Significant wave height

SWHwave height
In physical oceanography, the significant wave height (SWH or H s ) is defined traditionally as the mean wave height (trough to crest) of the highest third of the waves (H 1/3 ).wikipedia
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Wave height

trough to crestwave heightsheight
is defined traditionally as the mean wave height (trough to crest) of the highest third of the waves (H 1/3 ).
At sea, the term significant wave height is used as a means to introduce a well-defined and standardized statistic to denote the characteristic height of the random waves in a sea state.

Wind wave

waveswaveocean wave
is defined traditionally as the mean wave height (trough to crest) of the highest third of the waves (H 1/3 ).
For weather reporting and for scientific analysis of wind wave statistics, their characteristic height over a period of time is usually expressed as significant wave height.

Rogue wave

freak waverogue wavesfreak waves
In oceanography, rogue waves are more precisely defined as waves whose height is more than twice the significant wave height (H s or SWH), which is itself defined as the mean of the largest third of waves in a wave record.

Sea state

sea state 6rough seasSea State 3
A sea state is characterized by statistics, including the wave height, period, and power spectrum.

Wind wave model

WAMocean wave modelsforecasts
RSMCs use wind-wave models as tools to help predict the sea conditions.
Results are typically summarized by the significant wave height, which is the average height of the one-third largest waves, and the period and propagation direction of the dominant wave.

Physical oceanography

physical oceanographerphysicaloceanographic
In physical oceanography, the significant wave height (SWH or H s )

Crest and trough

cresttroughwave crest
is defined traditionally as the mean wave height (trough to crest) of the highest third of the waves (H 1/3 ).

Standard deviation

standard deviationssample standard deviationSD
Nowadays it is usually defined as four times the standard deviation of the surface elevation – or equivalently as four times the square root of the zeroth-order moment (area) of the wave spectrum.

Area

surface areaArea (geometry)area formula
Nowadays it is usually defined as four times the standard deviation of the surface elevation – or equivalently as four times the square root of the zeroth-order moment (area) of the wave spectrum.

Spectral density

frequency spectrumpower spectrumspectrum
Nowadays it is usually defined as four times the standard deviation of the surface elevation – or equivalently as four times the square root of the zeroth-order moment (area) of the wave spectrum.

Walter Munk

Walter Heinrich MunkWalter H. MunkDr. Walter Munk
The original definition resulted from work by the oceanographer Walter Munk during World War II.

Rayleigh distribution

RayleighRayleigh distributeddistribution
Generally, the statistical distribution of the individual wave heights is well approximated by a Rayleigh distribution.

Root mean square

RMSroot-mean-squarequadratic mean
The RMS wave height, which is defined as square root of the average of the squares of all wave heights, is approximately equal to H s divided by 1.4.

World Meteorological Organization

WMOWorld Meteorological OrganisationESCAP/WMO Typhoon Committee
The World Meteorological Organization stipulates that certain countries are responsible for providing weather forecasts for the world's oceans.

Regional Specialized Meteorological Center

Regional Specialized Meteorological CentreTropical Cyclone Warning CentreRegional Specialised Meteorological Centre
These respective countries' meteorological offices are called Regional Specialized Meteorological Centers, or RSMCs.

National Weather Service

United States Weather BureauWeather BureauU.S. Weather Bureau
In the United States, NOAA's National Weather Service is the RSMC for a portion of the North Atlantic, and a portion of the North Pacific.

Ocean Prediction Center

Marine Prediction CenterNational Weather Service Ocean Prediction Center
The Ocean Prediction Center and the Tropical Prediction Center's Tropical Analysis and Forecast Branch (TAFB) issue these forecasts.

National Hurricane Center

National Hurricane Center (NHC)NHCNational Hurricane
The Ocean Prediction Center and the Tropical Prediction Center's Tropical Analysis and Forecast Branch (TAFB) issue these forecasts.

Sevenstones Lightship

Sevenstones'' LightshipSevenstones Lightvessellightvessel
A series of Trinity House lightships stationed near the Sevenstones Reef have measured significant wave heights (Hs or SWH)—the periodic average of the highest one third of waves in a spectrum—since the early 1960s using Ship Borne Wave Recorders (SBWR).

Wave power

wave energywavewaves
with P the wave energy flux per unit of wave-crest length, H m0 the significant wave height, T e the wave energy period, ρ the water density and g the acceleration by gravity.

1991 Perfect Storm

Perfect Storm1991 Halloween Nor'easterPerfect Storm of 1991
East of Cape Cod, a NOAA buoy located at 41.1°N, -66.6°W reported maximum sustained winds of 56 mph with gusts to 75 mph, and a significant wave height (average height of the highest one-third of all waves) of 39 ft around 15:00 UTC on October 30.

Rockall Basin

Rockall TroughRockall PlateauHatton-Rockall Basin
In February 2000, the RRS Discovery, a British oceanographic research vessel sailing in the Rockall Trough encountered the largest waves ever recorded by scientific instruments in the open ocean, with a SWH of 18.5 m and individual waves up to 29.1 m.

MS Estonia

MS ''EstoniaEstoniaM/S Estonia
According to the final disaster report, the weather was rough, with a wind of 15 to 20 m/s, force 7–8 on the Beaufort scale and a significant wave height of 4 to 6 m compared with the highest measured significant wave height in the Baltic Sea of 7.7 m. Esa Mäkelä, the captain of Silja Europa who was appointed on-scene commander for the subsequent rescue effort, described the weather as "normally bad", or like a typical autumn storm in the Baltic Sea.