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St Mary's Sound wave buoy daily means for Apr 2023

Daily means from the St Mary's Sound wave buoy for Apr 2023, 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

1,436 wave-buoy observations covered all 30 days. Typical wave height was 3.9 ft (10th–90th percentile 2.5–6.4 ft), while mean average of more than one wave period type was 8.4 seconds (10th–90th percentile 5.3–11.5 seconds). Typical wind was 0 mph and mean water temperature was 10.9°C (10th–90th percentile 10.8–11°C). 12 of 5,735 checked values (0.2%) were excluded by quality control. Across 6 comparable years, mean wave height was above the same-month mean of 3.6 ft and mean wave period was above the same-month mean of 7.5 seconds.

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

Typical Significant Wave Height

3.9ft
Mean: 4.1 ft
P10–P90: 2.5 — 6.4 ft
Recorded extremes

1.8 — 11.6 ft

Mean Observed Wave Period

8.4secs
P10–P90: 5.3 — 11.5secs
Recorded extremes

3.3 — 14.3secs

Available for 718 of 719 hourly samples

Observed Wave Direction

SW

Circular concentration: 49%

Mean Water Temperature

10.9°C
P10–P90: 10.8 — 11°C
Recorded extremes

10.6 — 11.6°C

Compared With Previous Aprils

Historical baseline from 4,246 observations across 6 years.

Wave Height
4.1ft
0.5ft above mean
Historical mean 3.6ft
Wave Period
8.4s
0.9s above mean
Historical mean 7.5s
Water Temperature
10.9°C
0.3°C above mean
Historical mean 10.6°C

Chart showing grouped wave observations for St Mary's Sound. 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 St Mary's Sound wave buoy

St Mary's Sound station lies between St Mary's and St Agnes in the Isles of Scilly. The National Network first deployed a Datawell Directional WaveRider here in May 2014, establishing a nearshore record for an archipelago exposed to Atlantic swell and important to local navigation and coastal management.

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

Metrics are rows; days run left to right.
St Mary's Sound wave buoy daily means Apr 2023Last observation shown
Metric
Mean significant wave height (ft)63444334556QC rejected5543345QC rejected4443454422
Mean maximum wave height (ft)956654478710127864468126665786544
Mean peak period (s)1110610111210767899810101186776986767810
Mean zero-crossing period (s)664555545555556555554555454555
Mean energy period (s)------------------------------
Mean reported period (s)-----55-5555556455554555454555
Mean wave power, kilowatts per metre------------------------------
Mean peak wave directionSWconcentration 96%WSWconcentration 92%SSEconcentration 63%Variableconcentration 25%WSWconcentration 81%WSWconcentration 74%WNWconcentration 48%SEconcentration 44%SSEconcentration 73%SWconcentration 75%SWconcentration 86%WSWconcentration 90%WSWconcentration 91%SWconcentration 94%WSWconcentration 82%Wconcentration 88%Wconcentration 72%ESEconcentration 34%ESEconcentration 99%ESEconcentration 99%ESEconcentration 83%SEconcentration 64%SWconcentration 91%SWconcentration 99%SEconcentration 69%SSEconcentration 81%Sconcentration 86%SWconcentration 100%SWconcentration 92%Wconcentration 91%
Mean directional spread (°)45.455.940.748.258.360.253.338.441.845.143.746.550.841.849.358.650.939.224.721.029.431.241.737.034.436.233.530.841.748.2
Mean reported wave direction---Variableconcentration 25%-Wconcentration 85%Wconcentration 79%-Sconcentration 76%SWconcentration 81%SWconcentration 88%WSWconcentration 92%WSWconcentration 91%SWconcentration 95%WSWconcentration 87%Wconcentration 87%Wconcentration 74%ESEconcentration 35%ESEconcentration 97%ESEconcentration 99%ESEconcentration 83%SEconcentration 64%SWconcentration 90%SWconcentration 99%SEconcentration 69%SSEconcentration 81%Sconcentration 85%SWconcentration 99%SWconcentration 92%Wconcentration 91%
Mean water temperature(°C)10.810.810.810.810.810.810.810.810.810.910.810.810.810.810.910.810.910.910.910.810.810.810.810.810.810.910.911.111.311.2

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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 Regional Coastal Monitoring Programme.

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

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