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St Mary's Sound wave buoy daily means for Aug 2020

Daily means from the St Mary's Sound wave buoy for Aug 2020, 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

1,486 wave-buoy observations covered all 31 days. Typical wave height was 2.1 ft (10th–90th percentile 1.1–6.8 ft), while mean average of more than one wave period type was 7.4 seconds (10th–90th percentile 4.9–9.8 seconds). Mean water temperature was 15.6°C (10th–90th percentile 14.8–16.5°C). 6 of 5,914 checked values (0.1%) were excluded by quality control. Across 4 comparable years, mean wave height was above the same-month mean of 2.6 ft and mean wave period was below the same-month mean of 7.6 seconds.

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

Typical Significant Wave Height

2.1ft
Mean: 3.1 ft
P10–P90: 1.1 — 6.8 ft
Recorded extremes

0.8 — 15.2 ft

Mean Observed Wave Period

7.4secs
P10–P90: 4.9 — 9.8secs
Recorded extremes

2.6 — 14.3secs

Observed Wave Direction

WSW

Circular concentration: 61%

Mean Water Temperature

15.6°C
P10–P90: 14.8 — 16.5°C
Recorded extremes

14.2 — 17.8°C

Compared With Previous Augusts

Historical baseline from 2,650 observations across 4 years.

Wave Height
3.1ft
0.5ft above mean
Historical mean 2.592ft
Wave Period
7.4s
0.2s below mean
Historical mean 7.6s
Water Temperature
15.6°C
In line with the historical mean
Historical mean 15.6°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 Aug 2020Last observation shown
Metric
Mean significant wave height (ft)322353222111111112711105328444222
Mean maximum wave height (ft)44247533222222222311161685414666433
Mean peak period (s)988667988898987655710118759978865
Mean zero-crossing period (s)5554555554444454445675546555444
Mean energy period (s)-------------------------------
Mean reported period (s)987677988898887655810118759978865
Mean wave power, kilowatts per metre-------------------------------
Mean peak wave directionWSWconcentration 90%WSWconcentration 92%WSWconcentration 81%WSWconcentration 90%SWconcentration 95%SWconcentration 80%WSWconcentration 80%Wconcentration 88%NWconcentration 60%WNWconcentration 59%NWconcentration 80%NWconcentration 95%NWconcentration 96%WNWconcentration 75%SWconcentration 91%SWconcentration 95%SSWconcentration 70%SSWconcentration 98%Sconcentration 96%SSWconcentration 98%SSWconcentration 99%SWconcentration 92%WSWconcentration 86%SWconcentration 92%SWconcentration 97%WSWconcentration 90%SWconcentration 88%WSWconcentration 85%Nconcentration 78%ENEconcentration 97%SSEconcentration 76%
Mean directional spread (°)48.750.655.441.636.243.155.355.649.150.049.957.053.153.752.644.739.437.827.126.732.746.654.844.632.753.740.443.461.647.239.3
Mean reported wave directionWSWconcentration 86%WSWconcentration 92%WSWconcentration 81%SWconcentration 91%SWconcentration 90%SWconcentration 75%WSWconcentration 73%Wconcentration 83%NWconcentration 52%WNWconcentration 55%NWconcentration 83%NWconcentration 91%NWconcentration 91%WNWconcentration 71%SWconcentration 90%SWconcentration 83%SSWconcentration 67%SSWconcentration 98%Sconcentration 95%SWconcentration 96%SWconcentration 96%SWconcentration 93%WSWconcentration 85%SSWconcentration 91%SWconcentration 97%Wconcentration 81%SWconcentration 91%WSWconcentration 80%Nconcentration 70%ENEconcentration 96%SSEconcentration 74%
Mean water temperature(°C)14.815.115.615.214.715.315.214.915.415.715.916.316.816.016.416.615.615.515.515.015.115.315.615.515.115.715.915.616.115.815.4

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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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