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

Daily means from the St Mary's Sound wave buoy for Mar 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 4.9 ft (10th–90th percentile 2.9–8.1 ft), while mean average of more than one wave period type was 9.2 seconds (10th–90th percentile 5.8–13.3 seconds). Mean water temperature was 9.8°C (10th–90th percentile 9.8–9.9°C). 22 of 5,896 checked values (0.4%) were excluded by quality control. Across 3 comparable years, mean wave height was above the same-month mean of 5.2 ft and mean wave period was below the same-month mean of 9.6 seconds.

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

Typical Significant Wave Height

4.9ft
Mean: 5.3 ft
P10–P90: 2.9 — 8.1 ft
Recorded extremes

1.8 — 14.6 ft

Mean Observed Wave Period

9.2secs
P10–P90: 5.8 — 13.3secs
Recorded extremes

3.7 — 18.2secs

Available for 740 of 743 hourly samples

Observed Wave Direction

Variable

Circular concentration: 19%

Most common: SW (25%) · circular mean SSW

Mean Water Temperature

9.8°C
P10–P90: 9.8 — 9.9°C
Recorded extremes

9.7 — 10.1°C

Compared With Previous Marchs

Historical baseline from 2,229 observations across 3 years.

Wave Height
5.3ft
0.1ft above mean
Historical mean 5.184ft
Wave Period
9.2s
0.4s below mean
Historical mean 9.6s
Water Temperature
9.8°C
0.2°C below mean
Historical mean 10°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 Mar 2020Last observation shown
Metric
Mean significant wave height (ft)76454468676655534438QC rejected6433334866
Mean maximum wave height (ft)109786791210101098885665132096444571299
Mean peak period (s)1010119911101011981010881181113898714121066987
Mean zero-crossing period (s)6665555666665566454565555554655
Mean energy period (s)-------------------------------
Mean reported period (s)1010119911111012991010981281113798714121176887
Mean wave power, kilowatts per metre-------------------------------
Mean peak wave directionSWconcentration 96%SWconcentration 84%WSWconcentration 63%SSWconcentration 100%SWconcentration 67%WSWconcentration 75%Wconcentration 66%SWconcentration 95%Wconcentration 66%SWconcentration 77%SWconcentration 86%WSWconcentration 61%WSWconcentration 45%SWconcentration 79%SWconcentration 75%WNWconcentration 69%Wconcentration 59%NWconcentration 48%NNEconcentration 71%Econcentration 100%ESEconcentration 100%ESEconcentration 99%ESEconcentration 99%Nconcentration 74%NWconcentration 38%Variableconcentration 15%Econcentration 84%Econcentration 99%Econcentration 100%Econcentration 100%Econcentration 100%
Mean directional spread (°)38.836.045.132.040.241.444.435.941.536.535.239.543.039.636.754.936.741.851.721.717.222.025.447.747.245.932.827.819.621.222.7
Mean reported wave directionSWconcentration 88%SWconcentration 79%WSWconcentration 62%SSWconcentration 100%SWconcentration 65%WSWconcentration 79%WSWconcentration 62%SWconcentration 82%Wconcentration 60%SWconcentration 72%SWconcentration 69%Wconcentration 56%WSWconcentration 47%SWconcentration 71%SWconcentration 74%WNWconcentration 65%WSWconcentration 60%WNWconcentration 47%NNEconcentration 60%Econcentration 99%ESEconcentration 100%ESEconcentration 99%ESEconcentration 99%Nconcentration 56%NWconcentration 35%Variableconcentration 9%ESEconcentration 78%Econcentration 99%Econcentration 100%Econcentration 100%Econcentration 100%
Mean water temperature(°C)9.89.89.89.89.89.79.89.89.89.89.89.89.89.89.89.89.89.99.89.89.89.89.89.99.99.99.99.99.99.89.8

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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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