Reading a Metar, part 1

Taz Christman is the 2018 Flight Instructor of The Year. Click that title and check him out! He presents some of the video you will see in the Remote Pilot Online Course.

Reading a Metar, part 1

We’re going to continue talking about weather, and we’re going to start with weather services.

In this lesson, we’re going to talk about Aviation Routine Weather Reports or METARs. Aviation Routine Weather Reports, or METARs, are an international weather reporting code that is used for weather reports and forecasts worldwide.

And here’s a couple of pictures of some decoding sheets. You can usually find these anywhere. Actually, it’s in your AIM and, pretty much, you can just do a Google search and you can find them.

A METAR is an observation of current surface weather reported in a standard international format compiled from current weather gathered from ground stations across the United States. While the METAR code has been adopted worldwide, each country is allowed to make modifications to the code.

Normally, these differences are minor but necessary to accommodate local procedures or particular units of measure. The information gathered for the surface observations may be from a person, or a weather observer in an automated station or a combined automated weather station as it is updated or enhanced by a weather observer.

So an automated station is great, but if there’s nobody there actually looking at it to make sure it’s giving you the right information, you don’t know, you’re just assuming that it’s accurate.

Most of them are pretty accurate. I’ve got a good one from one of my professors when I was back in college. He was talking about when they first started these automated stations. They put them him up in Alaska. They do a lot of weather testing and all kinds of stuff in Alaska at first.

Reading a Metar, part 1

One of the things they did is they put these automated weather stations out there, and they started getting these random reports from this one station where the pilots would fly in and it’d be completely clear, sun shining, not a cloud in the sky.

But this station was reporting that the sky was obscured, or the visibility was at a quarter of a mile, or just something crazy that it was clearly not what was going on. And what they found out was the moisture would adhere to the station because they’re made out of metal. So it would adhere to it.

The elk and caribou and whatever other animals up there, they’d go up to it and start licking it. And what that would do is that just built up more saliva or snot, or whatever the animals would do to it, and it would clog up the sensors and it wouldn’t be reading right.

What they ended up having to do was put a bunch of fences around these things and try to keep the animals from getting to it. In that case, that’s a good reason why you have a person to enhance it.

So all your big terminal areas, your big airports here with control towers and stuff like that, they’re probably going to have an automated station just because it’s pretty easy. And, then, they’re just going to be augmented by usually one of the tower controllers.

Or in some of the bigger ones like McCarran here, we actually have a national weather service personnel who actually updates the METARs to make sure they’re all correct. For aviation purposes, the ceiling is the lowest broken or overcast layer, or vertical visibility into an obstruction.

As you can see in this picture here, what they do is they actually divide the environment up into eighths. So the entire sky is divided up in eighths. You’ve got one, two, three, four, five, six, seven, eight there. What they do is, anytime there’s a cloud in one of these eighths here, that defines what kind of clouds it is.

So, if you look over here at Sky Cover, if it’s less than an eighth, it’s clear. So down here, less than a thousand feet, there’s no clouds in there so the sky is clear below a thousand feet. Now, you go up here to a thousand feet, and you’ve got one cloud over in this sector, and you’ve got one cloud over here, so there’s two eighths, or it’s few.

So you have few clouds at one thousand feet. There here again, there’s no clouds at two thousand. You go up to three thousand feet, and you’ve got one, two, so there again you’ve got few clouds at three thousand feet.

Go on up to five thousand feet here, you’ve got one, two, three, four, so you’ve got four eighths. So, if you’ve got four eighths, here’s going to be scattered. So three to four eighths is going to be scattered. Anything over four eighths, so five eighths or greater is going to actually be your ceiling.

Reading a Metar, part 1

So that’s the lowest of a broken or overcast layer. Anything over that four eighths is a broken. So, if they’d add another cloud in any of these other sectors, then you would have that five eighths, which would be a broken.

Overcast would be if it’s completely covered, so there’s clouds in all eighths of that section in there. There are two types of METAR reports. They have the routine METAR report that’s transmitted every hour, usually within ten minutes before the top of the hour.

And, then, you have the SPECI, which is a special report that can be given at any time to update the METAR for rapidly changing weather conditions, aircraft mishaps, or any other critical information.

Here’s another eye chart showing the elements of a METAR. You have the four-letter ICAO identifier. You have the date and time of report appended with a “Z” to denote Zulu or UTC time. If there’s any kind of modifier for the report, that’s going to be in there.

Winds are going to be reported as a five-digit group appended with a KT to denote the use of knots. If the winds are gusty it is reported with a “G” followed by the highest reported gust. Visibility is going to be reported in statute miles, runway, visual range.

If that’s reported that’ll be in there -- any kind of weather phenomena, sky conditions. So there again, like we said, the ceiling is considered the lowest broken or overcast layer or vertical visibility into an obscuration.

Temperature/dewpoint in two-digit form in a whole degree Celsius. You have your altimeter and then any kind of remarks. Let’s read through this one with us. So we have a METAR. It’s a routine observation.

It’s for Austin, Texas. So on the 30th day at 16:51 Zulu, the winds are One-Two-Zero at eight knots. Sky are at four statute miles visibility. Light rain and haze. Broken at one thousand feet. Overcast at two thousand three hundred feet. Temperature’s Two-One. Dew point is One-Seven.

Altimeter is Three-Zero-Zero-Five. And you’ve got your remarks. The rain began 25 minutes after the hour. Here’s another good chart. We’ll just kind of hit on a few of these. There’s nothing too pressing about these. Most of these you can kind of understand, and most of this should be a review for you guys anyway.

You should have your private or commercial by this point, and you should already know most of these, but we’ll hit on a few of them. This chart can be found in your Pilot’s Handbook of Aeronautical Knowledge, which is a great book.

It’s also in your Aviation Weather Services book. Here’s your qualifier over on this section right here. This always goes with the precipitation over here. A lot of times, what you’re going to see, for instance, you might have the minus sign here with thunderstorms and then rain.

What they’re actually looking at there is it’s actually light rain and thunderstorms, not necessarily light thunderstorms and rain. That’s one of those things that will get you. They try to do that on your written test, and don’t fall victim to that if you’re still working on the written test or if the examiner asks you during your practical.

There is no such thing as a light thunderstorm. Thunderstorms are bad, regardless. Any of these precipitation discriminators goes with this over here. Some of the easy ones, obviously, drizzle’s pretty easy to recognize (DZ). Rain’s RA. Snow, it makes sense. Some of the weird ones, though, is you’ve got this thing called hail down here and it’s GR.

One way I remember this is it’s granite rain. So, it’s rain that feels granite. Big rocks that are pounding at you, that would be the hail. So GR is hail. Some of the other ones I kind of like is BR for mist.

Mist is really fine rain, so I think of it as baby rain. So BR is baby rain. We’ve got a few more here, and we’re going to go through these, and I’m going to show you a few places where you can actually get some METARs.

Reading a Metar, part 1

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