Meteorology

SIGMET AIP GEN 3.5

SIGMET information concerns the occurrence or expected occurrence, in an area over which meteorological watch is being maintained, of one or more of the following:

SIGMETs for TS are only issued when the TS are:

• OBSC by haze or smoke and cannot be readily seen;
• EMBD within cloud layers and cannot be readily recognised;
• FRQ with little or no separation between adjacent clouds and covering more than 75 per cent of the area affected or
• SQL TS, that is, TS along a line of about 100 nm or more in length with little or no separation between clouds.

SIGMETs for TS do not refer to CB, ICE or TURB as their presence is implied.

SIGMETs for TC include reference to the height of CB tops but not to TS, ICE or TURB as their presence is implied.

SIGMETs for MTW are issued when accompanying downdrafts of 600 ft/min or more are estimated.

SIGMET for TURB refers to low-level turbulence associated with strong surface winds, to rotor streaming, or to turbulence near jet streams.

Pilots in command of aircraft encountering any of the above phenomena, not notified by SIGMET advices, must report details of the phenomenon in an AIREP SPECIAL (AIP GEN 3.5).

SIGMETs are issued by MET forecasters and disseminated by ATS as an element of ATC-initiated FIS to aircraft operating on routes or in areas likely to be affected. This information will normally relate to phenomena reported to designated reporting points, and where possible will indicate the area in which the phenomenon exists.

AIRMET

AIRMET information concerns the occurrence, or expected occurrence, in an area over which meteorological watch is being maintained, of one or more of the following phenomena when the phenomena have not been included in a current GAF:

• isolated and occasional thunderstorms
• moderate icing
• moderate turbulence, when this is expected to occur in an area, or at a time, where or when it is not a normal seasonal feature
• extensive areas of visibility of less than 8 km
• extensive areas of cloud coverage of BKN or OVC below 1500 ft above ground level and
• when the wind at lowest-level forecast (for example 2000 ft) is expected to increase by at least 20 kt to at least 40 kt.

AIRMET information, which concerns phenomena of a lesser degree of severity than SIGMET information, is given to aircraft operating at or below 10,000ft.

AIRMET information is issued by MET forecasters and disseminated by ATS as an element of ATC-initiated FIS, to aircraft operating on routes or in areas likely to be affected. It will indicate the locality or area in which the phenomena exist or are expected to exist.

Pilots in command who encounter any of the above phenomena, which have not been notified by a forecast or an AIRMET advice, should report the details by SHORT AIREP.

Hazardous weather

Responsibility AIP GEN 3.5

Cooperative and concerted action is required by pilots, meteorologists and ATS to ensure the most accurate information is promulgated to assist pilots in the avoidance of hazardous weather, particularly volcanic ash clouds and phenomena associated with thunderstorms—icing, hail and turbulence.

Meteorologists are responsible for the observation of weather phenomena and forecasting their occurrence, development and movement, in terms applicable to aircraft operations. These forecasts need to be produced in sufficient time for evasive action to be taken.

ATS is responsible for distributing reports of hazardous meteorological conditions to pilots as a part of the Flight Information Service. ATS also makes visual and limited radar weather observations for the information of meteorologists and pilots, and is responsible for relaying pilot weather reports to the BoM. At some locations, ATS is provided with METRAD or RAPIC which may supplement weather advice by the ATS. Details are given in AIP GEN 3.3.

When manoeuvring in hazardous weather, pilots are responsible for the safety of their own aircraft using advice and clearances passed by ATS and information obtained from their own visual or airborne radar observations.

They are also responsible for passing visual and airborne radar observations of hazardous weather to ATS.

Pilot action

Outside controlled airspace all hazardous weather avoidance action is the sole responsibility of the pilot in command. However, in order to preserve the safety of the aircraft and other air traffic, the pilot in command is requested to advise ATS of intended actions.

The pilot in command, both inside and outside controlled airspace, must advise ATS promptly of any hazardous weather encountered, or observed visually or by radar. Those observations should include as much detail as possible, including location and severity. Hazardous weather includes, in particular, thunderstorms, severe turbulence, hail, icing and line squalls, and volcanic ash cloud.

Wind shear — pilot reporting

Wind shear encountered by aircraft must be reported by pilots to ATS as aircraft following may not have the performance required to recover from the same wind shear encounter. The wind shear may also be increasing in intensity, making flight through the wind shear more dangerous for following traffic.

Due to cockpit workload, reports may be initially reported as wind shear escape and
a full report provided when workload allows.

The full report must include:

• an assessment of the intensity:
  • light – shear causing minor excursions from flight path and/or airspeed
  • moderate – shear causing significant effect on control of the aircraft
  • strong – shear causing difficulty in keeping the aircraft to desired flight path and/or airspeed or
  • severe – shear causing hazardous effects to aircraft controllability
• a factual plain language report regarding airspeed/ground speed changes (gain or loss) or undershoot/overshoot effects
• the altitude or altitude band at which the adverse effect was experienced and
• where practicable, other relevant information such as significant changes in wind direction and/or speed may be included.

At non-controlled aerodromes, the report should also be broadcast to all aircraft on the CTAF and should include the name of the aerodrome.

The responsibility to continue an approach to land, or take off, following notification of low-level wind shear rests with the pilot in command.

Automatic meteorological broadcasts AIP GEN 3.5

Routine broadcasts of selected operational meteorological information for use by aircraft in flight are made from suitable locations using discrete ground-to-air frequencies.

Automatic en route information services (AERIS)

The AERIS continuously broadcasts METAR from a network of VHF transmitters installed around Australia. Details of transmitter sites, frequencies and locations for which METAR are provided are at ERSA GEN – FIS – INFLIGHT.

VHF automatic en route information service (aeris) network (coverage at 20,000 ft)

AIREP

AIREP Special AIP GEN 3.5

A pilot in command should make a special AIREP report when requested, or as soon as practicable after encountering any SIGMET phenomena (see page 2.36) which has not been notified, or any other MET condition which is likely to affect the safety or markedly affect the efficiency of other aircraft.

The estimate of next position may be omitted from an AIREP Special report except where the report is made at a planned position reporting point.

In the climb-out and approach phases, a pilot in command must report meteorological conditions, not previously advised, which are likely to affect the safety of aircraft operations.

Short AIREP

Short AIREP should be provided by pilots when requested. ATS should be advised when a pilot encounters:

• cloud – unexpected significant variations to amount, base or tops (by reference to QNH)
• visibility – reduced due to fog, mist, hail, rain, snow or dust, or improvement observed
• wind – significant variation to forecasts and/or/li>
• other phenomena – incidence of severe or moderate turbulence, thunderstorms, moderate or severe icing, hail, line squalls, standing waves or winds of 40 kt or more within 2000 ft of ground level.

The report comprises:

• callsign of the ground station
• callsign of the aircraft
• short AIREP
• either
  • position and time, or
  • ‘en route (departure point) to (destination)’ and
• a weather report.