METAR RMKs

charley varrick

Last of the independents
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Nov 26, 2001
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Boning up on my METARS, and I can't for the life of me find out where it states what the second digit in these pressure trends means. Anything I read only says that it states the "character" of the trend.

KBOS 261154Z 28006KT 10SM FEW160 SCT250 21/14 A3001 RMK AO2 SLP160 T02060144 10211 20183 51018

KMSP 261153Z 00000KT 10SM FEW055 BKN250 19/17 A3006 RMK AO2 SLP175 ACC DSNT SW-NW T01940172 10211 20183 53003

KSFO 261156Z 26004KT 10SM FEW008 13/11 A3006 RMK AO2 SLP180 T01280111 10139 20128 58007

I'm referring to the last bit on each of the above, the 5(number)nnn . . . anybody got the rosetta stone for this one?

Thanks!
 

SpinDoctor

Live free or die
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Jan 30, 2002
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He says to me, "Gunga-ga-lunga"

Charley, and for those of you who actually give the south end of a north bound rat-

The answers are in Advisory Circular, AC 00-45D, titled "Aviation Weather Services", in chapter 2. I'll take for granted that the regular info in the METAR can be decoded, but as for the remarks section-

If the 5 digit section begins with a 1 it means the MAXIMUM TEMPERATURE recorded during the last 6 hours. So for Boston 10211 means that the max temp was 21.1. Also if the maximum temperature happens to be negative then the second digit will not be 0, it will be 1.

If it begins with a 2, it is the MINIMUM TEMPERATURE recorded within the last 6 hours. So for Boston showing 20183, the min temp was 18.3. Same as above with the minimum temperature being negative.

If it begins with a 5 is is the PRESSURE TENDENCY IN MILLIBARS during the last 3 hours. The 5 is for the pressure and the next number indicates whether it is rising or falling. If the second digit is a 0, 1, 2, or 3 then the pressure has risen by 01.8 millibars in the past 3 hours for Boston in the METAR that you gave.

If the second digit is a 5, 6, 7, or 8, then the pressure is lower than 3 hours ago. So for San Fran the pressure has fallen by 0.7 millibars in the past 3 hours.

If the second digit is a 4, then no change has occured in the past 3 hours. 9 is not used as a second digit due to the possible confusion with the reading being in the 900s of millibars range.

And finally if the first digit of the 5 digits is a 7, then it stands for the 24-HOUR PRECIPITATION. So 70125 inciates 1.25 inches of precip in the last 24 hours.

Thanks for the review and now I feel like a nerd for having known the answer and where to find it. But at least I'm a good looking nerd (or so my mom tells me).
 
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