Marine Weather Dashboard update: 2d spectral forecast and confidence index

Wed 26 June 2024

3 minutes read

New spectral forecast plots

To make our Marine Weather Dashboard as configurable and user friendly as possible, we are continuously improving the dashboard, developing new features, and improving existing functionalities. Introducing the 2d spectra forecast and a new index for forecast confidence. 

Spectral forecast

In our regular marine weather forecasts, Infoplaza represents ocean conditions in a simplified way. The sea state is assumed to consist of swell and wind waves. We recently added an option for clients to visualize a second swell system when present. Although very handy, in the end it is still a simplification.  

In reality the sea state consists of many wave systems, each having its own characteristic wave period and direction. These wave systems can be selected and grouped in order to yield meaningful parameters like wind waves, first swell, second swell and total swell. This results in so-called wave partitions

Each wave partition has its own set of characteristics, like mean and peak wave period and a significant wave height. The significant wave height is described as the average height of the highest one-third of waves in a partition. 

The total sea state can also be interpreted as a partition (grouping sea and all swells together), producing overall/total parameters like (total) significant wave height, overall peak period and overall mean wave direction. 

To accurately visualize all wave partitions, it requires the use of 2-dimensional spectral data. A 2D wave spectrum provides a detailed view of how wave energy is distributed across different wave frequencies (and thus periods) and directions. This information is invaluable for numerous offshore activities, including vessel operations, workability assessments, and safety procedures.  

By analysing the spectrum and the dominant wave directions we can determine where most of the energy is concentrated. This analysis also helps us to differentiate between swell (waves with a longer period generated by distant weather systems) and sea waves (waves with a shorter period, generated by local winds).  

For this purpose, Infoplaza has developed an interactive graphical method to visualize the spectral data available for your forecast location in our Marine Weather Dashboard.   

Visualization of wave energy

The visualizations in the Marine Weather Dashboard consist of:

  • A 3D plot showing the normalized wave energy as a function of the period and time.
  • A polar plot depicting the full wave spectrum for the selected time step, adding directional information.
  • A graph showing the normalized wave energy for your forecast location as a function of time.


All plots are interactive; using the slider in the bottom plot will indicate the respective elements and values in the other plots. 

The polar plot on the upper right adds directional information. This particular plot indicates two wave systems, with the rings indicating the wave period associated with this system.  One coming from the NW, and a second system coming from the NNE. It's also possible to download the raw data or to take a screenshot of the plots.

How we made the confidence index

Next, we've added a confidence index. Our index is calculated using a method that analyses the dispersion among ensemble predictions for 10-meter winds at every time step. The idea is straightforward: if the ensemble members vary widely (high dispersion), it signals low agreement among the models, leading to lower confidence in the forecast. Conversely, low dispersion indicates a strong consensus, which translates to higher confidence. This confidence index is then integrated into internal systems, allowing forecasters to adjust it based on their expertise and real-time observations.

Focus on wind

The emphasis on 10-meter wind speeds stems from its critical role in indicating broader weather patterns. Wind speeds reflect changes in atmospheric pressure systems, which in turn affect weather conditions. Variability in wind speeds can cause fluctuations in wave heights and temperatures, among other factors. Thus, confidence in wind speed forecasts serves as a reliable proxy for overall forecast confidence.

How it should be interpreted: confidence vs risk

Right above the risk indicator in  the Marine Weather Forecast, we will show the confidence of the forecast with 3 strips. 1 means low confidence, 2 means medium confidence, and 3 means high confidence.

Although the forecast confidence and risk levels in Marine Weather Dashboard are not directly linked, they are related. A period of high confidence means there it is highly likely that wind speed will turn out to be close to the forecast value. Thresholds are based on wind derived parameters. Therefore, it can be assumed the confidence in wind and wave parameters reaching that threshold level is similar to the overall confidence.

However, situations may arise that require a more nuanced interpretation.
For the night to Tuesday 26th, the threshold is orange. However, the wind speed is only 1 kt below the red threshold. The forecast confidence in this case is high, but it is very likely that the wind speed will exceed the red threshold by then, at least at times.  

From complexity to clarity

Our Marine Weather Dashboard provides complex information in clear weather presentations. See what it can do for your operations. You can test the new features in the dashboard right away: 

Go to dashboard

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