Aviation weather reports are pretty simple once you’ve been trained to read and interpret them, but the more often you fly, the more often you’ll see new and strange codes on METARs (aviation routine weather reports). Some of these are decoded below. A few of these are codes that you may have learned for your check ride but forgot about years later, and others are just plain rare or insignificant.
For more details on METAR codes and other aviation weather reports, check out the FAA advisory circular AC-0045-G, Aviation Weather Services. This particular advisory circular is very thorough, and even if you were previously educated on the codes below, you’re likely to learn a thing or two about Aviation Weather Services from this one.
Here are a few METAR codes that are commonly forgotten, misinterpreted, or never learned. How many do you know?
BKN014 V OVC
Most of us know that this means there’s a broken cloud layer at 1400 feet AGL. But what’s the ‘V’ mean? The ‘V’ here means that the cloud layer at 1400 feet is variable between broken and overcast. It’s a code that’s not that commonly seen.
CIG 002 RWY11
If you see the code above and there’s already a ceiling reported earlier in the METAR report, it means that there’s a second station on the field that’s also reporting visibility, and you’ll know this because the specific location will be included. This ceiling is only included if the ceiling at this second station is lower that otherwise reported in the METAR. Here, it means the ceiling is 200 feet at the ceilometer location near runway 11.
If the snowfall increases by one inch or more since the previous reported METAR, it’s indicated by ‘SNINCR’ followed by the amount. In the case above, the snow has increased by 2 inches in the past hour, and the total snowfall is 10 inches. This could be easily misinterpreted as a snow increase of 2/10 of an inch, so it's worth remembering.
A01 and A02
A01 and A02 are types of METAR stations. This code, which is often brushed aside as meaningless by some, distinguishes between a station with a precipitation discriminator (A02) and one without (A01).
The dollar sign at the end of a METAR indicates that the station has self-identified itself as needing maintenance. This one is pretty common, but not all pilots take the time to figure out what it means.
This notation gives the time that special weather events began (noted by the ‘B’) and if they’ve ended, what time they ended (noted by an ‘E’). The text above means that thunderstorm began at 22 minutes past the hour, rain began at 17 minutes past the hour, and hail (GR) began at 23 minutes past the hour.
If the pressure rises or falls at a rate of 0.06 inches per hour, and the difference from the last reported pressure is 0.02 or greater, than the code PRESRR will be used, which stands for pressure rising rapidly, and the code PRESFR will be used to note pressure falling rapidly.
PNO or CHINO LOC
At the end of a METAR, you may often find an abbreviation ending with ‘NO’. These are most likely sensor status indicators. There are a few different possibilities for these sensor abbreviations. Above, PNO means that the "tipping bucket rain gauge" sensor isn’t working. ‘CHINO LOC’ means that the sensor for the secondary ceiling height indicator is not operating. As you can see, some of these aren’t necessarily intuitive, and will often require you to dig deeper to determine what they mean.
These are just a few of the commonly unknown METAR codes. There are many more, as you’ll discover by reading the advisory circular suggested above.
Which strange codes have you stumbled upon while checking the weather?