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St Mary's Sound wave buoy daily means for Jul 2017

Daily means from the St Mary's Sound wave buoy for Jul 2017, 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

744 wave-buoy observations covered all 31 days. Typical wave height was 2.1 ft (10th–90th percentile 1.2–4.4 ft), while the reported wave period averaged 7.4 seconds (10th–90th percentile 5–10 seconds). Mean water temperature was 14.9°C (10th–90th percentile 14.3–15.8°C). 5 of 2,976 checked values (0.2%) were excluded by quality control. Across 1 comparable year, mean wave height was above the same-month mean of 2.2 ft and mean wave period was below the same-month mean of 7.5 seconds.

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

Typical Significant Wave Height

2.1ft
Mean: 2.5 ft
P10–P90: 1.2 — 4.4 ft
Recorded extremes

0.7 — 8.9 ft

Mean Observed Wave Period

7.4secs
P10–P90: 5 — 10secs
Recorded extremes

3 — 15secs

Available for 739 of 744 hourly samples

Observed Wave Direction

W

Circular concentration: 52%

Mean Water Temperature

14.9°C
P10–P90: 14.3 — 15.8°C
Recorded extremes

14.1 — 16.9°C

Compared With Previous Julys

Historical baseline from 687 observations across 1 year.

Wave Height
2.5ft
0.3ft above mean
Historical mean 2.2ft
Wave Period
7.4s
0.1s below mean
Historical mean 7.5s
Water Temperature
14.9°C
0.1°C above mean
Historical mean 14.8°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 2017Last observation shown
Metric
Mean significant wave height (ft)2221211112332222243464322335434
Mean maximum wave height (ft)-------------------------------
Mean peak period (s)-------------------------------
Mean zero-crossing period (s)-------------------------------
Mean energy period (s)-------------------------------
Mean reported period (s)79875108888679668976978767697777
Mean wave power, kilowatts per metre-------------------------------
Mean peak wave direction-------------------------------
Mean directional spread (°)-------------------------------
Mean reported wave directionNWconcentration 51%WNWconcentration 84%NWconcentration 80%NWconcentration 91%Econcentration 36%SSEconcentration 54%WNWconcentration 63%NWconcentration 92%WNWconcentration 69%WNWconcentration 81%SWconcentration 75%SWconcentration 73%WNWconcentration 60%WNWconcentration 93%WNWconcentration 92%NWconcentration 91%NNWconcentration 71%Econcentration 56%SEconcentration 47%Wconcentration 72%SWconcentration 92%SWconcentration 84%WSWconcentration 68%WSWconcentration 80%Wconcentration 78%WSWconcentration 78%WNWconcentration 76%SWconcentration 89%SWconcentration 79%SSWconcentration 92%SWconcentration 93%
Mean water temperature(°C)14.214.514.514.815.715.514.915.114.714.814.514.915.115.115.014.815.415.915.115.114.714.614.814.914.714.314.414.514.714.614.7

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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