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Greenwich wave buoy monthly means for 2021

Monthly means from the Greenwich wave buoy for 2021, including available wave height, period, direction, wind and sea temperature data.

Last observation shown

Data available:  to 

Latest

Period Summary

Programmatically generated summary. Hog Says

5,877 wave-buoy observations covered 290 of 365 days (79%). Typical wave height was 1.6 ft (10th–90th percentile 0.7–5.6 ft), while mean reported wave period; measurement type unavailable was 6.6 seconds (10th–90th percentile 5–9 seconds). Typical wind was 18.3 mph (10th–90th percentile 8.1–31.1 mph) and mean water temperature was 13°C (10th–90th percentile 8.8–17.2°C). 42 of 29,385 checked values (0.1%) were excluded by quality control.

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

Typical Wave Height

1.6ft
Mean: 2.5 ft
P10–P90: 0.7 — 5.6 ft
Recorded extremes

0 — 15.4 ft

Available for 5,867 of 5,877 hourly samples

Mean Wave Period

6.6secs
P10–P90: 5 — 9secs
Recorded extremes

2 — 26secs

Available for 5,858 of 5,877 hourly samples

Mean Water Temperature

13°C
P10–P90: 8.8 — 17.2°C
Recorded extremes

7.8 — 19.5°C

Available for 5,869 of 5,877 hourly samples

Typical Wind

Variable, 18.3mph
Mean: 19.1 mph
P10–P90: 8.1 — 31.1 mph
Recorded extremes

0 — 49.4 mph

Circular concentration: 19%

Available for 5,872 of 5,877 hourly samples

Chart showing grouped wave observations for Greenwich. Use the table on this page for a text version of the same measurements. To open daily observations, use a linked month 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; months run left to right.
Greenwich wave buoy monthly means 2021Last observation shown
Metric
Mean wave height (ft)432231122334
Mean observed period(s)7Reported7Reported7Reported5Reported6Reported6Reported5Reported7Reported8Reported7Reported7Reported7Reported
Mean wave power(kW/m)------------
Mean wind directionWNWconcentration 65%Variableconcentration 8%Variableconcentration 24%NNEconcentration 49%SWconcentration 48%Variableconcentration 25%SWconcentration 62%Wconcentration 35%Variableconcentration 5%SWconcentration 48%NWconcentration 52%SWconcentration 37%
Mean wind speed (mph)21231818201171716212023
Mean water temperature(°C)9.49.08.89.010.513.617.116.717.416.214.111.6

Swipe sideways to see more months.

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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