Skip to content
Surfhog home
Menu

Sevenstones wave buoy daily means for Apr 2021

Daily means from the Sevenstones wave buoy for Apr 2021, 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

717 wave-buoy observations covered all 30 days. Typical wave height was 3.3 ft (10th–90th percentile 1.6–4.9 ft), while the reported wave period averaged 6.8 seconds (10th–90th percentile 6–9 seconds). Typical wind was 16.1 mph (10th–90th percentile 8.1–30 mph) and mean water temperature was 10.4°C (10th–90th percentile 10.1–10.7°C). 1 of 3,585 checked values (0%) were excluded by quality control. Across 11 comparable years, mean wave height was below the same-month mean of 5.4 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

3.3ft
Mean: 3.1 ft
P10–P90: 1.6 — 4.9 ft
Recorded extremes

1 — 7.5 ft

Available for 716 of 717 hourly samples

Mean Observed Wave Period

6.8secs
P10–P90: 6 — 9secs
Recorded extremes

5 — 12secs

Typical Observed Wind

NE, 16.1mph
Mean: 17.5 mph
P10–P90: 8.1 — 30 mph
Recorded extremes

2.2 — 38 mph

Circular concentration: 48%

Mean Water Temperature

10.4°C
P10–P90: 10.1 — 10.7°C
Recorded extremes

9.9 — 11.1°C

Compared With Previous Aprils

Historical baseline from 7,847 observations across 11 years.

Wave Height
3.1ft
2.3ft below mean
Historical mean 5.4ft
Wave Period
6.8s
1.4s below mean
Historical mean 8.2s
Water Temperature
10.4°C
0.1°C above mean
Historical mean 10.3°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 2021Last observation shown
Metric
Mean significant wave height (ft)443244322332122235443545642432
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)866766666666766689998666776677
Mean peak wave direction------------------------------
Mean wave direction------------------------------
Mean directional spread (°)------------------------------
Mean wind directionENEconcentration 94%ENEconcentration 91%ENEconcentration 91%NNEconcentration 59%Nconcentration 96%Nconcentration 99%NNWconcentration 84%SSWconcentration 97%WNWconcentration 71%NNEconcentration 94%Nconcentration 96%WNWconcentration 91%Econcentration 89%Econcentration 90%Econcentration 92%ESEconcentration 91%ESEconcentration 77%SSEconcentration 96%SSEconcentration 94%ENEconcentration 65%ENEconcentration 91%Econcentration 99%Econcentration 100%Econcentration 98%Econcentration 98%NEconcentration 93%NNWconcentration 89%Nconcentration 96%NEconcentration 70%Nconcentration 96%
Mean wind speed (mph)19171610272517117242214111315111010141016323432282014231112
Mean water temperature(°C)10.210.310.210.410.210.010.110.310.410.210.110.210.310.410.310.310.410.510.510.610.710.410.310.510.610.510.610.510.610.7

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 Met Office Marine observations.

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

› Wave Buoy List