METAR reading

cointyro

New Member
I've a question on METAR reading. Often at the very end of a METAR is a figure that looks like 58033. I know the 5 indicates pressure change figures; the "8" characterizes that change; and "033" is the amount of that change.

My question is this: how often do pilots (GA and professional) actually use this 5appp / pressure change METAR figure? Should I memorize the "character" number meanings, or is this something that is better verbally covered in a flight wx briefing?
 

EatSleepFly

Well-Known Member
Not very often I don't think. I've never been asked it. In fact, I just learned something new. I had no idea what those numbers at the end meant.
 

cointyro

New Member
Another question (moderately unrelated) is this: A southerly wind is out of the south, right? A north wind is out of the south too, right? The "-erly" appellation makes all the difference I guess...
 

Visceral

Well-Known Member
I always understood it to be the southernly or northernly meant "in general out of the south/north." A wind direction of 160 isn't due south per se, but its southernly. I haven't seen anything that says the "ly" means anything different.
 

cointyro

New Member
Thanks guys. So I now know "a wind out of the south" is the same thing as a "southerly wind" which would be, say, 18020KT on a METAR.

But if someone says "we have a north wind tonight", what do they mean? Or "such-and-such this time of the year is a east wind...".
 

pljenkins

Resident Knucklehead
Well.. Best way to explain it is an example...

KORD 182256Z 06012G19KT 10SM FEW250 22/10 A3009 RMK AO2 SLP187 T02170100

Are you asking about "T02170100"? That is the temperature and dewpoint expressed to the tenths. Broken down, "T" is, well, Temperature... The first bank of numbers is the temperature are "0217". The first number, 0, means that the temperature is positive, and the next three tell us that the actual temperature is 21.7 degrees. If the temperature were negative, the leading zero would be a "1". The last four digits work the same way, expressing that the dewpoint is positive 10.0 degrees.

But to the real meat of your question.. I, nor any pilot I work with, use it. The main temperature/dewpoint factors are rounded anyway, and all the charts use whole numbers. You could logically extrapolate these numbers I suppose, but would a pilot really know when he's hit his V1 speed of 142.23 knots? <grin>

"Engine Failure"

"Speed is 142.11, abort takeoff!"

<grin>

Oh.. wind direction.. this one screwed me up for a while. Best way I figured out how to make it work.. Always preceed your reading of the wind with "out of". So, the wind in Chicago is "out of" 060 at 12 knots, gusts to 19. Point to 060 and the wind is in your face.

Paul
 

cointyro

New Member
Thanks Paul for the responses.

Actually, though, I wasn't referring to the Txxxxxx... figure which as you said is OAT and dewpoint with tenths of degree.

To explain further, here is a METAR example:

KSMO 190551Z AUTO 24003KT 5SM BR CLR 21/21 A2999 RMK AO2 SLP155 T02110211 10233 20211 50001

I was referring to the last figure on this METAR, the 50001, which according to official NOAA / FAA codes, refers to the recent change in pressure. The first number (5) clues you in to what the data block means; the second digit tells the characterization of the change (increasing then decreasing, OR decreasing then decreasing faster, OR etc), and the last three digits tell the amount of pressure change.

But based on previous responses it seems that this 5xxxx figure doesn't matter that much.

As for the wind, yes I agree... by preceding with the phrase "out of" there is little confusion. A southerly wind is out of the south, and a 18020KT METAR code means a wind out of the south.

But have you ever heard, in other contexts, of someone describe a north wind? I.e. do meteorologists or weather textbooks or anyone else call a "north wind" as a wind blowing north... while a "northerLY" wind is a wind blowing OUT OF the north? Just checking to make sure that if I say "there is a north wind" or if I hear a weatherman say "there is a north wind tonight" (and he DID NOT say "northerly") then I know what he is saying... although ultimately of course I agree and will comply completely with your recommendation that the -ly convention and the use of "out of 090" etc. convention are much more clear as a verbal indicator.

Thanks all!
 

Bluto

New Member
In aviation, winds are always described in the direction from which they come. The reason for this is that we, as pilots, are the center of the universe. What the wind does after it passes us (ie. where it is blowing to) is of no concern. Therefore, the only direction that matters is where it came from, since wherever it is going, we are not there. Clear?
 

cointyro

New Member
Nice METAR, marginal wind, Ceiling and Visibility OK, no chance of fog or clouds since OAT is so far from the dewpoint / relative humidity is so low, pressure is high which reinforces the clear weather...

right?
 

pljenkins

Resident Knucklehead
Seems that way... Of course, it doesn't hurt that TJSJ is San Juan, Puerto Rico! <grin>

Of course, as a dispatcher, this is PURE music to my ears...

KEYW 192320Z 200024 11007KT P6SM SCT020=



Paul
 

pljenkins

Resident Knucklehead
Actually, that's a TAF...

The 200024 means that the TAF is valid from the 20th of the month (20) from 0000z (00) to 2400z (24), or a 24 hour period.

Unless you're operating flight legs that run under 30 minutes, you almost never dispatch off the METAR, since by the time you get there, it will be superceded by the next METAR.

Not saying you can't do it. If you have a flight that leaves at say 0015z and is due to arrive at 0050z you can dispatch off the METAR, since it would still be valid from the time he departed to the time he arrived. This is a creative way to get around a TAF that would otherwise have grounded you.

Paul
 

Bluto

New Member
I'm surprised you can dispatch a flight based on a Metar at all since they don't really have a 'valid time'. A metar is an observation. I was under the impression that to dispatch a flight you'd have to have a forecast for the eta. Is that not accurate?
 

BLRJSTREAM

New Member
At my company we can dispatch a flight off of a series of METARS (at least 3) showing an upward trend, But the forcast must be legal. Meaning if you are using 3585 then the METAR should be considered but not dispatched off.
Also there is a valid time for a METAR its until the next one is issued (usually 15mins).
 

Terpy

Member
Well.. Best way to explain it is an example...

KORD 182256Z 06012G19KT 10SM FEW250 22/10 A3009 RMK AO2 SLP187 T02170100

Are you asking about "T02170100"? That is the temperature and dewpoint expressed to the tenths. Broken down, "T" is, well, Temperature... The first bank of numbers is the temperature are "0217". The first number, 0, means that the temperature is positive, and the next three tell us that the actual temperature is 21.7 degrees. If the temperature were negative, the leading zero would be a "1". The last four digits work the same way, expressing that the dewpoint is positive 10.0 degrees.

But to the real meat of your question.. I, nor any pilot I work with, use it. The main temperature/dewpoint factors are rounded anyway, and all the charts use whole numbers. You could logically extrapolate these numbers I suppose, but would a pilot really know when he's hit his V1 speed of 142.23 knots? <grin>

"Engine Failure"

"Speed is 142.11, abort takeoff!"

<grin>

Oh.. wind direction.. this one screwed me up for a while. Best way I figured out how to make it work.. Always preceed your reading of the wind with "out of". So, the wind in Chicago is "out of" 060 at 12 knots, gusts to 19. Point to 060 and the wind is in your face.

Paul
I use this all the time as a dispatcher in Alaska. Especially when the temps are near 0 and there is precip. I can tell if it's getting colder and rain is going to turn to snow later mostly for runway's that are unmonitored.
 
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