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

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

1,486 wave-buoy observations covered all 31 days. Typical wave height was 3.2 ft (10th–90th percentile 1.6–6 ft), while mean average of more than one wave period type was 7 seconds (10th–90th percentile 5.3–9.1 seconds). Mean water temperature was 15.7°C (10th–90th percentile 15.1–16.3°C). 6 of 5,942 checked values (0.1%) were excluded by quality control. Across 7 comparable years, mean wave height was above the same-month mean of 2.3 ft and mean wave period was above the same-month mean of 6.8 seconds.

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

Typical Significant Wave Height

3.2ft
Mean: 3.6 ft
P10–P90: 1.6 — 6 ft
Recorded extremes

0.8 — 11.7 ft

Mean Observed Wave Period

7secs
P10–P90: 5.3 — 9.1secs
Recorded extremes

2.8 — 12.5secs

Observed Wave Direction

WSW

Circular concentration: 72%

Mean Water Temperature

15.7°C
P10–P90: 15.1 — 16.3°C
Recorded extremes

14.4 — 17.2°C

Compared With Previous Julys

Historical baseline from 5,128 observations across 7 years.

Wave Height
3.6ft
1.3ft above mean
Historical mean 2.3ft
Wave Period
7s
0.2s above mean
Historical mean 6.8s
Water Temperature
15.7°C
0.5°C above mean
Historical mean 15.2°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 Jul 2023Last observation shown
Metric
Mean significant wave height (ft)33322447565338QC rejected4332114432343354
Mean maximum wave height (ft)5443466117975413136443227642575577
Mean peak period (s)91077766987876798766656777776677
Mean zero-crossing period (s)5554544655554665544444555454555
Mean energy period (s)-------------------------------
Mean reported period (s)5544444655554565544444555454555
Mean wave power, kilowatts per metre-------------------------------
Mean peak wave directionNWconcentration 93%NWconcentration 82%WNWconcentration 87%Wconcentration 71%WNWconcentration 77%SWconcentration 82%SSWconcentration 80%SSWconcentration 100%SWconcentration 100%SWconcentration 99%SWconcentration 98%WSWconcentration 96%Wconcentration 80%SSWconcentration 99%SWconcentration 100%SWconcentration 98%WSWconcentration 92%WSWconcentration 80%WSWconcentration 86%WSWconcentration 74%NWconcentration 44%WSWconcentration 88%SWconcentration 97%NWconcentration 47%WNWconcentration 62%WSWconcentration 81%SWconcentration 97%SWconcentration 99%SWconcentration 96%WSWconcentration 90%SWconcentration 99%
Mean directional spread (°)48.553.848.457.151.842.736.026.732.030.033.841.645.227.326.046.549.541.249.558.451.639.343.352.061.343.137.436.443.840.040.2
Mean reported wave directionNWconcentration 92%NWconcentration 78%WNWconcentration 87%Wconcentration 68%WNWconcentration 70%SWconcentration 82%SSWconcentration 80%SSWconcentration 99%SWconcentration 100%SWconcentration 99%SWconcentration 98%WSWconcentration 96%Wconcentration 80%SSWconcentration 99%SWconcentration 100%SWconcentration 98%WSWconcentration 92%WSWconcentration 80%WSWconcentration 86%WSWconcentration 71%NWconcentration 44%WSWconcentration 87%SWconcentration 97%NWconcentration 42%WNWconcentration 65%WSWconcentration 82%SWconcentration 94%SWconcentration 97%SWconcentration 96%WSWconcentration 90%SWconcentration 99%
Mean water temperature(°C)16.016.015.615.515.215.215.015.215.215.215.215.715.915.715.315.615.815.515.515.715.815.316.016.116.015.715.916.116.016.316.3

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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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