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How do you decode real-time data?

DECODING BUOY METEOROLOGICAL DATA

The following is an example of a NDBC buoy observation in FM-13 code.

42003 28121 99259 70859 46/// /2211 10285 20253 30091 40091
57012 91150 22200 00289 10603 20502 318// 41201 70013 333 91213
555 11107 22114 31127 42314 50083 61149 223113 225107 219111
228116 227103 217100 71105 82012 91110=

The decoding follows:

42003     STATION IDENTIFIER             First two numbers indicate WMO region.

28121     TIME AND WIND UNITS            28=Day, 12=hour(UTC), 1=measured speed in m/s.

99259     LATITUDE                       25.9 degrees (in this case N latitude)

70859     LONGITUDE & QUADRANT           7=quadrant of globe that buoy is located,
                                         where
                                            1= N latitude & E longitude
                                            3= S latitude & E longitude
                                            5= S latitude & W longitude
                                            7= N latitude & W longitude

                                         0859= 85.9 W longitude

/2211     WIND DIRECTION & SPEED         Wind blowing from 220 degrees at 11 m/s

10285     AIR TEMPERATURE                0285=+28.5° C, 1285=-28.5° C

20253     DEW POINT TEMPERATURE          0253=+25.3° C, 1253=-25.3° C

30113     STATION BARO. PRESSURE         30113=1011.3 hPa, 39995=999.5 hPa

40113     SEA LEVEL PRESSURE             40113=1011.3 hPa, 49995=999.5 hPa

57012     3 HR. PRESSURE TENDENCY        Pressure 1.2 hPa lower than three hours ago

91150     END OF ACQUISITION TIME        The end of data acquisition=1150 UTC

00289     SEA WATER TEMPERATURE          0289=+28.9 C, 1010=-1.0 C

10603     SEA STATE                      Dominant period=6 sec., Wave height=3 half meters

20502     WIND WAVE HEIGHT & PERIOD      The wind-wave height is one-meter (02 = 2 half-meters)
                                         and wind-wave period is 5 seconds.

318//     PRIMARY SWELL DIRECTION        The primary swell direction = 180 deg. (from the south); 
                                         only buoys reporting directional waves encode this group.

41201     SWELL HEIGHT & PERIOD          The swell height is a half-meter (01 = one half-meter)
                                         and the primary swell period is 12 seconds.

70013     WAVE HEIGHT                    Significant wave height= 1.3 meters
                                         (higher precision)

91213     PEAK WIND GUST                 5-sec. peak wind during 8-minute
                                         acquisition interval=13 m/s.

11107     WIND AT 10 METERS              Estimated wind at 10 meters elevation=10.7 m/s.

22114     WIND AT 20 METERS              Estimated wind at 20 meters elevation=11.4 m/s.

31127     TIME OF PEAK 5-SEC WIND        11=UTC hour, 27=minutes after the hour

42314     5-SEC PEAK WIND SPD/DIR        23=230 degrees, 14=14 meters/sec.

50083     LOWEST ONE-MINUTE PRESSURE     0083= 1008.3 hPa

61149     TIME OF CONTINUOUS WIND        1149=end time in hours and minutes (UTC) of
                                         latest 10-minute continuous wind.

223113    LATEST 10-MIN CONT. WIND       223=223 degrees, 113=11.3 m/s

225107    NEXT OLDER 10-MIN CONT. WIND   225=225 degrees, 107= 10.7 m/s
                    "
                    "
                    "
217100    6th OLDEST 10-MIN CONT. WIND   217=217°, 100=10.0 m/s

71105     TIME OF LOWEST PRESSURE        time of lowest 1-min press = 1105 UTC.

82012     ONE-MINUTE PEAK WIND           2012= 200 degrees at 12 m/s.

91110     TIME OF 1-MINUTE PEAK WIND     time of 1-min peak wind = 1110 UTC.

NOTE: Some groups may not be included in an individual message.

DECODING C-MAN METEOROLOGICAL DATA

The following is an example of an NDBC C-MAN observation in code.

CMAN 20124
DSLN7 46/// /0113 10110 20095 40292 52021 91200 222// 00204 10703
70016 333 91218 555 11012 22012 31135 402021 61159 005012 022011
008012 007012 011011 007012 TIDE1157=

The decoding follows:

CMAN      Heading indicating that the following stations are Coastal Marine Stations

20124     TIME AND WIND UNITS            20=day of month, 12=1200 UTC, 4=wind in knots

DSLN7     STATION IDENTIFIER             Diamond Shoals Light, NC

/0113     WIND DIR. & SPEED              Wind blowing from 010 at 13 knots

10110     AIR TEMPERATURE                0110=11.0C, 1110=-11.0C

20095     DEW POINT TEMP.                0095=9.5C, 1095=-9.5C

40292     SEA LEVEL PRESSURE             40292=1029.2 hPa, 49995=999.5 hPa

52021     3hr. PRESS. TENDENCY           Pressure 2.1 hPa higher than 3 hrs ago

91200     END OF ACQ. TIME               end of data acquisition=1200 UTC

00204     SEA WATER TEMP.                0204=20.4C, 1204=-20.4C

10703     SEA STATE                      dominant period=7 sec., wave hgt=3 half meters

70016     REFINED SEA STATE              hgt of highest 1/3 waves=1.6 meters

91218     PEAK WIND GUST                 highest peak wind gust=18 knots

11012     WIND SPD AT 10m                wind speed at 10m above site elev.=12 knots

22012     WIND SPD AT 20m                wind speed at 20m above site elev.=12 knots

31135     TIME OF MAX WIND SPEED         11=11 UTC, 35=35 min. after the hr.

402021    MAX WIND SPEED & DIR.          020=20 degrees, 21=21 knots

61159     TIME OF CONT. WIND             1159=end time in hours and minutes (UTC) of
                                         latest 10-minute continuous wind.

005012    LATEST 10-MIN CONT. WIND       005=5 degrees, 012= 12 knots

022011    NEXT OLDER 10-MIN CONT WIND    022=22 degrees, 011=11 knots

                    "
                    "
                    "
007012    6th OLDEST CONTINUOUS WIND     007=7 degrees, 012=12 knots

TIDE1157  TIDAL HEIGHT                   tidal height is 1.57 feet above
                                         Mean Lower Low Water (MLLW)

Note: Some groups may not be included in an individual message.

 

DECODING SPECTRAL WAVE DATA

NDBC distributes spectral wave data using the WMO FM 65-XI WAVEOB alphanumeric code. Because of the complexity of the code, users should consult the World Meteorological Organizationĺs Manual on Codes, WMO-No. 306. The example below illustrates the content of information available in the code rather than a guide to decoding.

SXVX46 KWBC 310100 RRC
MMXX 46063 31018 0100/ 73416 12042
00011 10632 20296 30114 50062 975//
11146 0006/ 2400/ 13/// 13254 15003 26/// 21005 21004 07/// 33655
32004
22226 94312 10000 30000 51200 70221 91526 18700 35535 52410 72628
94857 15730 31314 50906 71204 90506 10403 30303 50301 70101 90101
10000 30000 50000
4444 19999 19999 29999 29999 39999 39999 49999 49999 57377 52539
69999 69999 78385 74664 85536 82748 97475 94442 07275 05460
17777 18986 27576 28984 37778 38677 47676 48981 57777 58468
67576 68360 77676 79178 87474 88661 97575 99484 07575 09273
17980 19277 27676 29272 37878 38764 47778 48969 57777 58658
67677 68036 77879 79169 87777 88461 97878 98655 07878 08349
17777 18759 27573 28038 37980 37835 47877 47634 57574 57623
68081 66515 77981 77624 87777 88052 97370 97322 07368 07236
18208 15621 27265 26739 37469 37230 49999 49999 59999 59999
69999 69999
MMXX REPORT IDENTIFIER MMXX indicates FM 65-XI WAVEOB.
46063 STATION IDENTIFIER First two numbers indicate WMO region.
31018 DATE AND TIME OF THE REPORT 31 = 31st day of the month. 01 = month of the year. 8 = Year 2008.
0100/ HOUR AND MINUTE OF THE REPORT 0100 = 0100 UTC.
73416 LATITUDE 7 = Quadrant of the globe indicating north of the equator and west of the Greenwich meridian.
1 = N latitude & E longitude, 3 = S latitude & E longitude,
5 = S latitude & W longitude
7 = N latitude & W longitude.
Thus, 3416 = 34.16░ North Latitude.
12042 LONGITUDE 12042 = 120.42░ West (given by quadrant indicator in previous group) Longitude.
00011 SECTION 00, WAVE CHARACTERISTICS INDICATORS 00 = Section indicator. 011 indicates:
0 = Indicates the spectrum is in frequency rather than wavenumber.
1 = Indicates that the method of calculation of the spectral data is Longuet-Higgins (1964).
1 = Indicates that the platform type is an automatic data buoy.
10632 DEPTH OF THE WATER 0632 = 632 meters water depth.
20296 SIGNIFICANT WAVE HEIGHT 296 = 296 cm or 2.96 m.
30114 DOMINANT PERIOD 0114 = 11.4 seconds.
50062 AVERAGE PERIOD 0062 = 6.2 seconds.
975// WAVE DIRECTION AT THE DOMINANT PERIOD IN 4-DEGREE INCREMENTS 75 = Waves are coming from 298░ to 300░ True.
11146 SECTION 111, NUMBER OF FREQUENCIES 111 = Section Indicator
46 = 46 frequencies in the spectrum.
0006/ SAMPLING INTERVAL 0006 = indicates 0.6 seconds between samples.
2400/ DURATION OF THE WAVE RECORD 2400 = 2400 seconds.
13/// THE NUMBER OF FREQUENCY BANDS DESCRIBED IN THE NEXT TWO GROUPS 13 = The first 13 frequency bands.
13254 CENTER FREQUENCY OF THE FIRST BAND DESCRIBED IN THIS GROUP 3254 = 0.0325 Hz.
15003 INCREMENT ADDED TO OBTAIN NEXT CENTER FREQUENCY 5003 = indicates 0.005 Hz to be added to the previous center frequency to obtain the each successive center frequency in the group.
26/// THE NUMBER OF FREQUENCY BANDS DESCRIBED IN THE NEXT TWO GROUPS 26 = The next 26 frequency bands.
21005 CENTER FREQUENCY OF THE FIRST BAND DESCRIBED IN THIS GROUP 1005 = 0.01 Hz.
21004 INCREMENT ADDED TO OBTAIN NEXT CENTER FREQUENCY 1004 = indicates 0.010 Hz to be added to each the previous center frequency to obtain the each successive center frequency in the group. 4 = indicates the index to a lookup table for the exponent.
07/// THE NUMBER OF FREQUENCY BANDS DESCRIBED IN THE NEXT TWO GROUPS 07 = The next 7 frequency bands.
33655 CENTER FREQUENCY OF THE FIRST BAND DESCRIBED IN THIS GROUP 3655 = 0.365 Hz.
32004 INCREMENT ADDED TO OBTAIN NEXT CENTER FREQUENCY 2004 = indicates 0.020 Hz to be added to each the previous center frequency to obtain the each successive center frequency in the group.
22226 INDICATOR OF THE NONDIRECTIONAL SPECTRAL DENSITY SECTION 2222 = Section Indicator 6 = Code figure to indicate exponent for spectral wave data where 6 represents 101.
94312 MAXIMUM VALUE FOR NONDIRECTIONAL SPECTRA 943 = 9.43 m2/Hz (decimal point is assumed to be at the start of the numeric values.
12 = indicates frequency band 12 has the maximum spectral density.
10000 30000 51200 70221 91526 18700 35535 52410 72628 94857 15730 31314 50906 71204 90506 10403 30303 50301 70101 90101 10000 30000 50000 These groups contain the spectral density values expressed as a percentage of the maximum value provide in the previous group (94312). Each group contains values for 2 frequencies. 00 may indicate less than 0.5% or 100% (00 in 18700 is the 100% value ľ frequency number 12).
4444 DIRECTIONAL WAVE FUNCTIONS SECTION INDICATOR The groups to follow contain directional wave information.
19999 19999 29999 29999 39999 39999 49999 49999 57377 52539 69999 69999 78385 74664 85536 82748 97475 94442 07275 05460 17777 18986 27576 28984 37778 38677 47676 48981 57777 58468 67576 68360 77676 79178 87474 88661 97575 99484 07575 09273 17980 19277 27676 29272 37878 38764 47778 48969 57777 58658 67677 68036 77879 79169 87777 88461 97878 98655 07878 08349 17777 18759 27573 28038 37980 37835 47877 47634 57574 57623 68081 66515 77981 77624 87777 88052 97370 97322 07368 07236 18208 15621 27265 26739 37469 37230 49999 49999 59999 59999 69999 69999 The first digit is counter to a corresponding frequency. Two successive groups apply to a single frequency. The first group contains the mean wave direction and principal wave direction expressed in 4-degree codes. The second group contains the first and second normalized polar coordinates from the Fourier coefficients.

The above is an example of the code for a directional wave station. For a nondirectional wave station, Section 4444 and the 9-Group of Section 00 (975//) are omitted. The above is an example from a (D)WPM wave system. To see the resulting spectrum described in Section 00, click here.

A (D)WA system would be described as:

11133 0005/ 1200/ 33/// 13004 11004

33 frequencies (11133)
0.5-second sampling interval (0005/)
1200 seconds for sampling duration (1200/)
The first of the 33 frequencies (33///) starts at 0.030 Hz (13004) and each subsequent frequency is at a 0.01 Hz interval (11004). Even though a DWA system has 38 frequency bands of nondirectional spectral densities, only the first 33 bands are provided in the FM 65.