Weather information
.docxWeather information
Information will include air temperatures, winds, pressure patterns, the extent and base of any cloud, and the possibility of fog, icing, thunderstorms or other weather phenomena,
Weather information available to pilots falls into two categories :
1)forecasts of expected weather over an area or region, and at aerodromes;
2)reports of actual weather.
Significant weather that may affect the safety of flight operations may be advised in the form of a SIGMET.
AIRMET Area Forecasts are text based.
Special Forecasts
the pilot can request a forecast office to prepare a Special Forecast specifically for his flight Ibis takes time and at least 2 hours’ notice is required (4 hours’ if the route distance exceeds 500 nm).
Aerodrome Forecasts (TAFs) – terminal aerodrome forecast
Aerodrome Forecasts, known as TAFs, are text messages which follow the international (ICAO) format for aerodromes where observations are taken.
TAFs describe the forecast prevailing conditions at an aerodrome and usually cover periods of 9 to 24 hours.
Aviation weather reports
Aerodrome Weather Reports (METARs on a routine basis and SPECIs when special conditions happen);
Automatic Terminal Information Service (ATIS);
In flight Weather Reports (obtained in a recorded form on a VOLMET VHF frequency, e.g. London VOLMET on 128,6 or 126,6 MHz, or from an ATIS, or by radio communication with an Air Traffic Unit.
Trends (or Landing Forecasts)
It is common to attach a forecast TREND to an Aerodrome Report (i.e. an observation of actual weather) in order to improve the meteorological information.
Information is also obtained from the Automatic Terminal Information Service (ATIS) a tape-recorded message of the current aerodrome information and is broadcast on appropriate VOR or VHF frequencies to off load the АТС communication frequencies.
Some aerodromes have both an arrival and departure ATIS.
CLOUDS
The amount of cloud coverage in Area Forecasts (and in TAFs and METARs) is expressed in eights of the sky covered, or oktas.
КС - Sky clear (0 okta)
FEW - Few (1-2 oktas)
SCT - Scattered (3 ~4 oktas)
BKN - Broken (5 - 7 oktas)
ОVC - Overcast (8 oktas)
TEMPO, Temporary variation lasting less than 60 minutes, or lasting in total less than half the TREND (or TAF) period; that is, changes take place quite infrequently for the prevailing conditions.
Note: TEMPO can relate to improvements as / well as deteriorations in wind, visibility, weather or cloud.
NOSIG: no significant change, NSC : no significant cloud, and NSW: no significant weather.
PROB (probability) percentage.
BECM-becoming NSC – nil significant cloud
BR-mist NSW – nil significant weather
CAT- clear air turbulence RA - rain
DP – dewpoint temperature TS - thunderstorm
FG – fog
IR – ice on runway
NC – no change