How it's made: Your Questions on metocean models, answered

We go under the hood of weather forecasting in How It’s Made: The Ultimate Guide to Weather Forecasting. Through the guide and accompanying blog series, we explore the Five Categories that create an accurate, reliable forecast.

This post focuses in on Category Two of the How It's Made forecasting methodology: Metocean models

 

Download your copy of "How It’s Made: The Ultimate Guide to Weather Forecasting" below:


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

Models are computer programs in which the laws of physics, chemistry and fluid motion, and a coordinate system are considered. A modeler maps relevant properties of the earth onto a 2D/3D grid on which the model is then run.

Winds, heat transfer, solar radiation, relative humidity, and surface hydrology are calculated per grid cell, and the interactions with neighboring cells are used to predict future metocean properties. To make it even more complicated, each metocean model comes with its own characteristics, meaning there’s no such thing as the ultimate model. Therefore, metocean experts use a combination of models to optimize accuracy.
 

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 novel cloud infrastructure that enables us to quickly respond to customer requests. 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
 

 

What information do metocean models provide?
 

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, typically they work as follows:

Atmospheric models calculate temperature, relative humidity, wind, precipitation, heat transfer, solar radiation, and surface hydrology in each cell, with neighboring cells used to calculate future properties

Oceanographic models, for example, the spectral wave model, use wind, ice and current, and bathymetric data to predict waves on each cell of the grid

 

How do the metocean experts use metocean models?


 

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 special cases, it can be weeks or months ahead).

 

What are the limits of metocean models?

 

Arguably, the resolution for metocean models can be infinite, by taking into account all possible variables. But the computing power and investment required to support such a resolution would also need to be infinite. This is why numerical modeling is divided into:
 

Mesoscale modeling: uses either a global grid of the entire earth at a relatively low resolution (with data retrieved from external centers such as the UK Met Office) or a

regional grid which has a higher resolution and covers broader areas including mountain ranges

Microscale modeling: uses a feature resolving grid that models specific environmental properties that strongly affect forecasted parameters which aren’t in regional grids such as islands, sandbanks, and valleys

 

Resolution and physics are always limiting factors with the above, but reliable forecast results can be achieved by assimilating observations via the global grid.

 

External versus in-house metocean modeling

 

Businesses that outsource their forecasting via metocean models will usually benefit from global atmospheric operational datasets such as ECMWF (proprietary), UKMO (proprietary), and the NCEP GFS (open). A license fee is sometimes required to access those datasets, while others offer free data.

An external metocean modeling company will offer several benefits, including:

● (statistical) multi-model approaches that include aggregated values for 24-hours of precipitation and temperature;

● ensemble forecasts that aggregate 50 scenarios for lowest wind speed, temperature and precipitation amount (and more); and

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

 

When undertaking in-house metocean modeling, most commercial and government weather forecasting companies integrate one or more mesoscale and microscale modeling services into their end products. Raw data can also be obtained from other companies, but the quality of that data and service level agreements often vary wildly.

 

Despite this, and with the right assistance, that data can be made to work very well. For instance, wave spectra from the ECWMF are only available on a three- or six-hour basis, while an experienced company can take the raw data and use it to produce data that is available for every hour (or more frequently).

 

Metocean models are reliable, affordable and with the right dataset they can provide businesses with unique selling points regarding their forecasting abilities.

 

Download your copy of "How It’s Made: The Ultimate Guide to Weather Forecasting" below:


Download Now

 

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 novel cloud infrastructure that enables us to quickly respond to customer requests. 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