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

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

1,141 wave-buoy observations covered 24 of 31 days (77%). Typical wave height was 2.5 ft (10th–90th percentile 1.5–5.5 ft), while mean average of more than one wave period type was 8.2 seconds (10th–90th percentile 4.9–11.8 seconds). Mean water temperature was 11.9°C (10th–90th percentile 11.3–12.8°C). 16 of 4,536 checked values (0.4%) were excluded by quality control. Across 3 comparable years, mean wave height was above the same-month mean of 3 ft and mean wave period was below the same-month mean of 8.8 seconds.

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

Typical Significant Wave Height

2.5ft
Mean: 3.1 ft
P10–P90: 1.5 — 5.5 ft
Recorded extremes

0.6 — 9.3 ft

Available for 570 of 571 hourly samples

Mean Observed Wave Period

8.2secs
P10–P90: 4.9 — 11.8secs
Recorded extremes

3 — 15.4secs

Available for 568 of 571 hourly samples

Observed Wave Direction

Variable

Circular concentration: 10%

Most common: ESE (21%) · circular mean SSW

Mean Water Temperature

11.9°C
P10–P90: 11.3 — 12.8°C
Recorded extremes

11.1 — 14.6°C

Compared With Previous Mays

Historical baseline from 2,226 observations across 3 years.

Wave Height
3.1ft
0.1ft above mean
Historical mean 2.953ft
Wave Period
8.2s
0.6s below mean
Historical mean 8.8s
Water Temperature
11.9°C
0.2°C above mean
Historical mean 11.7°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 May 2020Last observation shown
Metric
Mean significant wave height (ft)-------22274352112223QC rejectedQC rejected32224533
Mean maximum wave height (ft)-------43311648322333511854336756
Mean peak period (s)-------771087578111099109810101012116655
Mean zero-crossing period (s)-------544554545445456565654444
Mean energy period (s)-------------------------------
Mean reported period (s)-------791187578111099109810101112127655
Mean wave power, kilowatts per metre-------------------------------
Mean peak wave direction-------Sconcentration 67%Sconcentration 61%SSWconcentration 54%Econcentration 99%ESEconcentration 100%Econcentration 98%ESEconcentration 99%Econcentration 48%Wconcentration 87%WNWconcentration 90%WNWconcentration 89%WNWconcentration 85%WNWconcentration 68%SWconcentration 58%SWconcentration 93%WSWconcentration 91%WSWconcentration 81%Wconcentration 65%NWconcentration 77%NWconcentration 72%Econcentration 64%Econcentration 99%Econcentration 99%Econcentration 99%
Mean directional spread (°)-------34.734.449.223.425.029.722.931.359.055.949.351.049.648.136.753.556.658.558.158.732.723.325.724.1
Mean reported wave direction-------Sconcentration 63%Sconcentration 72%SSWconcentration 59%Econcentration 91%ESEconcentration 100%ESEconcentration 93%ESEconcentration 99%Econcentration 56%Wconcentration 77%WNWconcentration 80%WNWconcentration 89%WNWconcentration 86%WNWconcentration 69%SWconcentration 61%SWconcentration 93%WSWconcentration 87%Wconcentration 84%WNWconcentration 66%NWconcentration 74%NNWconcentration 68%Econcentration 58%Econcentration 99%Econcentration 99%Econcentration 99%
Mean water temperature(°C)-------11.211.311.311.311.311.311.311.511.611.711.711.911.911.911.912.112.212.212.412.512.612.813.013.7

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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