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=+28.5ø C, 1285=-28.5ø C
20253 DEW POINT TEMPERATURE 0253=+25.3ø C, 1253=-25.3ø 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
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217100 6th OLDEST 10-MIN CONT. WIND 217=217ø, 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
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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 Organization’s 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. |
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| 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. |
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| 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 – 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. View the resulting spectrum described in Section 00.
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.
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