Skip to content
Surfhog home
Menu

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

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

1,485 wave-buoy observations covered all 31 days. Typical wave height was 5.6 ft (10th–90th percentile 2.7–9.6 ft), while mean average of more than one wave period type was 9.2 seconds (10th–90th percentile 5.5–12.6 seconds). Mean water temperature was 10.6°C (10th–90th percentile 10.3–10.8°C). 15 of 5,884 checked values (0.3%) were excluded by quality control. Across 3 comparable years, mean wave height was above the same-month mean of 4.7 ft and mean wave period was the same as the same-month mean of 9.2 seconds.

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

Typical Significant Wave Height

5.6ft
Mean: 5.9 ft
P10–P90: 2.7 — 9.6 ft
Recorded extremes

1.9 — 15.7 ft

Mean Observed Wave Period

9.2secs
P10–P90: 5.5 — 12.6secs
Recorded extremes

3.7 — 18.2secs

Available for 741 of 743 hourly samples

Observed Wave Direction

SW

Circular concentration: 64%

Mean Water Temperature

10.6°C
P10–P90: 10.3 — 10.8°C
Recorded extremes

10 — 10.9°C

Compared With Previous Januarys

Historical baseline from 2,146 observations across 3 years.

Wave Height
5.9ft
1.2ft above mean
Historical mean 4.724ft
Wave Period
9.2s
In line with the historical mean
Historical mean 9.2s
Water Temperature
10.6°C
0.3°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 Jan 2020Last observation shown
Metric
Mean significant wave height (ft)36534866768710131112854233533577567
Mean maximum wave height (ft)510855121091191310151917181286445844811117911
Mean peak period (s)10711118781191181010111291110913151076768101178
Mean zero-crossing period (s)5566465666666777655555544566556
Mean energy period (s)-------------------------------
Mean reported period (s)7710108781191181010111210111091315977768101278
Mean wave power, kilowatts per metre-------------------------------
Mean peak wave directionSWconcentration 98%SWconcentration 98%WSWconcentration 75%WSWconcentration 85%SWconcentration 94%SSWconcentration 99%SWconcentration 93%WSWconcentration 53%SWconcentration 85%WSWconcentration 68%SWconcentration 92%SWconcentration 73%SWconcentration 71%SSWconcentration 99%SSWconcentration 100%SSWconcentration 99%SWconcentration 97%SSWconcentration 89%SSWconcentration 63%WNWconcentration 64%NNWconcentration 70%Variableconcentration 11%ESEconcentration 99%ESEconcentration 85%SEconcentration 56%SSWconcentration 98%SSWconcentration 100%WSWconcentration 77%Wconcentration 52%Sconcentration 98%SSWconcentration 100%
Mean directional spread (°)43.430.939.948.041.529.534.141.333.043.932.234.534.028.326.827.229.134.736.053.958.446.524.131.536.132.233.843.551.030.830.1
Mean reported wave directionWSWconcentration 67%SWconcentration 99%WSWconcentration 76%WSWconcentration 78%SWconcentration 91%SSWconcentration 99%SWconcentration 85%WSWconcentration 52%SWconcentration 75%WSWconcentration 63%SWconcentration 84%SWconcentration 74%SWconcentration 79%SSWconcentration 99%SSWconcentration 100%SSWconcentration 99%SSWconcentration 96%SSWconcentration 93%SSWconcentration 59%WNWconcentration 52%NNWconcentration 82%Variableconcentration 19%ESEconcentration 99%ESEconcentration 84%SEconcentration 48%SSWconcentration 98%SSWconcentration 93%WSWconcentration 79%Wconcentration 42%SSWconcentration 91%SSWconcentration 100%
Mean water temperature(°C)10.910.910.910.810.810.810.810.810.810.810.810.810.810.810.710.710.710.610.610.510.510.410.410.410.410.410.410.310.310.310.3

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.

› Wave Buoy List