Blog

Typically I ignore everything after RMK (Remarks) in a METAR, because I haven’t learned what they mean (did you know that METAR stands for MEteorological Terminal Aviation Routine Weather Report?  Me neither…).  But our AWOS shows some additional codes every three hours, and I got curious, so I’ll share what I’ve found.

Here’s our recent METAR: KFNL 031156Z AUTO 06006KT 10SM BKN100 15/08 A2980 RMK AO2 PK WND 28027/1107 SLP036 6//// 7//// T01500078 10222 20133 53006 PNO $

We can all probably decode the first part:

• KFNL: Northern Colorado Regional Airport
• 031156Z: October 3 at 11:56Z or 05:56MST
• AUTO: automated weather observation: no humans were involved in the generation of this report
• 06006KT: winds 60° at 6 knots
• 10SM: visibility 10 statute miles or better
• BKN100: ceiling broken at 10,000′ AGL
• 15/08: temperature 15°C (59°F) / dewpoint 8°C (46°F)
• A2980: altimeter 29.80″Hg
• RMK: remarks (or in my usual case, “stop reading here”)

Via the magic of the internet, I’ve looked up what each of the items in our remarks section mean.

• AO2: this is a weather station with a precipitation sensor.  However, skipping to the end…
• PNO: precipitation sensor is not working, and…
• $: the station has put in a call for maintenance.  Pretty cool!
• PK WND 28027/1107: Peak wind 280° at 27 knots occurred at 11:07Z (05:07MST)
• SLP036: The calculated sea level pressure in tenths of millibars (mb) is 1003.6mb (you have to know whether to preface the three digits with “10” or “9” depending on whether the they form a large number or a small number).  This is the field pressure, corrected for elevation and then for temperature, and is indicative of the field’s density altitude.  In this case it’s lower than the standard sea level pressure of 1013.25mb, so our density altitude is higher than our elevation.
• 6////: This element only makes its appearance in the METAR every three hours, at the 0Z, 3Z, 6Z, 9Z, 12Z, 15Z, 18Z, and 21Z observations (note that the observations occur just prior to the top of the hour, so the 12Z observation we’re decoding happened at 11:56Z).  The preface of a “6” indicates rainfall, in 0.01″, in the past six hours.  “60000” indicates a trace of precipitation, so “6////” is used to indicate no rain at all.  But with PNO being reported, the station actually has no idea whether it’s raining at the moment…
• 7////: This element only makes its appearance in the METAR once a day,  at the 12Z observation.  The preface of a “7” indicates rainfall in the past 24 hours.
• T01500078: if you’re interested in 0.1°C accuracy on the temperature/dewpoint, this one’s for you.  It’s two 4-digit fields.  The first digit is 0 for positive temperature and 1 for negative temperature.  In this report, it indicates temperature 15.0°C (59.0°F) and dewpoint 7.8°C (46.0°F).
• 10222: This element only makes its appearance every six hours, at the 0Z, 6Z, 12Z, and 18Z observations.  The preface of a “1” indicates highest temperature in the past six hours.  For this report, temperature peaked at 22.2°C (72.0°F).
• 20133: This element also appears every six hours.  The preface of a “2” indicates lowest temperature in the past six hours.  For this report, temperature was down to 13.3°C (55.9°F).
• 53006: This element only appears every three hours.  The preface of a “5” indicates the pressure tendency in the past three hours.  The first digit has to be decoded from this table:
  The other three digits are in tenths of mb.  In this report, the pressure is increasing at an accelerating rate (Code 3 in the table), and has risen 0.6mb (0.02″Hg) in the past six hours.

So, there you have it.  You can periodically tell from the remarks section what the weather trend has been at the airport: temperature range (every six hours), precipitation totals (every three hours), and pressure trend (every three hours).