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Plateau du Four wave buoy daily means for May 2025

Daily means from the Plateau du Four wave buoy for May 2025, including available wave height, period, direction, wind and sea temperature data.

Last observation shown

Data available:  to 

Monthly means for

Latest

Period Summary

Programmatically generated summary. Hog Says

1,488 wave-buoy observations covered all 31 days. Typical wave height was 2.2 ft (10th–90th percentile 1.5–4 ft), while mean peak wave period was 7.5 seconds (10th–90th percentile 3.3–11 seconds). Typical calculated wave power was approximately 1.3 kW/m (10th–90th percentile 0.6–4.5 kW/m), derived from significant wave height and energy period. 18 of 4,464 checked values (0.4%) were excluded by quality control. Across 15 comparable years, mean wave height was below the same-month mean of 3.3 ft and mean wave period was below the same-month mean of 8.2 seconds.

Generated only from the observations and comparisons shown on this page.

Typical Significant Wave Height

2.2ft
Mean: 2.4 ft
P10–P90: 1.5 — 4 ft
Recorded extremes

0.5 — 5.2 ft

Mean Observed Wave Period

7.5secs
P10–P90: 3.3 — 11secs
Recorded extremes

2.3 — 16.1secs

Available for 742 of 744 hourly samples

Typical Wave Power

Approximately 1.26kW/m
Mean: 1.84kW/m
P10–P90: 0.55 — 4.5kW/m
Recorded extremes

0.07 — 7.54kW/m

Calculated from significant wave height and energy period.

Typical Observed Wind

-, -mph
Mean: - mph
P10–P90: - — - mph

Available for 0 of 744 hourly samples

Mean Water Temperature

-°C
P10–P90: - — -°C

Available for 0 of 744 hourly samples

Compared With Previous Mays

Historical baseline from 21,206 observations across 15 years.

Wave Height
2.4ft
0.9ft below mean
Historical mean 3.314ft
Wave Period
7.5s
0.7s below mean
Historical mean 8.2s
Water Temperature
–
Not enough comparable data

Chart showing grouped wave observations for Plateau du Four. Use the table on this page for a text version of the same measurements. To open hourly observations, use a linked day name in the table.

About Plateau du Four wave buoy

Plateau du Four is a CANDHIS station associated with the SEM-REV offshore test site off Loire-Atlantique. Located near a shallow offshore bank west of Le Croisic, it supplies environmental context for marine-energy research and for an exposed sector between the Loire estuary and southern Brittany.

Its current data source reports wave height, wave period, wave direction, directional spread and sea temperature.

Metrics are rows; days run left to right.
Plateau du Four wave buoy daily means May 2025Last observation shown
Metric
Mean significant wave height (ft)2223322222243222222233224444223
Mean maximum wave height (ft)3334543223355333333345437676435
Mean peak period (s)712116433548117795681189976651099999
Mean average period (s)5785433335576644675656555867887
Mean period Tm02 (s)4554333334455533544444444655675
Mean peak wave directionSWconcentration 78%Wconcentration 98%WSWconcentration 94%Nconcentration 53%NNEconcentration 100%NNEconcentration 99%NEconcentration 99%NNEconcentration 59%NNEconcentration 83%WNWconcentration 38%Wconcentration 100%SWconcentration 98%WSWconcentration 96%Wconcentration 99%NNWconcentration 60%Nconcentration 62%WNWconcentration 47%Wconcentration 100%Wconcentration 59%Wconcentration 95%Wconcentration 90%Wconcentration 98%Wconcentration 99%Wconcentration 99%Wconcentration 99%Wconcentration 100%Wconcentration 100%Wconcentration 100%Wconcentration 100%Wconcentration 100%Wconcentration 100%
Mean directional spread (°)26.228.128.628.322.623.428.230.628.728.030.330.731.632.529.326.628.226.530.227.929.524.426.126.925.520.225.626.825.423.822.0
Mean water temperature(°C)-------------------------------

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Wave metric colour key

Colours move through the scale as each number increases. They do not by themselves mean that conditions are good, safe or suitable for you.

Wave & swell height0–40+ ft
Wave & swell period0–22+ s
Wind speed0–75 mph

The displayed numbers remain the source of truth; colour is an additional visual cue.

What does buoy wave power mean?

kW/m means kilowatts of wave power per metre of wave crest. It describes the rate at which the observed sea state carries energy past the buoy.

Unlike the shore-directed forecast value, buoy wave power is the total power at the observation point. It is not projected towards a particular beach and does not predict breaking wave height.

In deep water, wave power can be calculated with:

P is approximately 0.49 times significant wave height squared times wave energy period.

P is power in kW/m, Hs is significant wave height in metres, and Te is wave energy period in seconds.

  • Provider-reported power is used when available.
  • Otherwise, a value is calculated only when both significant height and a genuine energy period are available. The ≈ symbol marks calculated values.
  • A dash is shown instead of substituting peak, Tm02, zero-crossing or other period measurements.
  • Daily and monthly figures use the mean of hourly-normalized observation power values; they are not calculated from mean height and period.

Wave direction, spectrum, water depth and local bathymetry still matter. Wave power is best read alongside height, period and direction rather than as a standalone surf-quality score.

The observation data displayed on this page is from the Cerema CANDHIS coastal wave observatory.

Learn how SurfHog combines, checks and summarizes observations in the data and methodology notes.

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