Significant Wave Height Explained
Learn what this widely used wave statistic represents, how it is estimated and why individual waves can be substantially higher.
Illustrative sea state, not a measured buoy frame. Significant wave height is a statistical summary of a sample, not the height of the single wave shown.
The average of the highest one-third
Significant wave height is the mean height of the highest one-third of waves in a measured or modeled sample. Buoys estimate it from a time series of sea-surface motion; models calculate it from the wave-energy spectrum.
It approximates the wave height an experienced observer tends to perceive, but it is not the maximum wave. Individual waves can be considerably higher.
Read height with period, direction and swell
Local wind creates wind sea, while swell can travel far from its generating storm. The same significant height can feel very different depending on wave period, direction, currents, bathymetry and vessel or coastal exposure. Use current official marine forecasts and warnings for decisions.
From evidence to the PlanetVexa view
Each stage changes what can be claimed. PlanetVexa keeps the source record, derived interpretation and visual presentation visibly distinct.
- 01Sea-surface motion
A buoy or model represents changing elevation and wave energy through time.
- 02Quality control
Instrument motion, sampling and station status are checked before use.
- 03Wave statistic
The highest one-third of waves in the sample contributes to significant wave height.
- 04PlanetVexa record
Height, period, wind, station, timestamp and source context remain separate fields.
Height alone is not the sea state
Compare significant height with dominant period, wave direction, swell and local wind. Long-period swell and short wind sea can affect a vessel or coastline very differently at the same height.
PlanetVexa keeps station time and measurement fields visible. It does not convert a buoy observation into a local safety recommendation away from that station.
Current Ocean Signal
Live records refresh independently from this article. Source time and freshness never change the editorial “Last updated” date above.
Source: NOAA National Data Buoy Center · Freshness: Fresh · Live data updated · source details
Explore Ocean ConditionsUse source time, definitions and official guidance
PlanetVexa explains and normalizes source-backed information for general understanding. Values can be revised, observations can be incomplete, and a global or statistical measure cannot replace local analysis or official safety guidance.
FAQ
Is significant wave height the largest wave?
No. It is an average of the highest one-third, and individual waves can be larger.
Why does wave period matter?
Longer-period waves carry energy differently and can produce different vessel and coastal effects at the same height.
Read the official material
Definitions and operational context are checked against the responsible institutions. External material can be revised independently of PlanetVexa.