Caption: Time series of Max Wave (m) showing the tallest individual wave recorded during each hourly 17.5-min measurement window. Hourly data (200k observations) - no daily averaging to preserve full detail. The highest Max Wave (29.9 m) was recorded at M6 on 2020-10-28 03:00 UTC (zoom to this date to see it). M6 (deep Atlantic, 3000m depth) typically shows larger waves due to open ocean exposure.
Caption: Time series of Signif Wave (m) showing the mean of the highest 1/3 of waves measured during each hourly 17.5-min window. Hourly data (200k observations) - no daily averaging to preserve full detail. This metric smooths out individual wave variability while capturing sea state severity. Max Signif Wave: 15.8 m at M4 on 2022-02-21 03:00 UTC (zoom to this date). Clear seasonal pattern with higher values in winter (Oct-Mar).
Caption: Time series of Wind Speed (knots) showing the 10-minute average wind speed recorded each hour. Hourly data (200k observations) - no daily averaging to preserve full detail. Wind measurements are taken at ~3m above sea level. Gust speeds (not shown here) can be 40-60% higher. Strong correlation with Signif Wave (r = 0.609).
Caption: Wind Speed vs Signif Wave relationship for observations with wind >20 knots (strong wind conditions). Panels ordered by regression slope. The slope indicates wave height increase (m) per knot of wind. M6 (deep Atlantic) shows steepest slope due to unlimited fetch. Filtering for high winds focuses on storm conditions where wind-wave coupling is strongest.
mev::fit.gpd()For detailed methodology and threshold sensitivity analysis, see the Wave Analysis vignette.
| Variable | Display Name | Units | Definition |
|---|---|---|---|
hmax |
Max Wave | m | Tallest individual wave (crest-to-trough) during each 17.5-min hourly measurement window |
wave_height |
Signif Wave | m | Mean height of the highest 1/3 of waves (~35 of ~105 waves) during each 17.5-min hourly window. NOAA definition |
wave_period |
Wave Period | s | Average time between successive wave crests via zero-crossing analysis |
Key distinction: Max Wave is a single wave; Signif Wave is an average of the top ~35 waves (highest 1/3). Both come from the same 17.5-min measurement window each hour.
Wind Measurements:| Variable | Display Name | Units | Definition |
|---|---|---|---|
wind_speed |
Wind Speed | knots | 10-minute average wind speed measured each hour at ~3m above sea level |
gust |
Gust | knots | Peak 3-second wind speed recorded during the hour |
| Variable | Display Name | Units | Definition |
|---|---|---|---|
atmospheric_pressure |
Pressure | hPa | Barometric pressure at sea level. Low pressure (<1000 hPa) often indicates storm systems |
air_temperature |
Air Temp | C | Air temperature at buoy (~3m above sea) |
sea_temperature |
Sea Temp | C | Sea surface temperature |
| Statistic | Source Column | Definition |
|---|---|---|
| Max Wave (m) | hmax |
Highest hmax across all hours (largest single wave ever recorded in dataset) |
| Max Signif (m) | wave_height |
Highest wave_height across all hours (highest hourly “average of top 1/3” value) |
| Avg Signif (m) | wave_height |
Mean of all hourly wave_height values (typical sea state) |
| Avg Max Wave (m) | hmax |
Mean of all hourly hmax values (typical tallest wave per hour) |
| Avg Ratio | hmax / wave_height |
Mean ratio of Max Wave to Signif Wave. Typical: 1.5-1.9. >2.0 = rogue conditions |
Why different? Max Wave (m) and Max Signif (m) come from DIFFERENT columns: - Max Wave = largest hmax = one extreme wave - Max Signif = largest wave_height = one extreme hourly average
Example: A station might record Max Wave = 15.2m (one extreme individual wave) and Max Signif = 10.8m (one extreme hourly average of top 1/3 waves). These come from different measurement windows.
A rogue wave is an individual wave with height > 2× the Signif Wave (i.e., Wave Ratio > 2.0).
| Wave Ratio (Max Wave / Signif Wave) | Interpretation |
|---|---|
| 1.5 - 1.9 | Normal sea state |
| > 2.0 | Rogue wave - individual wave significantly exceeds average |
Rogue waves are rare but dangerous. They can appear without warning in otherwise moderate seas. The ratio helps identify when individual waves significantly exceed the average sea state.
Important: The raw ERDDAP data does NOT contain a rogue wave indicator. We CALCULATE the ratio ourselves: rogue_ratio = hmax / wave_height. If ratio > 2.0, we classify it as a rogue wave event.
A rogue wind (or extreme gust) is a gust > 1.8× the mean wind speed (i.e., Gust Ratio > 1.8).
| Gust Ratio (Gust / Wind Speed) | Interpretation |
|---|---|
| 1.3 - 1.6 | Normal conditions |
| > 1.8 | Rogue wind - gust significantly exceeds average |
High gust ratios indicate atmospheric instability, often from convective activity, frontal passages, or turbulent flow. Combined with rogue waves, these events represent the most dangerous marine conditions.
Important: Similarly, rogue winds are CALCULATED: gust_ratio = gust / wind_speed. If ratio > 1.8, we classify it as a rogue wind event.
| Scientific Term | Display Name | Definition |
|---|---|---|
| Hs, H1/3, Significant Wave Height | Signif Wave | Mean height of highest 1/3 of waves in a measurement window. Equivalent to 4× standard deviation (4σ) of sea surface elevation for narrow-band spectra. |
| Hmax, Maximum Wave Height | Max Wave | Tallest single wave (crest-to-trough) in measurement window |
This dashboard uses “Signif Wave” and “Max Wave” consistently instead of technical symbols (Hs, Hmax).
Each buoy samples the sea surface once per hour. At the top of each hour, a 17.5-minute measurement period begins. During this window, the buoy measures approximately 105 individual wave heights (assuming ~10s wave period).
Sampling limitation: The buoy does NOT measure continuously. Only the 17.5-min window is sampled; waves occurring in the remaining 42.5 minutes of each hour are not recorded. Source: Marine Institute ERDDAP metadata states “The sensor measures this for 17.5 minutes and then takes an average.”
From this 17.5-min sample:
hmaxwave_height (NOAA definition)Both Max Wave and Signif Wave come from the SAME 17.5-min window, reported at the same timestamp.
Wind measurements are taken at approximately 3 meters above sea level. Two distinct metrics are reported:
| Measurement | Averaging Period | Definition |
|---|---|---|
| Wind Speed | 10-minute average | Mean wind speed over a 10-minute period, measured once per hour |
| Gust | 3-second peak | Maximum 3-second average wind speed during the hour |
Gust Factor: The ratio of Gust to Wind Speed indicates atmospheric turbulence and stability:
| Gust Factor | Interpretation |
|---|---|
| 1.3 - 1.6 | Normal conditions |
| > 1.8 | Gusty/unstable conditions |
High gust factors often occur with convective activity, frontal passages, or flow over rough terrain/seas. Low pressure systems (<1000 hPa) frequently accompany extreme wind events.