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Textual aviation weather


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)

  • A METAR is a weather report for a specific airport issued usually once every hour, at about 50 past the hour.  Most METAR's 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)

  • 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)
Click here for more detailed information about the METAR report


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.

Click here for more detailed information about the TAF report