Ocean forecasting at the Met Office: What are ocean models?

Ocean models and observations play a key role in keeping people safe at sea, supporting emergency services, and helping scientists understand our changing climate. Ocean forecasting predicts aspects of seas behaviour both on and below the surface of the sea, such as sea surface temperatures, wave heights, and ocean currents. These forecasts are used by a wide range of marine users, from professional mariners and leisure sailors, to coastal flood warnings and marine emergency response services, government policymakers and science research. 

Our Ocean Forecasting Research and Development (OFRD) and Ocean, Cryosphere and Climate teams lead the way in building and running computer models that simulate the ocean. These models help us understand how the ocean moves, how it interacts with the atmosphere, and how marine ecosystems respond to changes. 

READ MORE: Why has it been so warm and humid recently?

One of our main tools is the Forecast Ocean Assimilation Model (FOAM). FOAM systems are run every day to produce forecasts for the global ocean and shelf seas in specific regions. It is built on a powerful modelling system called NEMO, which is used and developed by scientists across Europe. FOAM also uses a system called NEMOVAR to combine the model with observations of the real-world, like sea surface temperature and salinity, so the model reflects what’s actually happening in the ocean. This makes our forecasts more accurate and reliable. Our global ocean model is coupled with our global weather model so that weather forecasts make use of an accurate prediction of how sea-surface temperatures will change over the course of the forecast.

Monitoring

To help monitor and predict the seas around the UK we run a high-resolution model of the North-West European Shelf Seas. This model looks at the ocean in great detail, with a resolution of just 1.5 km. It can show small features like internal tides and swirling currents, which are important for predicting how heat and moisture move between the ocean and the atmosphere. These details help improve forecasts of sea temperatures and ocean mixing. Our forecasts of UK waters are augmented by a dedicated storm surge model, which is used to understand how weather affects the behaviour of the tide and is an essential tool in issuing warnings and taking action to prevent coastal flooding. 

Wave forecasting

For wave forecasting, we use a model called WAVEWATCH III. This model takes information from both ocean and weather models to predict how waves grow, propagate and decay. Waves, winds, and currents all affect each other. For example, rough seas can slow down winds and change how heat moves between the ocean and the air. Waves also influence ocean currents and how energy is transferred across the sea surface. Outputs from our wave models are essential for maritime safety forecasts. 

READ MORE: Observations: The foundation of accurate weather forecasting 

We also support the OSTIA system, which provides near real-time sea surface temperature data using satellite observations. OSTIA is especially useful in areas where we don’t have direct measurements from ships or buoys. This system helps improve weather forecasts and supports climate monitoring around the world. 

We also use advanced models to study marine ecosystems and how they respond to environmental changes: 

• MEDUSA is a model that looks at how climate change and ocean acidification affect plankton and ocean chemistry. It includes different sizes of plankton and tracks important elements like nitrogen, silicon, iron, and carbon. MEDUSA helps us understand how human activities are changing the ocean. 

• ERSEM, developed by Plymouth Marine Laboratory, is one of the most detailed models of marine ecosystems. It includes bacteria, several types of phytoplankton and zooplankton, and tracks nutrients like carbon, nitrogen, phosphorus, and silicate. ERSEM is useful for studying how marine life responds to changes in the environment. 

• HadOCC, developed at the Met Office Hadley Centre, focuses on how the ocean absorbs carbon dioxide. It helps us understand the natural carbon cycle and how human emissions are affecting it. HadOCC is used in climate research and helps inform future climate projections. 

Our ocean modelling work is part of the Copernicus Marine Service, which shares high-quality ocean data with the public. By working with international partners and using the latest science, the Met Office helps protect lives at sea and deepens our understanding of the Earth’s systems. 

Keep up to date with weather warnings, and you can find the latest forecast on our website, on YouTube, by following us on X and Facebook, as well as on our mobile app which is available for iPhone from the App store and for Android from the Google Play store.