Products based on an ensemble of forecasts providing an estimate of the reliability of a single forecast.
The purchase of the "Basic Set" +72, +96, +120, +144, +168 hrs is a mandatory prerequisite for the purchase of time steps in the range 12 to 66 hours.
The following subsets are available from the ENSWAM:
 IVi: Wave fields
 IViia: Probabilities  Instantaneous weather events
 IViib: Probabilities  Averaged weather events
 IViiia: Extreme Forecast Index (EFI) 1day ranges
 IViiib: Shift of Tails (SOT) 1day ranges
Dissemination schedule
based IVi: Wave fields
(dissemination data stream indicator = W)
12 UTC based Forecast time  00 UTC based Time available  12 UTC based Time Available 

Forecast Day 0  07:00  19:00 
Forecast Day 10  07:40  19:40 
Forecast Day 15  08:00  20:00 
Derived products Step 0 to 240  07:41  19:41 
Derived products Step 246 to 360  08:01  20:01 
IVii: Probabilities
(dissemination data stream indicator = U)
12 UTC based Forecast time  Time Available  00 UTC based Forecast time  Time available 

Forecast Day 0  19:00  Forecast Day 0  07:00 
Forecast Day 10  19:40  Forecast Day 10  07:40 
Forecast Day 15  20:00  Forecast Day 15  08:00 
Derived products Step 0 to 240  19:41  Derived products Step 0 to 240  07:41 
Derived products Step 246 to 360  20:01  Derived products Step 246 to 360  08:01 
IViii: Extreme Forecast Index & Shift of Tails
(dissemination data stream indicator = U)
12 UTC based Forecast time  Time Available  00 UTC based Forecast time  Time available 

Forecast Day 0  19:00  Forecast Day 0  07:00 
Forecast Day 10  19:40  Forecast Day 10  07:40 
Forecast Day 15  20:00  Forecast Day 15  08:00 
Derived products Step 0 to 240  19:41  Derived products Step 0 to 240  07:41 
Derived products Step 246 to 360  20:01  Derived products Step 246 to 360  08:01 
Parameters
All tables are sortable by column. Use your browser search for specific parameters.
Terms convention  

(inv)  Invariant field. If requested these parameters can be provided free of charge 
IVi: Wave fields
Short Name  ID  Long Name  Description  Units  Additional information 

weta  140098  Wave induced mean sea level correction  m  
wraf  140099  Ratio of wave angular and frequency width  dimensionless  
wnslc  140100  Number of events in freak waves statistics  dimensionless  
utaua  140101  Ucomponent of atmospheric surface momentum flux  N m**2  
vtaua  140102  Vcomponent of atmospheric surface momentum flux  N m**2  
utauo  140103  Ucomponent of surface momentum flux into ocean  N m**2  
vtauo  140104  Vcomponent of surface momentum flux into ocean  N m**2  
wphio  140105  Wave turbulent energy flux into ocean  W m**2  
wefxm  140112  Wave energy flux magnitude  This parameter is the amount of energy from ocean/sea waves which are generated by local winds and associated with swell. It is the magnitude of the energy flux per unit length of wave crest, also known as the wave power per unit length of wave crest. In deep water, the wave energy flux magnitude can be estimated from the mean wave period and the significant wave height. In the ECMWF Integrated Forecasting System, it is calculated by integrating the full twodimensional wave spectrum multiplied by the wave group velocity (the velocity of the envelope of a group of waves of nearly equal frequencies). 
W m**1  
wefxd  140113  Wave energy flux mean direction  This parameter is the direction of the flux of energy of ocean/sea waves which are generated by local winds and associated with swell. It is the spectral mean direction calculated by integrating the full twodimensional wave energy spectrum multiplied by the wave group velocity (the velocity of the envelope of a group of waves of nearly equal frequencies). The units are degrees true which means the direction relative to the geographic location of the north pole. It is the direction that waves are coming FROM, so zero means 'coming from the north' and 90 'coming from the east'. 
Degree true  
h1012  140114  Significant wave height of all waves with periods within the inclusive range from 10 to 12 seconds  This parameter represents the average height of the highest third of surface ocean/sea waves that have a period between 10 and 12 seconds. It includes all waves generated by local winds and associated with swell. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. More strictly, this parameter is four times the square root of the integral over all directions of the twodimensional wave spectrum and all frequencies between 1/12 and 1/10 hertz (i.e. periods between 10 and 12 seconds). See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
h1214  140115  Significant wave height of all waves with periods within the inclusive range from 12 to 14 seconds  This parameter represents the average height of the highest third of surface ocean/sea waves that have a period between 12 and 14 seconds. It includes all waves generated by local winds and associated with swell. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. More strictly, this parameter is four times the square root of the integral over all directions of the twodimensional wave spectrum and all frequencies between 1/14 and 1/12 hertz (i.e. periods between 12 and 14 seconds). See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
h1417  140116  Significant wave height of all waves with periods within the inclusive range from 14 to 17 seconds  This parameter represents the average height of the highest third of surface ocean/sea waves that have a period between 14 and 17 seconds. It includes all waves generated by local winds and associated with swell. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. More strictly, this parameter is four times the square root of the integral over all directions of the twodimensional wave spectrum and all frequencies between 1/17 and 1/14 hertz (i.e. periods between 14 and 17 seconds). See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
h1721  140117  Significant wave height of all waves with periods within the inclusive range from 17 to 21 seconds  This parameter represents the average height of the highest third of surface ocean/sea waves that have a period between 17 and 21 seconds. It includes all waves generated by local winds and associated with swell. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. More strictly, this parameter is four times the square root of the integral over all directions of the twodimensional wave spectrum and all frequencies between 1/21 and 1/17 hertz (i.e. periods between 17 and 21 seconds). See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
h2125  140118  Significant wave height of all waves with periods within the inclusive range from 21 to 25 seconds  This parameter represents the average height of the highest third of surface ocean/sea waves that have a period between 21 and 25 seconds. It includes all waves generated by local winds and associated with swell. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. More strictly, this parameter is four times the square root of the integral over all directions of the twodimensional wave spectrum and all frequencies between 1/25 and 1/21 hertz (i.e. periods between 21 and 25 seconds). See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
h2530  140119  Significant wave height of all waves with periods within the inclusive range from 25 to 30 seconds  This parameter represents the average height of the highest third of surface ocean/sea waves that have a period between 25 and 30 seconds. It includes all waves generated by local winds and associated with swell. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. More strictly, this parameter is four times the square root of the integral over all directions of the twodimensional wave spectrum and all frequencies between 1/30 and 1/25 hertz (i.e. periods between 25 and 30 seconds). See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
sh10  140120  Significant wave height of all waves with period larger than 10s  This parameter represents the average height of the highest third of surface ocean/sea waves that have a period of longer than 10 seconds. It includes all waves generated by local winds and associated with swell. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. More strictly, this parameter is four times the square root of the integral over all directions of the twodimensional wave spectrum and over frequencies less than 0.1 hertz (i.e. periods longer than 10 seconds). See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
swh1  140121  Significant wave height of first swell partition  This parameter represents the average height of the highest third of surface ocean/sea waves associated with the first swell partition. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. In many situations, swell can be made up of different swell systems, for example, from two distant and separate storms. To account for this, the swell spectrum is partitioned into up to three parts. The swell partitions are labelled first, second and third based on their respective wave height. Therefore, there is no guarantee of spatial coherence (the first might be from one system at one location and another system at the neighbouring location). See further information. More strictly, this parameter is four times the square root of the integral over all directions and all frequencies of the first swell partition of the twodimensional swell spectrum. The swell spectrum is obtained by only considering the components of the twodimensional wave spectrum that are not under the influence of the local wind. This parameter can be used to assess swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
mwd1  140122  Mean wave direction of first swell partition  This parameter is the mean direction of waves in the first swell partition. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. In many situations, swell can be made up of different swell systems, for example, from two distant and separate storms. To account for this, the swell spectrum is partitioned into up to three parts. The swell partitions are labelled first, second and third based on their respective wave height. Therefore, there is no guarantee of spatial coherence (the first swell partition might be from one system at one location and a different system at the neighbouring location). See further information. The units are degrees true which means the direction relative to the geographic location of the north pole. It is the direction that waves are coming FROM, so zero means 'coming from the north' and 90 'coming from the east'. 
degrees  
mwp1  140123  Mean wave period of first swell partition  This parameter is the mean period of waves in the first swell partition. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. In many situations, swell can be made up of different swell systems, for example, from two distant and separate storms. To account for this, the swell spectrum is partitioned into up to three parts. The swell partitions are labelled first, second and third based on their respective wave height. Therefore, there is no guarantee of spatial coherence (the first swell partition might be from one system at one location and a different system at the neighbouring location). See further information. 
s  
swh2  140124  Significant wave height of second swell partition  This parameter represents the average height of the highest third of surface ocean/sea waves associated with the second swell partition. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. In many situations, swell can be made up of different swell systems, for example, from two distant and separate storms. To account for this, the swell spectrum is partitioned into up to three parts. The swell partitions are labelled first, second and third based on their respective wave height. Therefore, there is no guarantee of spatial coherence (the second might be from one system at one location and another system at the neighbouring location). See further information. More strictly, this parameter is four times the square root of the integral over all directions and all frequencies of the first swell partition of the twodimensional swell spectrum. The swell spectrum is obtained by only considering the components of the twodimensional wave spectrum that are not under the influence of the local wind. This parameter can be used to assess swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
mwd2  140125  Mean wave direction of second swell partition  This parameter is the mean direction of waves in the second swell partition. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. In many situations, swell can be made up of different swell systems, for example, from two distant and separate storms. To account for this, the swell spectrum is partitioned into up to three parts. The swell partitions are labelled first, second and third based on their respective wave height. Therefore, there is no guarantee of spatial coherence (the second swell partition might be from one system at one location and a different system at the neighbouring location). See further information. The units are degrees true which means the direction relative to the geographic location of the north pole. It is the direction that waves are coming FROM, so zero means 'coming from the north' and 90 'coming from the east'. 
degrees  
mwp2  140126  Mean wave period of second swell partition  This parameter is the mean period of waves in the second swell partition. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. In many situations, swell can be made up of different swell systems, for example, from two distant and separate storms. To account for this, the swell spectrum is partitioned into up to three parts. The swell partitions are labelled first, second and third based on their respective wave height. Therefore, there is no guarantee of spatial coherence (the second swell partition might be from one system at one location and a different system at the neighbouring location). See further information. 
s  
swh3  140127  Significant wave height of third swell partition  This parameter represents the average height of the highest third of surface ocean/sea waves associated with the third swell partition. Wave height represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. In many situations, swell can be made up of different swell systems, for example, from two distant and separate storms. To account for this, the swell spectrum is partitioned into up to three parts. The swell partitions are labelled first, second and third based on their respective wave height. Therefore, there is no guarantee of spatial coherence (the third might be from one system at one location and another system at the neighbouring location). See further information. More strictly, this parameter is four times the square root of the integral over all directions and all frequencies of the first swell partition of the twodimensional swell spectrum. The swell spectrum is obtained by only considering the components of the twodimensional wave spectrum that are not under the influence of the local wind. This parameter can be used to assess swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
mwd3  140128  Mean wave direction of third swell partition  This parameter is the mean direction of waves in the third swell partition. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. In many situations, swell can be made up of different swell systems, for example, from two distant and separate storms. To account for this, the swell spectrum is partitioned into up to three parts. The swell partitions are labelled first, second and third based on their respective wave height. Therefore, there is no guarantee of spatial coherence (the third swell partition might be from one system at one location and a different system at the neighbouring location). See further information. The units are degrees true which means the direction relative to the geographic location of the north pole. It is the direction that waves are coming FROM, so zero means 'coming from the north' and 90 'coming from the east'. 
degrees  
mwp3  140129  Mean wave period of third swell partition  This parameter is the mean period of waves in the third swell partition. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. In many situations, swell can be made up of different swell systems, for example, from two distant and separate storms. To account for this, the swell spectrum is partitioned into up to three parts. The swell partitions are labelled first, second and third based on their respective wave height. Therefore, there is no guarantee of spatial coherence (the third swell partition might be from one system at one location and a different system at the neighbouring location). See further information. 
s  
wss  140207  Wave Spectral Skewness  This parameter is a statistical measure used to forecast extreme or freak ocean/sea waves. It describes the nature of the sea surface elevation and how it is affected by waves generated by local winds and associated with swell. Under typical conditions, the sea surface elevation, as described by its probability density function, has a near normal distribution in the statistical sense. However, under certain wave conditions the probability density function of the sea surface elevation can deviate considerably from normality, signalling increased probability of freak waves. This parameter gives one measure of the deviation from normality. It is a measure of the asymmetry of the probability density function of the sea surface elevation. So, a positive/negative skewness (typical range 0.2 to 0.12) means more frequent occurrences of extreme values above/below the mean, relative to a normal distribution. 
dimensionless  
wstar  140208  Free convective velocity over the oceans  This parameter is an estimate of the vertical velocity of updraughts generated by free convection. Free convection is fluid motion induced by buoyancy forces, which are driven by density gradients. The free convective velocity is used to estimate the impact of wind gusts on ocean wave growth. It is calculated at the height of the lowest temperature inversion (the height above the surface of the Earth where the temperature increases with height). This parameter is one of the parameters used to force the wave model, therefore it is only calculated over water bodies represented in the ocean wave model. It is interpolated from the atmospheric model horizontal grid onto the horizontal grid used by the ocean wave model. 
m s**1  
rhoao  140209  Air density over the oceans  This parameter is the mass of air per cubic metre over the oceans, derived from the temperature, specific humidity and pressure at the lowest model level in the atmospheric model. This parameter is one of the parameters used to force the wave model, therefore it is only calculated over water bodies represented in the ocean wave model. It is interpolated from the atmospheric model horizontal grid onto the horizontal grid used by the ocean wave model. 
kg m**3  
phiaw  140211  Normalized energy flux into waves  This parameter is the normalised vertical flux of energy from wind into the ocean waves. A positive flux implies a flux into the waves. The energy flux has units of Watts per metre squared, and this is normalised by being divided by the product of air density and the cube of the friction velocity. 
dimensionless  
phioc  140212  Normalized energy flux into ocean  This parameter is the normalised vertical flux of turbulent kinetic energy from ocean waves into the ocean. The energy flux is calculated from an estimation of white capping waves across the surface of the ocean. A white capping wave is one that appears white at its crest as it breaks, due to air being mixed into the water. When waves break in this way, there is a transfer of energy from the waves to the ocean. A negative flux implies a flux from the waves into the ocean. The energy flux has units of Watts per metre squared, and this is normalised by being divided by the product of air density and the cube of the friction velocity. 
dimensionless  
tauoc  140214  Normalized stress into ocean  This parameter is the normalised surface stress, or momentum flux, from the air into the ocean due to turbulence at the airsea interface and breaking waves. It does not include the flux used to generate waves. The ECMWF convention for vertical fluxes is positive downwards. The stress has units of Newtons per metre squared, and this is normalised by being divided by the product of air density and the square of the friction velocity. 
dimensionless  
ust  140215  Ucomponent stokes drift  This parameter is the eastward component of the surface Stokes drift. The Stokes drift is the net drift velocity due to surface wind waves. It is confined to the upper few metres of the ocean water column, with the largest value at the surface. For example, a fluid particle near the surface will slowly move in the direction of wave propagation. 
m s**1  
vst  140216  Vcomponent stokes drift  This parameter is the northward component of the surface Stokes drift. The Stokes drift is the net drift velocity due to surface wind waves. It is confined to the upper few metres of the ocean water column, with the largest value at the surface. For example, a fluid particle near the surface will slowly move in the direction of wave propagation. 
m s**1  
tmax  140217  Period corresponding to maximum individual wave height  This parameter is the period of the expected highest individual wave within a 20minute time window. It can be used as a guide to the characteristics of extreme or freak waves. Wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. Occasionally waves of different periods reinforce and interact nonlinearly giving a wave height considerably larger than the significant wave height. If the maximum individual wave height is more than twice the significant wave height, then the wave is considered to be a freak wave. The significant wave height represents the average height of the highest third of surface ocean/sea waves, generated by local winds and associated with swell. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived statistically from the twodimensional wave spectrum. See further information. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. 
s  
hmax  140218  Maximum individual wave height  This parameter is an estimate of the height of the expected highest individual wave within a 20 minute time window. It can be used as a guide to the likelihood of extreme or freak waves. The interactions between waves are nonlinear and occasionally concentrate wave energy giving a wave height considerably larger than the significant wave height. If the maximum individual wave height is more than twice the significant wave height, then the wave is considered as a freak wave. The significant wave height represents the average height of the highest third of surface ocean/sea waves, generated by local winds and associated with swell. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived statistically from the twodimensional wave spectrum. See further information. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. 
m  
wmb  140219  Model bathymetry  This parameter is the depth of water from the surface to the bottom of the ocean. It is used by the ocean wave model to specify the propagation properties of the different waves that could be present. Note that the ocean wave model grid is too coarse to resolve some small islands and mountains on the bottom of the ocean, but they can have an impact on surface ocean waves. The ocean wave model has been modified to reduce the wave energy flowing around or over features at spatial scales smaller than the grid box. 
m  
mp1  140220  Mean wave period based on first moment  This parameter is the reciprocal of the mean frequency of the wave components that represent the sea state. All wave components have been averaged proportionally to their respective amplitude. This parameter can be used to estimate the magnitude of Stokes drift transport in deep water. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). Moments are statistical quantities derived from the twodimensional wave spectrum. 
s  
mp2  140221  Mean zerocrossing wave period  This parameter represents the mean length of time between occasions where the sea/ocean surface crosses mean sea level. In combination with wave height information, it could be used to assess the length of time that a coastal structure might be under water, for example. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). In the ECMWF Integrated Forecasting System this parameter is calculated from the characteristics of the twodimensional wave spectrum. 
s  
wdw  140222  Wave spectral directional width  This parameter indicates whether waves (generated by local winds and associated with swell) are coming from similar directions or from a wide range of directions. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). Many ECMWF wave parameters (such as the mean wave period) give information averaged over all wave frequencies and directions, so do not give any information about the distribution of wave energy across frequencies and directions. This parameter gives more information about the nature of the twodimensional wave spectrum. This parameter is a measure of the range of wave directions for each frequency integrated across the twodimensional spectrum. This parameter takes values between 0 and the square root of 2. Where 0 corresponds to a unidirectional spectrum (i.e., all wave frequencies from the same direction) and the square root of 2 indicates a uniform spectrum (i.e., all wave frequencies from a different direction). 
dimensionless  
p1ww  140223  Mean wave period based on first moment for wind waves  This parameter is the reciprocal of the mean frequency of the wave components generated by local winds. All wave components have been averaged proportionally to their respective amplitude. This parameter can be used to estimate the magnitude of Stokes drift transport in deep water associated with wind waves. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time.This parameter takes account of windsea waves only. Moments are statistical quantities derived from the twodimensional wave spectrum. 
s  
p2ww  140224  Mean wave period based on second moment for wind waves  This parameter is equivalent to the zerocrossing mean wave period for waves generated by local winds. The zerocrossing mean wave period represents the mean length of time between occasions where the sea/ocean surface crosses a defined zeroth level (such as mean sea level). The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. Moments are statistical quantities derived from the twodimensional wave spectrum. 
s  
dwww  140225  Wave spectral directional width for wind waves  This parameter indicates whether waves generated by the local wind are coming from similar directions or from a wide range of directions. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of windsea waves only. Many ECMWF wave parameters (such as the mean wave period) give information averaged over all wave frequencies and directions, so do not give any information about the distribution of wave energy across frequencies and directions. This parameter gives more information about the nature of the twodimensional wave spectrum. This parameter is a measure of the range of wave directions for each frequency integrated across the twodimensional spectrum. This parameter takes values between 0 and the square root of 2. Where 0 corresponds to a unidirectional spectrum (i.e., all wave frequencies from the same direction) and the square root of 2 indicates a uniform spectrum (i.e., all wave frequencies from a different direction). 
dimensionless  
p1ps  140226  Mean wave period based on first moment for swell  This parameter is the reciprocal of the mean frequency of the wave components associated with swell. All wave components have been averaged proportionally to their respective amplitude. This parameter can be used to estimate the magnitude of Stokes drift transport in deep water associated with swell. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time.This parameter takes account of all swell only. Moments are statistical quantities derived from the twodimensional wave spectrum. 
s  
p2ps  140227  Mean wave period based on second moment for swell  This parameter is equivalent to the zerocrossing mean wave period for swell. The zerocrossing mean wave period represents the mean length of time between occasions where the sea/ocean surface crosses a defined zeroth level (such as mean sea level). The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. Moments are statistical quantities derived from the twodimensional wave spectrum. 
s  
dwps  140228  Wave spectral directional width for swell  This parameter indicates whether waves associated with swell are coming from similar directions or from a wide range of directions. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of all swell only. Many ECMWF wave parameters (such as the mean wave period) give information averaged over all wave frequencies and directions, so do not give any information about the distribution of wave energy across frequencies and directions. This parameter gives more information about the nature of the twodimensional wave spectrum. This parameter is a measure of the range of wave directions for each frequency integrated across the twodimensional spectrum. This parameter takes values between 0 and the square root of 2. Where 0 corresponds to a unidirectional spectrum (i.e., all wave frequencies from the same direction) and the square root of 2 indicates a uniform spectrum (i.e., all wave frequencies from a different direction). 
dimensionless  
swh  140229  Significant height of combined wind waves and swell  This parameter represents the average height of the highest third of surface ocean/sea waves generated by wind and swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. More strictly, this parameter is four times the square root of the integral over all directions and all frequencies of the twodimensional wave spectrum. See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
mwd  140230  Mean wave direction  This parameter is the mean direction of ocean/sea surface waves. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is a mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use this type of wave information when designing structures in the open ocean, such as oil platforms, or in coastal applications. The units are degree true which means the direction relative to the geographic location of the north pole. Zero means 'coming from the north' and 90 'coming from the east'. 
Degree true  
pp1d  140231  Peak wave period  This parameter represents the period of the most energetic ocean waves generated by local winds and associated with swell. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is calculated from the reciprocal of the frequency corresponding to the largest value (peak) of the frequency wave spectrum. The frequency wave spectrum is obtained by integrating the twodimensional wave spectrum over all directions. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. 
s  
mwp  140232  Mean wave period  This parameter is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is a mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further documentation. This parameter can be used to assess sea state and swell. For example, engineers use such wave information when designing structures in the open ocean, such as oil platforms, or in coastal applications. 
s  
cdww  140233  Coefficient of drag with waves  This parameter is the resistance that ocean waves exert on the atmosphere. It is sometimes also called a 'friction coefficient'. It is calculated by the wave model as the ratio of the square of the friction velocity, to the square of the neutral wind speed at a height of 10 metres above the surface of the Earth. The neutral wind is calculated from the surface stress and the corresponding roughness length by assuming that the air is neutrally stratified. The neutral wind is, by definition, in the direction of the surface stress. The size of the roughness length depends on the sea state. 
dimensionless  
shww  140234  Significant height of wind waves  This parameter represents the average height of the highest third of surface ocean/sea waves generated by the local wind. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of windsea waves only. More strictly, this parameter is four times the square root of the integral over all directions and all frequencies of the twodimensional windsea wave spectrum. The windsea wave spectrum is obtained by only considering the components of the twodimensional wave spectrum that are still under the influence of the local wind. See further documentation. This parameter can be used to assess windsea waves. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
mdww  140235  Mean direction of wind waves  The mean direction of waves generated by local winds. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time.This parameter takes account of windsea waves only. It is the mean over all frequencies and directions of the total windsea wave spectrum. See further information. The units are degrees true which means the direction relative to the geographic location of the north pole. It is the direction that waves are coming FROM, so zero means 'coming from the north' and 90 'coming from the east'. 
degrees  
mpww  140236  Mean period of wind waves  This parameter is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea generated by local winds, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of windsea waves only. It is the mean over all frequencies and directions of the total windsea spectrum. See further information. 
s  
shts  140237  Significant height of total swell  This parameter represents the average height of the highest third of surface ocean/sea waves associated with swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of total swell only. More strictly, this parameter is four times the square root of the integral over all directions and all frequencies of the twodimensional total swell spectrum. The total swell spectrum is obtained by only considering the components of the twodimensional wave spectrum that are not under the influence of the local wind. See further documentation. This parameter can be used to assess swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
m  
mdts  140238  Mean direction of total swell  This parameter is the mean direction of waves associated with swell. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time.This parameter takes account of all swell only. It is the mean over all frequencies and directions of the total swell spectrum. See further information. The units are degrees true which means the direction relative to the geographic location of the north pole. It is the direction that waves are coming FROM, so zero means 'coming from the north' and 90 'coming from the east'. 
degrees  
mpts  140239  Mean period of total swell  This parameter is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea associated with swell, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of all swell only. It is the mean over all frequencies and directions of the total swell spectrum. See further information. 
s  
msqs  140244  Mean square slope of waves  This parameter can be related analytically to the average slope of combined windsea and swell waves. It can also be expressed as a function of wind speed under some statistical assumptions. The higher the slope, the steeper the waves. This parameter indicates the roughness of the sea/ocean surface which affects the interaction between ocean and atmosphere. See further information. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived statistically from the twodimensional wave spectrum. 
dimensionless  
wind  140245  10 metre wind speed  This parameter is the horizontal speed of the 'neutral wind', at a height of ten metres above the surface of the Earth. The units of this parameter are metres per second. The neutral wind is calculated from the surface stress and the corresponding roughness length by assuming that the air is neutrally stratified. The neutral wind is, by definition, in the direction of the surface stress. The size of the roughness length depends on sea state. This parameter is the wind speed used to force the wave model, therefore it is only calculated over water bodies represented in the ocean wave model. It is interpolated from the atmospheric model's horizontal grid onto the horizontal grid used by the ocean wave model. 
m s**1  
dwi  140249  10 metre wind direction  This parameter is the direction from which the 'neutral wind' blows, in degrees clockwise from true north, at a height of ten metres above the surface of the Earth. The neutral wind is calculated from the surface stress and roughness length by assuming that the air is neutrally stratified. The neutral wind is, by definition, in the direction of the surface stress. The size of the roughness length depends on the sea state. This parameter is the wind direction used to force the wave model, therefore it is only calculated over water bodies represented in the ocean wave model. It is interpolated from the atmospheric model's horizontal grid onto the horizontal grid used by the ocean wave model. 
degrees  
2dfd  140251  2D wave spectra (single)  The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter represents the wave energy for each frequency and direction at each model grid point i.e., it describes the contribution to the frequency and direction of the twodimensional wave spectrum. Strictly, this parameter is the base ten logarithm of the spectral density of ocean waves in two dimensions (across the horizontal surface of the ocean). Therefore, all values (except missing data) need to be raised to the power of ten to give the spectral density. 'Missing data' is indicated by a value of 0. The spectral density describes the combination of waves with different heights, lengths and directions. See further documentation. 
m**2 s radian**1  
wsk  140252  Wave spectral kurtosis  This parameter is a statistical measure used to forecast extreme or freak ocean/sea waves. It describes the nature of the sea surface elevation and how it is affected by waves generated by local winds and associated with swell. Under typical conditions, the sea surface elevation, as described by its probability density function, has a near normal distribution in the statistical sense. However, under certain wave conditions the probability density function of the sea surface elevation can deviate considerably from normality, signalling increased probability of freak waves. This parameter gives one measure of the deviation from normality. It shows how much of the probability density function of the sea surface elevation exists in the tails of the distribution. So, a positive kurtosis (typical range 0.0 to 0.06) means more frequent occurrences of very extreme values (either above or below the mean), relative to a normal distribution. 
dimensionless  
bfi  140253  BenjaminFeir index  This parameter is used to calculate the likelihood of freak ocean waves, which are waves that are higher than twice the mean height of the highest third of waves. Large values of this parameter (in practice of the order 1) indicate increased probability of the occurrence of freak waves. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived from the statistics of the twodimensional wave spectrum. More precisely, it is the square of the ratio of the integral ocean wave steepness and the relative width of the frequency spectrum of the waves. Further information on the calculation of this parameter is given in Section 10.6 of the ECMWF Wave Model documentation. 
dimensionless  
wsp  140254  Wave spectral peakedness  This parameter is a statistical measure used to forecast extreme or freak waves. It is a measure of the relative width of the ocean/sea wave frequency spectrum (i.e., whether the ocean/sea wave field is made up of a narrow or broad range of frequencies). The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). When the wave field is more focussed around a narrow range of frequencies, the probability of freak/extreme waves increases. This parameter is Goda's peakedness factor and is used to calculate the BenjaminFeir Index (BFI). The BFI is in turn used to estimate the probability and nature of extreme/freak waves. 
dimensionless 
IVii: Probabilities
Product resolution: 0.25° x 0.25° lat/long grid or any multiple thereof (global or subarea)
Forecast time step  Base time  

T+24 to T+360h  12hourly  00 UTC and 12 UTC 
Forecast ranges 
Base time 

2 day period covering 120h < T ≤ 168h 
00 UTC and 12 UTC 
3 day period covering 168h < T ≤ 240h 
00 UTC and 12 UTC 
5 day period covering 120h < T ≤ 240h 
00 UTC and 12 UTC 
5day periods: 240h < T ≤ 360h 
00 UTC and 12 UTC 
IViia: Probabilities  Instantaneous weather events
Short Name  ID  Long Name  Description  Units  Additional information 

swhg2  131074  Significant wave height of at least 2 m  This parameter gives the probability (in %) that the significant wave height will be 2 m or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a significant wave height of 2 m or above. The significant wave height represents the average height of the highest third of surface ocean/sea waves generated by wind and swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. More strictly, this significant wave height is four times the square root of the integral over all directions and all frequencies of the twodimensional wave spectrum. See further documentation. Significant wave height can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
%  
swhg4  131075  Significant wave height of at least 4 m  This parameter gives the probability (in %) that the significant wave height will be 4 m or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a significant wave height of 4 m or above. The significant wave height represents the average height of the highest third of surface ocean/sea waves generated by wind and swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. More strictly, this significant wave height is four times the square root of the integral over all directions and all frequencies of the twodimensional wave spectrum. See further documentation. Significant wave height can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
%  
swhg6  131076  Significant wave height of at least 6 m  This parameter gives the probability (in %) that the significant wave height will be 6 m or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a significant wave height of 6 m or above. The significant wave height represents the average height of the highest third of surface ocean/sea waves generated by wind and swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. More strictly, this significant wave height is four times the square root of the integral over all directions and all frequencies of the twodimensional wave spectrum. See further documentation. Significant wave height can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
%  
swhg8  131077  Significant wave height of at least 8 m  This parameter gives the probability (in %) that the significant wave height will be 8 m or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a significant wave height of 8 m or above. The significant wave height represents the average height of the highest third of surface ocean/sea waves generated by wind and swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. More strictly, this significant wave height is four times the square root of the integral over all directions and all frequencies of the twodimensional wave spectrum. See further documentation. Significant wave height can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
%  
mwpg8  131078  Mean wave period of at least 8 s  This parameter gives the probability (in %) that the mean wave period will be 8 s or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a mean wave period of 8 s or above. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived from the mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further information. 
%  
mwpg10  131079  Mean wave period of at least 10 s  This parameter gives the probability (in %) that the mean wave period will be 10 s or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a mean wave period of 10 s or above. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived from the mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further information. 
%  
mwpg12  131080  Mean wave period of at least 12 s  This parameter gives the probability (in %) that the mean wave period will be 12 s or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a mean wave period of 12 s or above. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived from the mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further information. 
%  
mwpg15  131081  Mean wave period of at least 15 s  This parameter gives the probability (in %) that the mean wave period will be 15 s or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a mean wave period of 15 s or above. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived from the mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further information. 
% 
IViib: Probabilities  Averaged weather events
Short Name  ID  Long Name  Description  Units  Additional information 

swhg2  131074  Significant wave height of at least 2 m  This parameter gives the probability (in %) that the significant wave height will be 2 m or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a significant wave height of 2 m or above. The significant wave height represents the average height of the highest third of surface ocean/sea waves generated by wind and swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. More strictly, this significant wave height is four times the square root of the integral over all directions and all frequencies of the twodimensional wave spectrum. See further documentation. Significant wave height can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
%  
swhg4  131075  Significant wave height of at least 4 m  This parameter gives the probability (in %) that the significant wave height will be 4 m or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a significant wave height of 4 m or above. The significant wave height represents the average height of the highest third of surface ocean/sea waves generated by wind and swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. More strictly, this significant wave height is four times the square root of the integral over all directions and all frequencies of the twodimensional wave spectrum. See further documentation. Significant wave height can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
%  
swhg6  131076  Significant wave height of at least 6 m  This parameter gives the probability (in %) that the significant wave height will be 6 m or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a significant wave height of 6 m or above. The significant wave height represents the average height of the highest third of surface ocean/sea waves generated by wind and swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. More strictly, this significant wave height is four times the square root of the integral over all directions and all frequencies of the twodimensional wave spectrum. See further documentation. Significant wave height can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
%  
swhg8  131077  Significant wave height of at least 8 m  This parameter gives the probability (in %) that the significant wave height will be 8 m or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a significant wave height of 8 m or above. The significant wave height represents the average height of the highest third of surface ocean/sea waves generated by wind and swell. It represents the vertical distance between the wave crest and the wave trough. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. More strictly, this significant wave height is four times the square root of the integral over all directions and all frequencies of the twodimensional wave spectrum. See further documentation. Significant wave height can be used to assess sea state and swell. For example, engineers use significant wave height to calculate the load on structures in the open ocean, such as oil platforms, or in coastal applications. 
%  
mwpg8  131078  Mean wave period of at least 8 s  This parameter gives the probability (in %) that the mean wave period will be 8 s or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a mean wave period of 8 s or above. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived from the mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further information. 
%  
mwpg10  131079  Mean wave period of at least 10 s  This parameter gives the probability (in %) that the mean wave period will be 10 s or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a mean wave period of 10 s or above. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived from the mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further information. 
%  
mwpg12  131080  Mean wave period of at least 12 s  This parameter gives the probability (in %) that the mean wave period will be 12 s or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a mean wave period of 12 s or above. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived from the mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further information. 
%  
mwpg15  131081  Mean wave period of at least 15 s  This parameter gives the probability (in %) that the mean wave period will be 15 s or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a mean wave period of 15 s or above. The wave period is the average time it takes for two consecutive wave crests, on the surface of the ocean/sea, to pass through a fixed point. The ocean/sea surface wave field consists of a combination of waves with different heights, lengths and directions (known as the twodimensional wave spectrum). This parameter is derived from the mean over all frequencies and directions of the twodimensional wave spectrum. The wave spectrum can be decomposed into windsea waves, which are directly affected by local winds, and swell, the waves that were generated by the wind at a different location and time. This parameter takes account of both. See further information. 
% 
IViiia: Extreme Forecast Index (EFI) 1day ranges
Short Name  ID  Long Name  Description  Units  Additional information 

maxswhi  132216  Maximum of significant wave height index  This parameter indicates how extreme the significant wave height is relative to the model climate. It is part of the ECMWF Extreme Forecast Index (EFI). Values range from 1 to +1.

(1 to 1) 
IViiib: Shift of Tails (SOT) 1day ranges
Short Name  ID  Long Name  Description  Units  Additional information 

maxswhi  132216  Maximum of significant wave height index  This parameter indicates how extreme the significant wave height is relative to the model climate. It is part of the ECMWF Extreme Forecast Index (EFI). Values range from 1 to +1.

(1 to 1) 
Last updated 09092020