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St Mary's Sound wave buoy daily means for Apr 2018

Daily means from the St Mary's Sound wave buoy for Apr 2018, 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

719 wave-buoy observations covered all 30 days. Typical wave height was 3.7 ft (10th–90th percentile 2–9.4 ft), while the reported wave period averaged 9.5 seconds (10th–90th percentile 6–13 seconds). Mean water temperature was 10°C (10th–90th percentile 9.4–10.5°C). 4 of 2,876 checked values (0.1%) were excluded by quality control. Across 1 comparable year, mean wave height was above the same-month mean of 2.3 ft and mean wave period was above the same-month mean of 8.4 seconds.

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

Typical Significant Wave Height

3.7ft
Mean: 4.9 ft
P10–P90: 2 — 9.4 ft
Recorded extremes

0.6 — 14.8 ft

Mean Observed Wave Period

9.5secs
P10–P90: 6 — 13secs
Recorded extremes

4 — 17secs

Available for 715 of 719 hourly samples

Observed Wave Direction

SW

Circular concentration: 49%

Mean Water Temperature

10°C
P10–P90: 9.4 — 10.5°C
Recorded extremes

9.2 — 11.4°C

Compared With Previous Aprils

Historical baseline from 709 observations across 1 year.

Wave Height
4.9ft
2.6ft above mean
Historical mean 2.3ft
Wave Period
9.5s
1.1s above mean
Historical mean 8.4s
Water Temperature
10°C
0.9°C below mean
Historical mean 10.9°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 2018Last observation shown
Metric
Mean significant wave height (ft)58786106434333498128532234336322
Mean maximum wave height (ft)------------------------------
Mean peak period (s)------------------------------
Mean zero-crossing period (s)------------------------------
Mean energy period (s)------------------------------
Mean reported period (s)710810910109101213101411910101010111110968118887
Mean wave power, kilowatts per metre------------------------------
Mean peak wave direction------------------------------
Mean directional spread (°)------------------------------
Mean reported wave directionSSEconcentration 67%SSWconcentration 99%SSWconcentration 99%SSWconcentration 99%SSWconcentration 92%SSWconcentration 97%SWconcentration 99%SWconcentration 97%Wconcentration 67%NWconcentration 89%WNWconcentration 44%ENEconcentration 53%NNWconcentration 77%Wconcentration 44%SSWconcentration 90%SWconcentration 73%SSWconcentration 91%SWconcentration 81%WSWconcentration 79%Wconcentration 57%NWconcentration 67%NWconcentration 77%WNWconcentration 70%SWconcentration 93%Wconcentration 60%NWconcentration 58%SSWconcentration 76%SWconcentration 63%SSEconcentration 44%Econcentration 79%
Mean water temperature(°C)9.39.39.49.49.59.59.69.79.89.810.19.99.99.99.910.010.010.210.310.310.310.310.310.410.410.510.510.510.510.5

Swipe sideways to see more days.

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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