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Greenwich wave buoy daily means for Apr 2017

Daily means from the Greenwich 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

718 wave-buoy observations covered all 30 days. Typical wave height was 1 ft (10th–90th percentile 0.3–2.3 ft), while mean reported wave period; measurement type unavailable was 6.6 seconds (10th–90th percentile 4–9 seconds). Typical wind was 15 mph (10th–90th percentile 6.9–24.2 mph) and mean water temperature was 10.8°C (10th–90th percentile 10.3–11.3°C). 21 of 3,590 checked values (0.6%) were excluded by quality control. Across 6 comparable years, mean wave height was below the same-month mean of 2.3 ft and mean wave period was above the same-month mean of 6.5 seconds.

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

Typical Wave Height

1ft
Mean: 1.2 ft
P10–P90: 0.3 — 2.3 ft
Recorded extremes

0 — 4.3 ft

Available for 717 of 718 hourly samples

Mean Wave Period

6.6secs
P10–P90: 4 — 9secs
Recorded extremes

4 — 26secs

Available for 698 of 718 hourly samples

Mean Water Temperature

10.8°C
P10–P90: 10.3 — 11.3°C
Recorded extremes

9.9 — 12°C

Typical Wind

Variable, 15mph
Mean: 14.9 mph
P10–P90: 6.9 — 24.2 mph
Recorded extremes

0 — 31.1 mph

Circular concentration: 22%

Compared With Previous Aprils

Historical baseline from 4,291 observations across 6 years.

Wave Height
1.2ft
1.1ft below mean
Historical mean 2.3ft
Wave Period
6.6s
0.1s above mean
Historical mean 6.5s
Water Temperature
10.8°C
1.3°C above mean
Historical mean 9.5°C

Chart showing grouped wave observations for Greenwich. 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 Greenwich wave buoy

Greenwich Lightship (WMO 62305) is a UK Met Office station in the southern North Sea on the Greenwich meridian. It monitors marine conditions between the Dover Strait and the Thames approaches. The station feed can include wind, wave height, pressure, visibility, and air and sea temperature.

Metrics are rows; days run left to right.
Greenwich wave buoy daily means Apr 2017Last observation shown
Metric
Mean wave height (ft)321221111112111111210011121102
Mean observed period(s)7Reported9Reported8Reported10Reported9Reported8Reported7Reported8Reported7Reported6Reported6Reported5Reported5Reported5Reported5Reported5Reported5Reported5Reported5Reported9ReportedQC rejected10Reported5Reported4Reported5Reported5Reported5Reported4Reported4Reported5Reported
Mean wave power(kW/m)------------------------------
Mean wind directionSSWconcentration 98%WSWconcentration 51%SSWconcentration 85%WSWconcentration 77%NNWconcentration 73%Econcentration 43%WSWconcentration 30%Econcentration 97%SSEconcentration 52%NWconcentration 82%NWconcentration 72%Wconcentration 98%Wconcentration 75%WNWconcentration 92%Wconcentration 98%WNWconcentration 96%NEconcentration 34%NEconcentration 86%ENEconcentration 95%Variableconcentration 23%Wconcentration 99%NNEconcentration 46%SSEconcentration 70%WSWconcentration 77%NNWconcentration 87%Nconcentration 93%NWconcentration 74%WNWconcentration 82%SEconcentration 44%ESEconcentration 85%
Mean wind speed (mph)1688111588111515152314142120151321914131217182118141625
Mean water temperature(°C)10.210.410.210.310.410.810.810.710.810.610.610.610.610.710.810.810.910.810.811.011.111.111.111.111.010.810.811.011.211.2

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.

Which wave period is shown?

The table shows the best period measurement supplied for each observation. It is not necessarily the energy period used to calculate wave power.

Tp
Peak period: the period at the strongest spectral peak.
Tavg
The provider's average wave period.
Tm02
A mean period calculated from the wave spectrum.
Tz
Mean zero-crossing period.
Reported
A legacy value whose period type was not recorded.
Mixed
A daily or monthly mean containing more than one period type.

Wave power needs a genuine energy period (Te). SurfHog does not substitute Tp, Tavg, Tm02 or Tz when Te is missing.

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.

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