Page History
...
Waves and wave meteograms
Wave meteograms (Wavegrams)
The ECWAM runs as an ensemble and produces a wide range of output in a similar manner to the ensemble atmospheric model. The forecast data are based on the current resolution the ensemble. All ensemble members use the unperturbed wave analysis as the initial condition.
Fig8.1.5-1: To view Wave Meteograms:
...
Wavegrams are also available by clicking on "clickable" ecCharts at the desired location.
Fig8.1.5-2: Alternative way to view Wave Meteograms (if desired location is known):
...
- During the forecast period, NEMO and the atmospheric ensemble alter the location and amount of sea ice allowing or hindering wave propagation. Wave forecasts may differ between models.
- Small islands may be unrepresented by a land grid point and ECWAM wave energy will pass the location undisturbed, rather than being partly blocked by the island as it ought to be.
- Constructive interference of waves can occur giving much higher energy or wave heights but is not evaluated by ECWAM.
- Much larger waves than shown by the model can occur locally in coastal waters with a shelving sea bed, or where there is a contrary sea current.
Fig8.1.5-3: An example of a ECWAM ensemble wave Meteogram for the southern Denmark Strait (near 64N 35W) DT 00UTC 11 May 2017. A strengthening NE wind is forecast over the location giving rise to amplified waves with increasing periods. The mean wave direction indicates that on Saturday 13 May the waves become more directed towards the SSW with a higher proportion of ECWAM ensemble members showing very large waves (exceeding 9m significant wave height). Note wind directions indicate where the wind blows from; wave directions indicate the direction the waves travel towards. The dotted red and continuous blue lines are the values of the ensemble control WAM and HRES WAM forecasts respectively.
...
The significant wave height corresponds to the average wave height of the one third highest waves (H1/3). This means that there will be some waves of greater trough-to-crest height than indicated by the significant wave height. Interference of wave trains, a shelving sea bed, or a contrary sea current are not represented in ECWAM and so may also induce much larger waves than shown. The mean wave direction is the spectrally averaged propagation direction of the waves (weighted by amplitude).
Example Wave Charts
Fig8.1.5-4: An example of Significant wave height / Mean wave direction and height on ecCharts. DT Thursday 11 May, 00 UTC T+60, VT Saturday 13 May, 12 UTC. Note: Dark blue generally indicates areas in open water where waves are forecast to be very small (e.g. among the islands off western Scotland), but the area of dark blue off the Greenland coast is in effect denoting sea ice. The ice extent is modified during the forecast by information passed from NEMO to ECWAM. This may affect the development of synoptic scale developments in the atmosphere with consequent influence over the forecast winds.
Significant wave height / Mean wave direction and height is also available on web free access charts.
Fig8.1.5-5: An example of Significant wave height probability greater than 4m. DT Thursday 11 May, 00 UTC T+60, VT Saturday 13 May, 12 UTC.
Significant wave height probability is also available on web free access charts.
Fig8.1.5-6: An example of wave energy flux magnitude (KW/m). DT Thursday 11 May, 00 UTC T+60, VT Saturday 13 May, 12UTC. Colour thresholds are at 40KW/m intervals - lightest pink represents <40KW/m.
The energy carried by swell and wind waves is important to aid assessment of potential damage to shorelines or fixed marine installations (e.g. oil rigs) and also as a guide to potential output of marine wave energy generation installations. Charts of wave energy flux magnitude (the integral over all frequencies and directions of the product of the group speed and the two-dimensional energy wave spectrum) are available on ecCharts.
Long Swell Forecasts
Fig8.1.5-7: Long swell forecasts. ECWAM DT 00UTC 4 Jan 2014. In the mid-Atlantic, significant wave height (left) is very high at about 20m. This consists of swell at several periods. Also shown is the wave energy in terms of swell height for:
...
Note the wavelengths differ but are about 1km. Wind waves have much shorter wavelengths.
Additional Sources of Information
(Note: In older material there may be references to issues that have subsequently been addressed)
...
Overview
Community Forums
Content Tools