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Plateau du Four wave buoy daily means for Apr 2021

Daily means from the Plateau du Four wave buoy for Apr 2021, 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

1,440 wave-buoy observations covered all 30 days. Typical wave height was 2.1 ft (10th–90th percentile 1.2–3.5 ft), while mean average of more than one wave period type was 6.8 seconds (10th–90th percentile 3.3–11.6 seconds). Typical calculated wave power was approximately 1.2 kW/m (10th–90th percentile 0.4–2.9 kW/m), derived from significant wave height and energy period. 19 of 4,306 checked values (0.4%) were excluded by quality control. Across 11 comparable years, mean wave height was below the same-month mean of 3.8 ft and mean wave period was below the same-month mean of 9.2 seconds.

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

Typical Significant Wave Height

2.1ft
Mean: 2.3 ft
P10–P90: 1.2 — 3.5 ft
Recorded extremes

0.7 — 7.6 ft

Mean Observed Wave Period

6.8secs
P10–P90: 3.3 — 11.6secs
Recorded extremes

2.2 — 18.2secs

Typical Wave Power

Approximately 1.17kW/m
Mean: 1.9kW/m
P10–P90: 0.37 — 2.86kW/m
Recorded extremes

0.19 — 32.05kW/m

Calculated from significant wave height and energy period.

Available for 717 of 720 hourly samples with wave power

Typical Observed Wind

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

Available for 0 of 720 hourly samples

Mean Water Temperature

-°C
P10–P90: - — -°C

Available for 0 of 720 hourly samples

Compared With Previous Aprils

Historical baseline from 15,837 observations across 11 years.

Wave Height
2.3ft
1.5ft below mean
Historical mean 3.773ft
Wave Period
6.8s
2.4s below mean
Historical mean 9.2s
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 Apr 2021Last observation shown
Metric
Mean significant wave height (ft)334222111232233222222224QC rejected42222
Mean maximum wave height (ft)456333222342354333334346963433
Mean peak period (s)1154764759547344661111101177101346485
Mean average period (s)9444445564463444489109458944454
Mean period Tm02 (s)644333445345333335686446644343
Mean peak wave directionWconcentration 100%NNEconcentration 72%NEconcentration 99%NNWconcentration 44%WNWconcentration 81%Nconcentration 82%Wconcentration 71%SSEconcentration 62%SWconcentration 94%WSWconcentration 56%NNWconcentration 91%Wconcentration 73%ENEconcentration 83%ENEconcentration 98%NEconcentration 99%Nconcentration 44%NNWconcentration 50%Wconcentration 100%Wconcentration 100%WSWconcentration 100%Wconcentration 100%Variableconcentration 12%Variableconcentration 21%Variableconcentration 27%WSWconcentration 100%NEconcentration 89%NWconcentration 42%WNWconcentration 89%Wconcentration 91%Nconcentration 59%
Mean directional spread (°)23.625.724.229.929.030.932.829.328.235.933.134.232.033.628.428.629.123.823.920.822.534.826.325.822.429.927.929.829.930.3
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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