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Greenwich wave buoy daily means for Dec 2020

Daily means from the Greenwich wave buoy for Dec 2020, 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

9 wave-buoy observations covered 9 of 31 days (29%). Typical wave height was 3.3 ft (10th–90th percentile 1.5–6 ft), while mean reported wave period; measurement type unavailable was 6.2 seconds (10th–90th percentile 5–7.2 seconds). Typical wind was 20.8 mph (10th–90th percentile 0–25.8 mph) and mean water temperature was 11.9°C (10th–90th percentile 11.1–12.3°C). All 45 checked values passed quality control. Across 10 comparable years, mean wave height was below the same-month mean of 4.2 ft and mean wave period was below the same-month mean of 6.6 seconds.

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

Typical Wave Height

3.3ft
Mean: 3.7 ft
P10–P90: 1.5 — 6 ft
Recorded extremes

1.3 — 6.6 ft

Mean Wave Period

6.2secs
P10–P90: 5 — 7.2secs
Recorded extremes

5 — 8secs

Mean Water Temperature

11.9°C
P10–P90: 11.1 — 12.3°C
Recorded extremes

10.9 — 12.9°C

Typical Wind

NW, 20.8mph
Mean: 15 mph
P10–P90: 0 — 25.8 mph
Recorded extremes

0 — 32.2 mph

Circular concentration: 42%

Compared With Previous Decembers

Historical baseline from 7,358 observations across 10 years.

Wave Height
3.7ft
0.5ft below mean
Historical mean 4.2ft
Wave Period
6.2s
0.4s below mean
Historical mean 6.6s
Water Temperature
11.9°C
0.1°C above mean
Historical mean 11.8°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 Dec 2020Last observation shown
Metric
Mean wave height (ft)3---6--1-------35----7--2--53--
Mean observed period(s)5Reported---6Reported--6Reported-------6Reported7Reported----7Reported--5Reported--6Reported8Reported--
Mean wave power(kW/m)-------------------------------
Mean wind directionNNWconcentration 100%---ESEconcentration 100%--Wconcentration 100%-------Nconcentration 100%SWconcentration 100%----Nconcentration 100%--NNWconcentration 100%--SWconcentration 100%Nconcentration 100%--
Mean wind speed (mph)24---32--11--------22-------21--24---
Mean water temperature(°C)12.9---12.2--12.0-------12.212.2----12.2--11.2--11.110.9--

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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