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

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

736 wave-buoy observations covered all 31 days. Typical wave height was 1.3 ft (10th–90th percentile 0.9–4.3 ft), while the reported wave period averaged 9.2 seconds (10th–90th percentile 5–14 seconds). Mean water temperature was 16.1°C (10th–90th percentile 14.7–17.9°C). 23 of 2,944 checked values (0.8%) were excluded by quality control. Across 2 comparable years, mean wave height was below the same-month mean of 2.4 ft and mean wave period was above the same-month mean of 7.4 seconds.

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

Typical Significant Wave Height

1.3ft
Mean: 2 ft
P10–P90: 0.9 — 4.3 ft
Recorded extremes

0.8 — 11.8 ft

Mean Observed Wave Period

9.2secs
P10–P90: 5 — 14secs
Recorded extremes

3 — 20secs

Available for 714 of 736 hourly samples

Observed Wave Direction

WSW

Circular concentration: 36%

Mean Water Temperature

16.1°C
P10–P90: 14.7 — 17.9°C
Recorded extremes

13.5 — 20.9°C

Available for 735 of 736 hourly samples

Compared With Previous Julys

Historical baseline from 1,431 observations across 2 years.

Wave Height
2ft
0.4ft below mean
Historical mean 2.4ft
Wave Period
9.2s
1.8s above mean
Historical mean 7.4s
Water Temperature
16.1°C
1.2°C above mean
Historical mean 14.9°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 Jul 2018Last observation shown
Metric
Mean significant wave height (ft)2222111112111112221111111246954
Mean maximum wave height (ft)-------------------------------
Mean peak period (s)-------------------------------
Mean zero-crossing period (s)-------------------------------
Mean energy period (s)-------------------------------
Mean reported period (s)796412139101171112171615121198767569768988
Mean wave power, kilowatts per metre-------------------------------
Mean peak wave direction-------------------------------
Mean directional spread (°)-------------------------------
Mean reported wave directionEconcentration 54%NNWconcentration 50%Econcentration 85%ESEconcentration 80%SWconcentration 58%SWconcentration 62%SWconcentration 89%Wconcentration 49%NNWconcentration 86%NEconcentration 58%NNWconcentration 82%Variableconcentration 18%SSWconcentration 86%SSWconcentration 98%SSWconcentration 98%NWconcentration 59%NWconcentration 58%WNWconcentration 63%Wconcentration 69%Wconcentration 81%WNWconcentration 76%WSWconcentration 77%SWconcentration 95%WSWconcentration 80%NNWconcentration 69%WNWconcentration 57%SWconcentration 88%SWconcentration 96%SSWconcentration 99%SWconcentration 97%WSWconcentration 64%
Mean water temperature(°C)15.315.515.215.615.215.916.117.317.417.216.416.716.817.817.216.115.515.815.616.116.816.816.416.616.716.115.114.715.115.915.6

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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