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Forecasts and Reports

Aviation Products

METAR

A METAR is a snapshot report indicating the current meteorological conditions at the time the report is issued. In the context of flight simulation, it can be used to aid situational awareness and conduct performance calculations, but not for any flight planning purposes. METARs are published on a fixed time schedule, generally every thirty minutes.

SPECI

A SPECI is a METAR which has been published outside of the regular cycle due to abnormal weather conditions or large meteorological changes since the last report. It serves the same purpose as a METAR and cannot be used for flight planning purposes.

SPECIs may be published for a range of conditions, including:

  • A sudden shift in wind, temperature, or QNH
  • Visibility below the alternate minima or 5km
  • BKN or OVC cloud below the alternate minima or 1,500ft
  • Significant weather such as thunderstorms or fog

TAF

A TAF is an aviation forecast which covers a small radius of the nominated location. It can be used to determine the forecast weather conditions at an aerodrome for the purposes of flight planning.

TAFs at some major aerodromes include the TAF3 remark, indicating that they are updated more frequently and to a more accurate standard during the first three hours of their validity. Some flight planning concessions apply to TAF3s, which are detailed in AIP ENR 1.1 10.

Area Forecasts

A number of visual area forecasts are available, which provide forecast weather conditions in a wider area. These can be used to determine the enroute weather conditions (and any associated limitations) and to provide an appreciation for the weather at aerodromes without a dedicated weather report/forecast.

Area forecasts are generally available on the NAIPS website and include GAF (for use at or below A100) and SIGWX (for use between A100 and F630) products.

Where to Find Them

METARs and TAFs can be sourced from a number of sources.

  • NAIPS: Real world system maintained by Airservices Australia, providing access to reports, forecasts, first/last light calculations, a large variety of meteorological charts, and more
  • VATPAC Pilot Tool: An all-in-one tool providing access to weather reports, forecasts, and ATISes, as well as easy access to aerodrome charts for your nominated origin and destination
  • VATPAC Weather Data Tool: A dedicated tool allowing members to access weather reports, forecasts, and ATISes, without linking a specific VATSIM flight

Interpreting Data

Written Reports/Forecasts

METARs/SPECIs and TAFs reference the following datums:

Element Datum
Wind Degrees true
Cloud Feet AAL

METAR

METARs/SPECIs follow a specific format which makes interpreting them straightforward.

Format

    flowchart LR        
    A[*METAR/SPECI*] --- B[Location] --- C[Timestamp] --- D[*AUTO*];
    flowchart LR
    E[Wind] --- F[Visibility] --- G[Weather] --- H[Cloud];
    E --- Z[*CAVOK*] --- I[Temperature/Dew Point];
    H --- I;
    flowchart LR
    J[QNH] --- K[Other Remarks];

Visibility, weather, and cloud will be omitted when the requirements of CAVOK are met. Any element which is not available (due sensor failure or otherwise) will be replaced by forward slashes.

Example

METAR YSSY 220000Z 13011KT 9999 SHOWERS IN VICINITY SCT035 SCT045 BKN055 19/17 Q1019 RMK RF00.0/000.4

Recent rainfall is commonly included in the remarks section, displaying the amount of rain in the previous 10 minutes and the amount of rain since 9am local time (separated by a forward slash). In the METAR example above, YSSY has had 0mm of rain the past 10 min and 0.4mm of rain since 9am local.

TAF

TAFs are comprised of a header and footer section, with the actual forecast weather contained between.

Example

TAF YSSY 212309Z 2200/2306
09014KT 9999  LIGHT RAIN SCT008 BKN020
FM220800 08016KT 9999 SHOWERS OF LIGHT RAIN SCT008 BKN013
FM222000 04016KT 9999 SHOWERS OF LIGHT RAIN SCT008 BKN013
BECMG 2300/2302 04016KT 9999 SHOWERS OF LIGHT RAIN SCT010 BKN016
TEMPO 2200/2208 07015G25KT 2000 SHOWERS OF MODERATE RAIN BKN008 SCT020TCU
TEMPO 2208/2306 05020G30KT 2000 SHOWERS OF MODERATE RAIN BKN008 SCT020TCU
RMK
T 19 18 18 18 Q 1019 1017 1016 1017
TAF3

Format

    flowchart LR
    A[*TAF*] --- B[Location] --- C[Timestamp] --- D[Valid From/Valid To]

The validity period expresses time as a four digit timestamp in the format of DDHH. In the example below, the forecast is valid from 2200 (0000z on the 22nd day of the month) until 2306 (0600z on the 23rd day of the month).

Example

TAF YSSY 212309Z 2200/2306

Weather

Each line of the TAF represents a period of time and the associated forecast weather for that period.

Format

    flowchart LR
    A[Change Indicator] --- B[Wind] --- C[Weather] --- D[Cloud]

The first line of the TAF has no change indicator and is valid from the commencement of the validity period.

Example

09014KT 9999  LIGHT RAIN SCT008 BKN020
FM220800 08016KT 9999 SHOWERS OF LIGHT RAIN SCT008 BKN013

Several change indicators are used to indicate that the associated weather is only relevant during a given time period.

Abbreviation Meaning
FM The weather is expected to change from the given timestamp onwards, until the next change indicator
BECMG The weather is expected to change slowly between the two four digit (DDHH) timestamps, until the next change indicator
INTER The forecast weather is expected to be present for periods of up to 30 min between the two four digit (DDHH) timestamps
TEMPO The forecast weather is expected to be present for periods of up to 60 min between the two four digit (DDHH) timestamps

Where there is a probability of thunderstorms or poor visibility, an INTER/TEMPO will be prefixed with either PROB30 or PROB40.

Example

A TAF detailing PROB30 TEMPO 2202/2204 VRB20G30KT 2000 SHOWERS OF MODERATE RAIN BKN003 SCT025TCU would describe a 30% probability of up to 60 min of gusty, variable wind, showers of rain, and low cloud between 0200z and 0400z on the 22nd day of the month.

Remarks

The end of the TAF forecasts the outside air temperature and QNH at three hour intervals. Additional remarks may be included, such as indicating the forecast's TAF3 status.

Example

RMK
T 19 18 18 18 Q 1019 1017 1016 1017
TAF3

Common Abbreviations

The VFRG (and AIP GEN 3.5) lists common abbreviations used in aviation meteorological products. A small selection are shown below:

Abbreviation Weather Descriptor
BC Patches
BL Blowing
DR Drifting
FZ Freezing
MI Shallow
SH Showers
TS Thunderstorms
PR Partial
VC Vicinity
Abbreviation Weather Phenomena
BR Mist
DU Dust
FG Fog
FU Smoke
HZ Haze
RA Rain
VA Volcanic Ash

Example

A METAR detailing SHRA would describe showers of rain.

A METAR detailing VCTS would describe thunderstorms in the vicinity.

A METAR detailing BLDU would describe blowing dust.

Intensity Qualifiers

Precipitation, dust storms, and sandstorms may be prefixed with an intensity qualifier to denote how intense the weather phenomenum is.

Prefix Meaning
- Light
Moderate
+ Heavy

Example

A METAR detailing +SHRA would describe heavy showers of rain.

Weather Information Services

Weather services like AWIS and ATIS reference the following datums:

Element Datum
Wind Degrees magnetic
Cloud Feet AAL