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Sevenstones wave buoy daily means for Apr 2017

Daily means from the Sevenstones wave buoy for Apr 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

688 wave-buoy observations covered all 30 days. Typical wave height was 2.6 ft (10th–90th percentile 1.3–8.2 ft), while the reported wave period averaged 7.6 seconds (10th–90th percentile 6–10 seconds). Typical wind was 15 mph (10th–90th percentile 8.1–25.3 mph) and mean water temperature was 11.2°C (10th–90th percentile 10.7–11.9°C). 2 of 3,192 checked values (0.1%) were excluded by quality control. Across 7 comparable years, mean wave height was below the same-month mean of 5.5 ft and mean wave period was below the same-month mean of 8.2 seconds.

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

Typical Significant Wave Height

2.6ft
Mean: 3.6 ft
P10–P90: 1.3 — 8.2 ft
Recorded extremes

1 — 12.1 ft

Available for 686 of 688 hourly samples

Mean Observed Wave Period

7.6secs
P10–P90: 6 — 10secs
Recorded extremes

5 — 12secs

Typical Observed Wind

N, 15mph
Mean: 16.1 mph
P10–P90: 8.1 — 25.3 mph
Recorded extremes

2.2 — 38 mph

Circular concentration: 39%

Mean Water Temperature

11.2°C
P10–P90: 10.7 — 11.9°C
Recorded extremes

10.6 — 12.9°C

Available for 440 of 688 hourly samples

Compared With Previous Aprils

Historical baseline from 5,011 observations across 7 years.

Wave Height
3.6ft
1.9ft below mean
Historical mean 5.5ft
Wave Period
7.6s
0.6s below mean
Historical mean 8.2s
Water Temperature
11.2°C
1°C above mean
Historical mean 10.2°C

Chart showing grouped wave observations for Sevenstones. 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 Sevenstones wave buoy

Sevenstones Lightship (WMO 62107) is a UK Met Office station west of Land's End, near the Seven Stones reef in the Western Approaches. Its exposed offshore position shows Atlantic systems before they reach Cornwall and the western English Channel and provides context for a notoriously hazardous shipping area.

Its current data source reports wave height, wave period, wave direction, directional spread, wind conditions, sea temperature, separate swell and wind-sea components and wave spectra.

Metrics are rows; days run left to right.
Sevenstones wave buoy daily means Apr 2017Last observation shown
Metric
Mean significant wave height (ft)8661084333433322322122221QC rejected42249
Mean maximum wave height (ft)------------------------------
Mean maximum crest height (ft)------------------------------
Mean maximum trough height (ft)------------------------------
Mean peak period (s)------------------------------
Mean average period (s)------------------------------
Mean period Tm02 (s)------------------------------
Mean zero-crossing period (s)------------------------------
Mean maximum wave period (s)------------------------------
Mean reported period (s)9881010910109876776766679978665589
Mean peak wave direction------------------------------
Mean wave direction------------------------------
Mean directional spread (°)------------------------------
Mean wind directionWNWconcentration 86%WNWconcentration 44%SSWconcentration 91%NNWconcentration 92%Nconcentration 99%NEconcentration 87%NEconcentration 96%ESEconcentration 91%Wconcentration 64%NNWconcentration 88%Nconcentration 90%WNWconcentration 95%NWconcentration 88%Wconcentration 96%NWconcentration 87%WNWconcentration 92%Nconcentration 91%ENEconcentration 61%Econcentration 94%ENEconcentration 42%NNEconcentration 89%NNEconcentration 97%Econcentration 62%NWconcentration 62%Nconcentration 96%NNEconcentration 92%NNWconcentration 88%WNWconcentration 61%SSEconcentration 91%WSWconcentration 52%
Mean wind speed (mph)2111232518151116131914181113151717159813161210272115112326
Mean water temperature(°C)-----------10.710.710.810.810.810.910.911.211.711.911.811.711.811.110.810.911.111.111.1

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 Met Office Marine observations.

Learn how SurfHog combines, checks and summarizes observations in the data and methodology notes.

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