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Measurement Descriptions and Units

STATION ID Five-digit WMO Station Identifier used since 1976. ID's can be reassigned to future deployments within the same 1 degree square.
DATE In UTC (formerly called Greenwich Mean Time - GMT)
TIME In UTC for data files/display. Station pages show current observations in station local time by default, but can be changed by the viewer to UTC. See the Acquisition Time help topic for a more detailed description of observation times.

Data are classified according to the following groups. Any data field that contains "9 filled" represents missing data for that observation hour. (Example: 999.0 99.0)

Standard Meteorological Data

ATMP Air temperature (Celsius). For sensor heights on buoys, see Hull Descriptions. For sensor heights at C-MAN stations, see C-MAN Sensor Locations
WTMP Sea surface temperature (Celsius). For sensor depth, see Hull Description.
DEWP Dewpoint temperature taken at the same height as the air temperature measurement.
PRES Sea level pressure (hPa). For C-MAN sites and Great Lakes buoys, the recorded pressure is reduced to sea level using the method described in NWS Technical Procedures Bulletin 291 (11/14/80).
WSPD Wind speed (m/s) averaged over an eight-minute period for buoys and a two-minute period for land stations. Reported Hourly. See Wind Averaging Methods.
WDIR Wind direction (the direction the wind is coming from in degrees clockwise from true N) during the same period used for WSPD. See Wind Averaging Methods
GST Peak 5 or 8 second gust speed (m/s) measured during the eight-minute or two-minute period. The 5 or 8 second period can be determined by payload, See the Sensor Reporting, Sampling, and Accuracy section.
WVHT Significant wave height (meters) is calculated as the average of the highest one-third of all of the wave heights during the 20-minute sampling period. See the Wave Measurements section.
APD Average wave period (seconds) of all waves during the 20-minute period. See the Wave Measurements section.
DPD Dominant wave period (seconds) is the period with the maximum wave energy. See the Wave Measurements section.
MWD Mean wave direction corresponding to energy of the dominant period (DOMPD). The units are degrees from true North just like wind direction. See the Wave Measurements section.
VIS Station visibility (statute miles). Note that buoy stations are limited to reports from 0 to 1.9 miles.
PTDY Pressure Tendency is the direction (plus or minus) and the amount of pressure change (hPa)for a three hour period ending at the time of observation.
TIDE The water level in feet above or below Mean Lower Low Water (MLLW).

Derived Met Values

HEAT For more information on heat index, please see the NWS Heat Wave page.
CHILL Please note that NDBC uses unadjusted winds to calculate wind chill. The winds are calculated at anemometer height. For more information on wind chill, please see the NWS Wind Chill Temperature Index.
ICE Estimated ice accretion in inches per hour based on an algorithm developed by Overland and Pease at the Pacific Marine Environmental Laboratory in the mid-1980s. The algorithm relates icing to the presently observed wind speed, air temperature, and sea surface temperature. The method is designed for trawlers in the 20 to 75 meter length range, underway at normal speeds in open seas and not heading downwind. In general, NWS forecasters translate ice accretion rates to the following categories:
  • light: 0.0 to 0.24 inches of ice accretion/hour;
  • moderate: 0.25 to 0.8 inches/hour; and
  • heavy: greater than 0.8 inches/hour.

Detailed Wave Summary

H0 Significant Wave Height is the average height (meters) of the highest one-third of the waves during a 20 minute sampling period.
SWH Swell height is the vertical distance (meters) between any swell crest and the succeeding swell wave trough.
SWP Swell Period is the time (usually measured in seconds) that it takes successive swell wave crests or troughs pass a fixed point.
SWD Swell Direction is the compass direction from which the swell wave are coming from.
WWH Wind Wave Height is the vertical distance (meters) between any wind wave crest and the succeeding wind wave trough (independent of swell waves).
WWP Wind Wave Period is the time (in seconds) that it takes successive wind wave crests or troughs to pass a fixed point.
WWD Wind Wave Direction is the compass direction (degrees) from which the wind waves are coming.
Steepness Wave steepness is the ratio of wave height to wave length and is an indicator of wave stability. When wave steepness exceeds a 1/7 ratio; the wave becomes unstable and begins to break.
AVP Average Wave Period is the average period (seconds) of the highest one-third of the wave observed durng a 20 minute sampling period.
MWD Mean wave direction corresponding to energy of the dominant period (DOMPD). The units are degrees from true North just like wind direction. See the Wave Measurements section.

Acoustic Doppler Current Profiler (ADCP)

DEP01,DEP02,... The distance from the sea surface to the middle of the depth cells, or bins, measured in meters.
DIR01,DIR02,... The direction the ocean current is flowing toward. 0-360 degrees, 360 is due north, 0 means no measurable current.
SPD01,SPD02,... The speed of the ocean current measured in cm/s.

Continuous Winds

DIR Ten-minute average wind direction measurements in degrees clockwise from true North.
SPD Ten-minute average wind speed values in m/s.
GDR Direction, in degrees clockwise from true North, of the GSP, reported at the last hourly 10-minute segment.
GSP Maximum 5-second peak gust during the measurement hour, reported at the last hourly 10-minute segment.
GMN The minute of the hour that the GSP occurred, reported at the last hourly 10-minute segment.

For more information on continuous winds and the timing of these measurements, see the continuous winds help section.

Spectral Wave Data

Spectral wave density Energy in (meter*meter)/Hz, for each frequency bin (typically from 0.03 Hz to 0.40 Hz).
Spectral wave direction Mean wave direction, in degrees from true North, for each frequency bin. A list of directional stations is available.
Directional Wave Spectrum = C11(f) * D(f,A), f=frequency (Hz), A=Azimuth angle measured clockwise from true North to the direction wave is from.
D(f,A) = (1/PI)*(0.5+R1*COS(A-ALPHA1)+R2*COS(2*(A-ALPHA2))), in which R1 and R2 are nondimensional and ALPHA1 and ALPHA2 are respectively mean and principal wave directions.
In terms of Longuet-Higgins Fourier Coefficients
  • R1 = (SQRT(a1*a1+b1*b1))/a0
  • R2 = (SQRT(a2*a2+b2*b2))/a0
  • ALPHA1 = 270.0-ARCTAN(b1,a1)
  • ALPHA2 = 270.0-(0.5*ARCTAN(b2,a2)+{0. or 180.})

For more information on the mathematics behind the measuring of surface water waves, see the waves help section.

Water Level

TG01, TG02,...,TG10 Six-minute water levels representing the height, in feet, of the water above or below Mean Lower Low Water (MLLW). Please subtract 10 ft. from every value to obtain the true water level value.

Marsh-McBirney Current Measurements

DIR Direction the current is flowing TOWARDS, measured in degrees clockwise from North.
SPD Current speed in cm/s.

Oceanographic Data

Salinity (SAL) Conductivity is measured and converted to salinity by a known functional relationship between the measured electrical conductivity of seawater temperature and pressure.

DART Measurements

T (TYPE) Measurement Type:
  • 1 = 15 minute measurement;
  • 2 = 1 minute measurement; and
  • 3 = 15 second measurement.
HEIGHT Height of water column in meters.
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