Aviation weather is a very broad and diverse topic. Pilots can get their weather information from many different sources and in many different formats.
Even though it had been succeeded by newer formats, textual weather is still widely used by pilots today, and it is a requirement of all pilots to know how to read and interpret text based weather reports.
In this edition of Spotting 101, we will explain how to read a METAR (routine meteorological aviation weather report), and TAF (terminal aerodrome forecast)
Definitions:
METAR (Routine meteorological aviation weather report)
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A METAR is a weather report for a specific airport issued usually once every hour, at about 50 past the hour. Most METARs today are automated. This is very similar to the ATIS that is also updated hourly, and some airports have both METARS and an ATIS broadcast.
TAF (Terminal Aerodrome Forecast)
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A TAF is a forecast established for the 5 statute mile radius around an airport. TAF reports are usually given for larger airports. Each TAF is valid for a 24-hour time period, and is updated four times a day at 0000Z, 0600Z, 1200Z, and 1800Z. The TAF utilizes the same descriptors and abbreviations as used in the METAR report.
The difference between the two is this:
A METAR is a snaphot of what is happening right now, a TAF has a snapshot of when the TAF was recorded, plus a forecast of the next 24 hours, with predictions of weather conditions every 6 hours.
METAR
Lets look at a sample METAR report:
METAR KDWH 020453Z COR 18508KT 10SM +TSRA BR BKN007 OVC011 08/01 A3015 RMK AO2
Now, lets break the report down:
| METAR | KDWH | 020453Z | COR | 18508KT | 10SM | +TSRA BR | BKN007 OVC011 | 08/01 | A3015 | RMK AO2 |
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| 1 | METAR | Type of report (METAR or SPECI) |
| 2 | KDWH | Station identifier (David Wayne Hooks) |
| 3 | 020453Z | Date / Time 02 = 2nd day of the month 0453Z = Time in Zulu |
| 4 | COR | Modifier COR = corrected report |
| 5 | 18508KT | Wind direction and speed. 185° at 8 knots |
| 6 | 10SM | Visibility reported in Statute Miles (10 is the most that will ever be reported) |
| 7 | +TSRA BR | Heavy thunderstorms and rain showers, mist |
| 8 | BKN700 OVC011 | Broken cloud layer at 700 ft., Overcast cloud layer at 1,100 ft |
| 9 | 08/01 | Temperature (C°) / Dew point (C°) |
| 10 | A3015 | Barometric pressure (in inches of mercury) 30.15hg |
| 11 | RMK A02 | Remarks = AO2 (type of detection system) |
TAF
Lets look at a sample TAF report:
KIAH 020525Z 020606 04004KT P6SM SKC
FM1200 07005KT P6SM SCT020
FM1500 10007KT P6SM BKN020
Now, lets break the report down:
| KIAH | 020525Z | 020606 | 04004KT | P6SM | SCT040 | FM1200 07005KT P6SM SCT020 | FM1500 10007KT P6SM BKN020 |
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| 1 | KIAH | Station identifier |
| 2 | 020525Z | Date / Time of forecast (02=Day, 0525Z=Time (Z)) |
| 3 | 020606 | Valid time (02=Day, 06=From time (0600Z), 06=To time (0600Z, the following day) |
| 4 | 04004KT | Wind direction and speed (040° at 4 knots) |
| 5 | P6SM | Greater (plus) than 6 Statue Miles visibility |
| 6 | SCT040 | Scattered cloud layer at 4000 |
| 7 | FM1200 07005KT P6SM SCT020 | From 1200Z, wind will be 070° at 5 knots, +6 SM visibility,scattered clouds at 2000 ft. |
| 8 | FM1500 10007KT P6SM BKN020 | From 1500Z, wind will be 100° at 7 knots, +6 SM visibility,broken clouds at 2000 ft. |