The ATIS is a system that broadcasts aerodrome information over the radio. This includes (but is not limited to) aerodrome name, time of the ATIS observation, runway in use, surface wind, visibility, weather, cloud, temperature, dew point, QNH etc.
A pilot is expected to receive the ATIS before departure and when approaching an aerodrome for landing. However, not all airfields will have an ATIS – some of the smaller ones will pass the airfield information to you over the radio instead. You can find out if an aerodrome has an ATIS by looking at the aerodrome’s entry in the AIP.
METARs, landing forecasts, SIGMETs, and any forecast trends for the next two hours are broadcast over the radio on a continuous loop, read by an automated voice. This service is called VOLMET and there are specified VOLMET frequencies across the world, which can be found in each country’s AIP. In the UK & Ireland, these are split into:
London Main – 135.375
London North – 126.600
London South – 128.600
Dublin – 127.005
Scottish – 125.725
Significant Meteorological Information (SIGMET) is published for each Flight Information Region (FIR) by the meteorological watch office in each country (in the UK this is the MetOffice). They are notices of weather that may be hazardous to aviation. These are available online and should be checked before flight.
SIGMETs are also passed to aircraft in flight via the radio when necessary. This includes any of the following occurring or being expected in the next 500nm or 2 hours flying time:
An example SIGMET:
EGTT SIGMET 03 VALID 161130/161500 EGRR- EGTT LONDON FIR SEV MTW FCST WI N5500 W00048 – N5400 W00030 – N5400 W00300 – N5500 W00413 – N5500 W00048 FL070/240 STNR NC=
161130/161500: Valid from 16th day at 1130Z until 16th day at 1500Z
LONDON FIR: Issued for the London Flight Information Region
SEV MTW: Severe mountain wave forecast
FCST WI: Forecast within, then followed by coordinates which form a box of the forecast area
FL070/240: Forecast from Flight Level 70 up to Flight Level 240 (7,000ft to 24,000ft on the standard pressure setting)
NC: No change