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

Daily means from the St Mary's Sound wave buoy for Aug 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

1,462 wave-buoy observations covered all 31 days. Typical wave height was 2.4 ft (10th–90th percentile 1.3–5.2 ft), while mean average of more than one wave period type was 8.1 seconds (10th–90th percentile 5.3–11.5 seconds). Mean water temperature was 15.7°C (10th–90th percentile 15.2–16.5°C). 26 of 5,846 checked values (0.4%) were excluded by quality control. Across 7 comparable years, mean wave height was above the same-month mean of 2.6 ft and mean wave period was above the same-month mean of 6.5 seconds.

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

Typical Significant Wave Height

2.4ft
Mean: 3 ft
P10–P90: 1.3 — 5.2 ft
Recorded extremes

0.1 — 14.1 ft

Mean Observed Wave Period

8.1secs
P10–P90: 5.3 — 11.5secs
Recorded extremes

2.6 — 20secs

Available for 732 of 734 hourly samples

Observed Wave Direction

WSW

Circular concentration: 59%

Mean Water Temperature

15.7°C
P10–P90: 15.2 — 16.5°C
Recorded extremes

14.8 — 19.2°C

Compared With Previous Augusts

Historical baseline from 4,874 observations across 7 years.

Wave Height
3ft
0.4ft above mean
Historical mean 2.6ft
Wave Period
8.1s
1.6s above mean
Historical mean 6.5s
Water Temperature
15.7°C
In line with the historical mean
Historical mean 15.7°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 Aug 2023Last observation shown
Metric
Mean significant wave height (ft)4743532323454421168432111222222
Mean maximum wave height (ft)6116484343567663221013643222333234
Mean peak period (s)7109887765579971017178109987106667875
Mean zero-crossing period (s)5655554444555556457555444444454
Mean energy period (s)-------------------------------
Mean reported period (s)5655554444555556457555444445454
Mean wave power, kilowatts per metre-------------------------------
Mean peak wave directionSWconcentration 95%WSWconcentration 87%WNWconcentration 48%NNWconcentration 38%Wconcentration 54%Variableconcentration 29%WSWconcentration 80%WSWconcentration 76%WSWconcentration 63%SSEconcentration 88%SWconcentration 99%Wconcentration 72%WNWconcentration 65%SWconcentration 99%SSWconcentration 89%SSWconcentration 98%SSWconcentration 95%SSEconcentration 74%SSWconcentration 99%SWconcentration 98%WNWconcentration 82%WNWconcentration 86%Wconcentration 86%SWconcentration 65%WNWconcentration 87%WNWconcentration 96%NWconcentration 95%NWconcentration 91%Wconcentration 75%WNWconcentration 65%SWconcentration 79%
Mean directional spread (°)42.343.952.351.947.459.656.638.347.433.730.546.341.940.339.639.343.838.025.042.653.955.359.445.343.351.545.148.451.749.841.8
Mean reported wave directionSWconcentration 95%WSWconcentration 87%WNWconcentration 50%NNWconcentration 39%Wconcentration 54%Variableconcentration 30%WSWconcentration 81%WSWconcentration 76%WSWconcentration 66%Sconcentration 89%SWconcentration 99%Wconcentration 82%WNWconcentration 70%SWconcentration 99%SSWconcentration 80%SSWconcentration 61%SSWconcentration 95%SSEconcentration 74%SSWconcentration 99%SWconcentration 98%WNWconcentration 82%WNWconcentration 87%Wconcentration 85%WSWconcentration 67%WNWconcentration 89%NWconcentration 95%NWconcentration 95%NWconcentration 91%WNWconcentration 72%WNWconcentration 69%SWconcentration 79%
Mean water temperature(°C)15.915.415.715.615.115.215.315.015.315.215.315.716.116.016.516.016.015.415.315.715.615.815.816.316.316.216.416.715.815.815.4

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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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