AIP GEN 3.5 Section 3 gives general information regarding aviation weather reports and forecasts.
AIP GEN 3.5 Section 12 gives information on how how decode aerodrome weather and forecasts including TAF, TTF, METAR and SPECI.
Some important points to note include :
- the validity periods of each type of forecast;
- wind direction is rounded to the nearest 10 degrees and given in three figures relating to TRUE north;
- a TTF supercedes a TAF for its 3 hour validity period;
- CAVOK means:
- visibility greater than 10 km; and
- no cloud below 5,000 feet and no cumulonimbus or towering cumulus at any height; and
- no significant weather.
- Cloud Reports
- FEW = few = 1 to 2 OKTAS;
- SCT = scattered = 3 to 4 OKTAS;
- BKN = broken = 5 to 7 OKTAS;
- OVC = overcast = 8 OKTAS.
You should be familiar enough with the format of these weather messages to be able to read them in plain english eg.
SPECI YMML 092000Z 22012KT 6000 SHRA SCT035TCU 31/20 Q1020 RETS RMK RF02.0/004.0 translates to:-
Special observation report made 10 minutes after an improvement in conditions. This report was made at Melbourne (YMML) airport on the 9th at 2000Z. Wind is from 220o TRUE at 12 Knots. Visibility is 6000 metres. There are showers and rain in the area. There is between 3 and 4 eighths of the sky covered in cloud with a base of 3,500 feet. The cloud is of towering cumulus type. The temperature is 31oC and the dew point is 20oC. The aerodrome QNH is 1020 hPa. There have recently been thunderstorms in the area. There has been 2.0 mm of rain in the past 10 minutes and 4.0 mm since 0900 local time.
Here are some additional resources to help you learn how to decode aerodrome weather reports and some example severe weather aerodrome weather reports. We have an aviation weather decode card available for download which you can use as a quick reference guide .
There is also some excellent educational materials on the Bureau of Meteorology Aviation E-Help page. To get access to the registered users services use username: bomw0007 password: aviation.
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Decoding Aviation Weather Reports - TAF, TTF, METAR, SPECI - - Technical data content credited to Mr Steve Griffin