
VRB (variable) means that the wind is less than 3 kt and variation in the wind directions (60 degrees or more). It is also used when wind direction is variable of 180 degrees or more, and the windspeed is 3 kt or more (variable).
What happens when the wind direction is variable between 60 and 180 degrees, and the wind speed is 3 kt or more the wind shall be given in what way?
E.g. 09014G26T 360V170
for wind between 360 and 170 degrees, and mean wind at 90 degrees.
What shall be marked in reports disseminated beyond the aerodrome in regards to the wind?
a. variations from the mean wind direction should be given if the total variation is 60 degrees or more with mean speeds above 2 kt
b. maximum wind speed should be included only if it exceeds the mean speed by 10 kt or more
c. minimum wind speed should not be given
How is horizontal visibility measured?
It is measured by reference to objects whose distance from the point of observation is known. For take-off reports the visibility observations should be representative of the take-off and the climb out area, and for landing reports the observations should be representative of the approach and landing area.
How is visibility reporting abbreviated in weather reports such as METARs?
Visibility;
- less than 500m = in steps of 50 m (VIS 350M)
- 500 m or more but less than 5 km = in steps of 100 m
- 5 km or more but less than 10 km = in kilometer (VIS 7KM)
- 10 km or more = should be given as 10KM, except for CAVOK
What does “prevailing visibility” mean?
Used in METAR and SPECI. It is observed visibility which is reached or exceeded within at least 50 % of the horizon circle or the dominant visibility of at least half of the aerodrome surface.
What types of weather phenomena should be reported?
- Drizzle (DZ)
- Rain (RA)
- Snow (SN)
- Snow grains (SG)
- Ice crystals (IC)
- Hail (GR)
- Small hail (GS)
- Mist (BR)
- Fog (FG)
What are lithometeors?
Conglomeration of small solid particles (such as dust and sand) that are suspended in the atmosphere and often produce a dry haze.
