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  1. On charts page, click ENS Meteograms.
  2. Select wave ENSgram from drop-down menu or display all ENSgrams by clicking on square icon.
  3. Select location by name or Lat/Long.


View directly the an example of the wavegram site.


The divergence between the ECWAM ensemble members with respect to ocean waves is, therefore, due only to different wind forcing.  This can be attributable only to the coupled atmospheric ensemble members evolving in different ways, and indeed starting out from T+0 with (slightly) different fields of 10m winds (and other atmospheric parameters).   The ECWAM ensemble wavegram provides a probabilistic interpretation of the ECWAM ensemble for specific locations.  It displays the time evolution of the distribution of several marine parameters from the ECWAM ensemble at each forecast range by a box and whisker plot and information on wind and wave movement by a polar diagram (See Fig8.1.6.2).

  • 10 m wind direction (““wind rose””) is divided into eight main directions or octants, each covering 45° (N, NE, E, SE etc,  i.e. the northerly octant is between 337.5° and 22.5°).  The length of the radius of an octant is proportional to the probability of that wind direction and the exact probability of each octant is indicated by shading, using a continuous colour scale from light to dark blue given by the colour scale in the upper right corner.   The probability is taken as the proportion of atmospheric ensemble member forecasts verifying that day at 00UTC, 06UTC, 12UTC and 18UTC and falling in each octant.  Note:
    • The size of the wind rose does not refer to wind speed, but only to the probability of wind in that direction regardless of its strength.
  • 10 m wind speed is the instantaneous mean speed in m/s. Note:
    • The peaks of the whiskers should not be interpreted as wind gusts.  The special atmospheric ensemble products related to gusts, such as gust probability charts, should be used.
  • Significant wave height is an instantaneous forecast value in metres.  It is estimate of the mean height of the highest one-third of the waves. This corresponds with international conventions.  Note:
    • The peaks of the whiskers should not be interpreted as peak wave heights.  ECWAM ensemble products for maximum wave height and the corresponding wave period should be used ("maximum individual wave height" is available from MARS).
  • Mean wave direction is the mean direction of propagation of the waves, based on a weighted average of the wave spectrum.  Distribution roses for wave direction are created similarly to those for wind direction (see above).  Note:
    • Directions are shown in accordance with oceanographic convention which is the direction towards which waves are propagating (eg wave direction of 180° means waves are propagating towards the south).  This is opposite to the way in which wind direction is displayed (eg 180°means the wind is blowing from the south).
    • Significant wave heights are shown by the colouring of each octant according to the adjacent scale and the probability of the significant wave height is shown by the area of each colour (See Fig8.1.6.2). 
  • Mean wave period is an instantaneous forecast value in seconds.  The mean period presented corresponds to the ““energy period””.  The key point for users to note is that more weight is given to low frequency waves containing swell than to high frequency waves.

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 Fig8.1.6.2: 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 control and CONTROL -10 WAM 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). 

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