National Data Buoy Center

Data is for ALL of 2008 and hourly


Data Descriptions

Notes:
Not all sations have the data listed below.
Water levels are referenced to MLLW

Standard Meterological Data
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
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.
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.
DPD 	Dominant wave period (seconds) is the period with the maximum wave energy. See the Wave Measurements section.
APD 	Average wave period (seconds) of all waves during the 20-minute period. See the Wave Measurements section.
MWD 	Mean wave direction corresponding to energy of the dominant period (DPD). The units are degrees from true North just like wind direction. See the Wave Measurements section.
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).
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.
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). 


Detailed Wave Summary
WVHT 	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.
APD 	Average Wave Period is the average period (seconds) of the highest one-third of the wave observed during 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.


Spectral Wave Data
Sep_Freq 	The Separation Frequency is the frequency that separates wind waves (WWH, WWP, WWD) from swell waves (SWH, SWP,SWD). NDBC inserts the value 9.999 if Sep_Freq is missing.
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))). R1 and R2 are the first and second normalized polar coordinates of the Fourier coefficients and are nondimensional. ALPHA1 and ALPHA2 are respectively mean and principal wave directions.
In terms of Longuet-Higgins Fourier Coefficients