Metocean Models for the Offshore Industry, Explained

At an offshore wind farm located off the Belgian coast, sandbanks can cause high or long waves to break early, or induce waves to bend. These conditions make it harder to predict wave height, which is a real challenge for offshore projects in the area.

In the past, forecasts have been up to half a meter off because global wave models do not account for the sandbanks. This situation causes a challenge for vessels working close to their safety threshold.

When faced with challenges like this, the weather experts utilize metocean models to solve the problem. But, before we explore how the experts faced this challenge, let’s first explain what metocean models are and how they’re typically used by the experts.

 

How do the metocean experts use metocean models?

 

Meteorological and oceanographic models (metocean models) help experts forecast the conditions in the atmosphere and ocean over the coming hours, days, and weeks.

 

Metocean models use a coordinate system to map the earth onto a geospatial grid of latitude and longitude coordinates. This mapping includes properties like elevation, land-use, and the depth of water in oceans, seas, or lakes. Different models have different use-cases. For example, a spectral wave model uses wind, ice and current, and bathymetric data to predict waves on each cell of the grid.

 

"MeteoGroup provides tailored metocean forecast and historical datasets at any desired resolution and area on the globe. For that purpose, we make use of a new cloud infrastructure that enables us to respond to customer requests quickly. We owe ourselves to provide the best quality datasets, assessed against both our own station observation network (including public observations) and customer observation data. "

Dr Hugo Hartman,

Senior Meteo Scientist
MeteoGroup

 

By using the coordinate system to map the earth onto a grid, metocean models can be used by the experts to provide:

 

● Analyzed metocean conditions: these are the actual environmental state and latest observations for a specific point in time.

 

● Forecasted metocean conditions: these follow the analyzed conditions and are usually provided in the coming hours or days (though, in individual cases, it can be weeks or months ahead).

 

External Metocean models: What You Need to Know

 

External metocean models offer a range of different datasets. Weather companies will buy specific datasets, depending on their requirements.

External metocean models data is a key component of your weather forecast. Data from the models contributes to long-term forecasts. In offshore, this information is used by bidding companies during tenders to state when they would be able to undertake the work, within the constraints of the likely conditions.

External metocean models also support near real-time monitoring of the weather. This insight is essential for companies to keep project operations on schedule, ensure crew safety, and equipment maintenance.

But the data from the external models alone is not enough. A specialist weather company will advise you on how to use the model data. Plus, you can understand how to avoid bad decisions made when using misinterpreted model output data. A specialist weather company will offer several key benefits, including:

● (statistical) multi-models approaches, enhancing data from external providers;

● ensemble forecasts that aggregate 50 scenarios for probabilistic forecasting and to estimate risk and confidence to the forecasts; and

● two- or three-year archives of model forecasts.

 

In-House Metocean Modelling: What You Need to Know

 

External datasets, which are readily available in the market, are a valuable part of the forecaster's toolkit. However, they are just part of the puzzle. For example, wave spectra from ECWMF (an external model provider) are available every 3 to 6 hours.

But this might not be the required temporal resolution for your specific use case. In-house models can provide a higher resolution with insights for every hour - or even intra-hourly. The in-house models can also provide spatial resolution down to hundreds of meters.

 

"Modeling is both an art and a science. Where science delivers the empirical formula that forms the basis of the models themselves, it is up to the metocean modeler to simplify the complex world into an optimal configuration that ensures maximum quality while using as little resources as possible."

Sander Hulst
Senior Oceanographic Researcher

 

What is the difference between external and in-house metocean models?

 

In some use-cases, external datasets alone are not enough. They need additional inputs to solve the challenge that the customer is facing. Custom model configurations allow experts to select source terms (physical equations) and grid resolutions for that particular use case. To translate global data to your specific area of interest, the experts nest one or more feature-resolving grids in regional grids and then the regional grids in the global grids. We call this physical downscaling, an alternative to statistical downscaling.

 

How do the experts create a numerical metocean model?

 

Reliable forecasts are essential but complicated to produce. Taking the example of a specific oceanographic / wave model, we can see how the experts both produce the model and apply it to real-life situations.

Returning to our offshore wind farm example, to provide an accurate forecast in such a challenging location, it required the development of an in-house model using an innovative approach. By coupling atmospheric forcing with in-house wave models, it not only looks at the conditions at sea but also incorporates the atmospheric winds that drive the waves. Furthermore, it includes detailed tidal information, a prerequisite when working in shallow water. The model was calibrated both with local observations (in-situ) and remote sensing data. The model runs on a cloud-based High-Performance Cluster. This approach ensures there's always enough computing power for it to run and new models can be set up for any desired offshore operational location around the world.

 

What is the added value of in-house metocean models?

 

Different models have different strengths. Where a coarse model is set up to perform well in the deep ocean, a more detailed model is required closer to shore.

 

The advantage of in-house modeling experts means that different models can be coupled: the output from one becoming the input for another. For instance, a regional WAVEWATCHIII model can be fed surface wind data computed by a regional WRF domain, of which both receive boundary conditions from a global grid.

 

Think about offshore companies that need to plan operations in marginal weather conditions. They benefit from specific inhouse models and combinations. In this case, a SWAN model, run on a high-resolution grid, can take spectral wave data from the regional WAVEWATCHIII, surface winds from WRF, tidal data from harmonic components, and ocean circulation data from Mercator, to accurately capture, for instance, the wave-current interactions over complex seafloor features. The resulting dataset can provide unique insights into reigning and future conditions. These types of modeling are also crucial for innovative blue energy developments that depend on accurate tide and wave power data.

 

Accessing just the insight you need

 

In-house models are built for specific use cases or locations. They aim to increase the forecast value parameters of specific data points, for example data points relating to waves for near-shore work or specific offshore activities like survey, heavy lifting, pipe, and cable laying in commissioning to decommissioning phases across the different projects.

 

It’s about supporting the end user at all stages of their project with the data that they need. For offshore companies for example, this typically means using coarse data for the tender phase, with detailed studies used for the design phase and then using the same model grids for the operation and decommissioning phases.

 

Working with the experts, who know the models and your business, ensures that the guidance and advice you receive are tailored to your situation, site condition and requirements. You can focus on your priorities, confident that you have access to near real-time insight into how the weather and site conditions are developing.

 

Want to learn more? Visit our Offshore Knowledge Base.

 

Visit Offshore Knowledge Base

MeteoGroup provides tailored metocean forecast and historical datasets at any desired resolution and area on the globe. For that purpose, we make use of a new cloud infrastructure that enables us to respond to customer requests quickly. We owe ourselves to provide the best quality datasets, assessed against both our own station observation network (including public observations) and customer observation data.

Dr Hugo Hartman,

Senior Meteo Scientist
MeteoGroup