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Chesil wave buoy daily means for Apr 2021

Daily means from the Chesil 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

1,440 wave-buoy observations covered all 30 days. Typical wave height was 1.1 ft (10th–90th percentile 0.6–2.3 ft), while mean average of more than one wave period type was 8.2 seconds (10th–90th percentile 3.5–12.6 seconds). Mean water temperature was 9.7°C (10th–90th percentile 9.2–10.4°C). 30 of 5,674 checked values (0.5%) were excluded by quality control. Across 11 comparable years, mean wave height was below the same-month mean of 2.5 ft and mean wave period was below the same-month mean of 8.9 seconds.

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

Typical Significant Wave Height

1.1ft
Mean: 1.3 ft
P10–P90: 0.6 — 2.3 ft
Recorded extremes

0.4 — 4.2 ft

Mean Observed Wave Period

8.2secs
P10–P90: 3.5 — 12.6secs
Recorded extremes

2.1 — 20secs

Available for 716 of 720 hourly samples

Observed Wave Direction

SSW

Circular concentration: 79%

Mean Water Temperature

9.7°C
P10–P90: 9.2 — 10.4°C
Recorded extremes

7.1 — 11.2°C

Compared With Previous Aprils

Historical baseline from 15,778 observations across 11 years.

Wave Height
1.3ft
1.2ft below mean
Historical mean 2.461ft
Wave Period
8.2s
0.7s below mean
Historical mean 8.9s
Water Temperature
9.7°C
0.1°C below mean
Historical mean 9.8°C

Chart showing grouped wave observations for Chesil. 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 Chesil wave buoy

Chesil is a Channel Coastal Observatory National Network wave station off Dorset's exposed Jurassic Coast. It records waves approaching Chesil Beach and the western side of Portland, providing a nearshore reference for the long shingle barrier and the communities and infrastructure behind it.

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.
Chesil wave buoy daily means Apr 2021Last observation shown
Metric
Mean significant wave height (ft)222121121112111111111223321111
Mean maximum wave height (ft)232222122123111212222334542121
Mean peak period (s)117656576796471311111011101010771212866511
Mean zero-crossing period (s)765433333543444544565445654444
Mean energy period (s)------------------------------
Mean wave power, kilowatts per metre------------------------------
Mean peak wave directionSWconcentration 91%Sconcentration 97%SSEconcentration 99%Sconcentration 85%WSWconcentration 83%Wconcentration 77%SWconcentration 74%SWconcentration 90%SWconcentration 71%SSWconcentration 75%Sconcentration 90%SWconcentration 95%SSWconcentration 91%SSWconcentration 65%SSWconcentration 74%SSWconcentration 79%SWconcentration 88%SSWconcentration 88%SWconcentration 97%SWconcentration 99%SWconcentration 91%SSEconcentration 95%SSEconcentration 91%SSWconcentration 87%SSWconcentration 92%Sconcentration 94%Sconcentration 91%Sconcentration 83%SSWconcentration 81%SSWconcentration 74%
Mean directional spread (°)41.827.631.133.436.826.746.949.943.458.035.730.446.365.456.856.260.655.654.449.851.531.931.141.135.829.736.649.733.260.6
Mean water temperature(°C)9.49.49.49.49.39.19.19.09.39.39.39.39.49.59.49.59.69.89.910.110.110.010.010.210.210.410.610.610.410.5

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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