Weather information

Weather 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