How to decode standard upper-air observations:
TTAA YYGGI IIiii message identification 99PoPo ToToTaoDoDo dododofofo surface data 00hhh TTTaDD dddff 1000 mb data 92hhh TTTaDD dddff 925 mb data 85hhh TTTaDD dddff 850 mb data 70hhh TTTaDD dddff 700 mb data 50hhh TTTaDD dddff 500 mb data 40hhh TTTaDD dddff 400 mb data 30hhh TTTaDD dddff 300 mb data 25hhh TTTaDD dddff 250 mb data 20hhh TTTaDD dddff 200 mb data 15hhh TTTaDD dddff 150 mb data 10hhh TTTaDD dddff 100 mb data 88PtPtPt TtTtTatDtDt dtdtdtftft tropopause data 77 PmPmPm dmdmdmfmfm vbvbvava maximum wind data 66 51515 101AdfAdf Regional additional data
TTBB YYGG/ IIiii message identification 00PoPoPo ToToTaoDoDo surface data 11PPP TTTaDD 22PPP TTTaDD significant levels with .......... respect to temperature 99PPP TTTaDD and/or humidity changes 11PPP TTTaDD .......... PPBB YYGGa IIiii message identification 9tnu1u2u3 dddff dddff dddff ....... winds at fixed regional 9rnu1u2u3 dddff dddff dddff and significant levels
Note: lowercase "o" indicates surface data. lowercase "t" indicates tropopause data. lowercase "m" indicates data from the level of maximum wind TTAA/TTBB Type of report which procedes. AA is only mandatory levels, while BB is significant levels with respect to temperature and/or humidity. YY Day of the month (GMT) of the observation plus 50. Example: 55 = 5th day of the month. GG Time of observation to the nearest hour (GMT). Id Indicator of the last standard isobaric surface for which the wind group is included. The number '1' is used for 100 mb and above. IIiii Block and station number. PPP Pressure in millibars. TT Observed temperature of the air in whole degrees (not rounded to nearest degree) in degrees Celsius. Ta Approximate tenths value and sign of the air temperature. If Ta is even (0,2,4,6,8), the temp TT is positive; the temp is negative if Ta is odd (1,3,5,7,9). DD Depression of the dew point temp. When the depression is 5.0 degrees C or less, the units and tenths digits of the depression are reported. When the depression is more than 5.0 degrees C, the tens and units digits of the depression are reported, plus 50, wiht 51-55 not used. Thus, DD = 10 is a depression of 1.0 degrees c and DD = 60 is a depression of 10.0 degrees c. ddd Wind direction reported to the nearest five degrees. (Examples: 320 = 320 degrees, 060 = 60 degrees). NOTE: IF THE WIND DIRECTION APPEARS TO BE GIVEN TO THE NEAREST DEGREE, (e.g., 321) THE DIRECTION WOULD BE DECODED TO THE NEAREST FIVE DEGREES (320 degrees in this case) BUT THE SPEED WOULD BE INCRESASE BY THE UNITS DIGIT MULTIPLIED BY 100 KTS. SEE "ff" IMMEDIATELY BELOW. ff Wind speed in knots, or knots plus 100. hhh Geopotential altitude of the standard isobaric suface in meters to 700 mb and in dekameters at 500 mb and above. To convert the height value to meters: 850 mb: a leading 1 is necessary 700 mb: a leading 2 or 3 is necessary 500-300 mb: a following 0 is necessary 250-100 mb: a leading 1 and a trailing 0 is necessary 88 Tropopause data. (The tropopause is defined as the lowest level where the lapse rate dereases to 2 degrees C/km or less for at least 2 km.) 77 Maximum wind data (for winds exceeding 60 kts above 500 mb). 66 When the maximum wind occurs within the sounding, 77 is used; when the max wind occurs at the termination of the sounding, 66 is used. 4 Vertical wind shear indicator. vbvb Vector difference below maximum wind. The absolute value of the vector difference between the max wind and the wind blowing at 3000 ft below the level of the max wind, to the nearest whole knot. vava Same as 'vbvb' group except for 3000' above the level of the maximum wind. 51515 Regionally developed codes follow. 101AdfAdf 101 is regional additional data indicator, while AdfAdf is the additional data two number code. 9 Indicator for wind height groups. 11-99 Indicators for significant levels with respect to temp/humidity. In general, a significant level is defined as a level at which temp and/or RH data are sufficiently important, or unusual. When the plotted report is compared with the actual sounding trace, the relative humidity is within 10 percent and the temp is within 2 degrees C of the actual sounding.
71853 TTAA 52121 71853 99975 09421 03003 00163 ///// /////
85525 11056 25014 70122 01018 31018 50575 14320 31037 40741
24520 32544 30945 393// 33048 25067 499// 33057 20209 607//
33062 15384 665// 32547 10635 599// 33031 88180 661// 33563
77176 33563 41008 51515 10164 00012 10194 01013 34518=
EACH GROUPING DECODED, FOLLOWS:
71853 the block/station number 85525 850 mb info.
TTAA mandatory levels follow 850 mb ht. (1525m)
52121 52-50=02 2nd day of month 11056 11.0(degrees c) temp.
12 12Z 56-50=6(degrees c) dp. dep.
1 last reported
wind lvl=100 mb
99975 99 surface information 25014 250 degrees wnd. dir.
975 station pressure 14 kt wnd. spd.
09421 9.4(degrees c) sfc temp.
21 2.1(degrees c) dp. dep. 70122 700 mb info.
03003 030 wind direction 700 mb ht. (3122m)
003 wind speed (kts) 01018 1.0(degrees c) temp.
00163 00 1000 mb information 18 = 1.8(degrees c) dp. dep
163 1000 mb height (m) 31018 310 degrees wnd. dir.
///// missing data 18 kt. wnd. spd.
71853 TTBB 5212/ 71853 00975 09421 11921 14457 22847 10850
33782 08663 44697 00613 55636 03100 66631 04700 77468 17321
88423 23323 99400 24520 11344 31157 22305 38359 33180 661//
44162 669// 55147 665// 66143 625//=
DECODED:
71853 BLK/STN NUMBER 11921 11 first sig. lvl.
TTBB SIGNIFICANT LEVELS 921 mb
5212/ 52-50=02 2nd day 14457 14.4(degrees c) temp.
12 12Z 57-50= 7(degrees c) dp. dep.
/ last level NA 22847 22 second sig. lvl.
71853 blk/stn number 847 mb
00975 00 sfc data 10850 10.8(degrees c) temp.
975 mb stn. pres. 5.0(degrees c) dp. dep.
09421 9.4(degrees c) temp. 33782 33 third sig. lvl.
2.1(degrees c) dp. dep. 782 mb
08663 8.6(degrees c) temp.
63-50=13(degrees c) dp. dep.
PPBB 52120 72764 90023 12507 14511 18518 90467 20015 22507
24509 9089/ 25512 26512 91124 29012 29513 30021 916// 30024
92015 31030 32029 32032 93057 30535 33033 33032 94234 34549
35039 31530 946// 30542 9503/ 32536 32024=
DECODED:
PPBB winds at fixed levels
52120 52-50=02 02nd day
12 12Z
0 measured with pressure and wind instruments
72764 blk/stn number
90023 9 indicator for wind height (MSL) groups
0 tens of thousands of feet ("0" means winds between 0 and 10,000 ft. MSL.)
0 sfc winds
2 2000' MSL winds
3 3000' MSL winds
12507 sfc winds 125/07 kts
14511 2000' winds 145 degrees/11 kts
18518 3000' winds 185 degrees/18 kts
90467 9 indicator for wind height groups
0 tens of thousands of feet ("0" means winds between 0 and 10,000 ft MSL.)
4 4,000' MSL winds
6 6,000' MSL winds
7 7,000' MSL winds
20015 4000' winds 200 degrees/15 kts
22507 6000' winds 225 degrees/7 kts
24509 7000' winds 245 degrees/9 kts
....................................................
9503/ 9 indicator for wind height groups
5 winds betwween 50,000' and 60,000' MSL follow
0 50,000' MSL winds
3 53,000' MSL winds
/ no more wind data between 50,000' and 60,000'
32536 50,000' winds 325 degrees/36 kts
32024 53,000' winds 320 degrees/24 kts
University of North Dakota / School of Aerospace Sciences / Atmospheric Science Department
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