What are computer models and what do their abbreviations stand for?

Computer models are the main tools that meteorologists and forecasters use to predict the weather over the next several days. Some of these computer models have the ability to show weather conditions 2-3 weeks in advance although the accuracy of the model is greatly reduced after just 3 days in advance.

A computer model is essentially built from advanced mathematical equations of the atmosphere and oceans. Current weather conditions are fed into the model, and it will then simulate how the weather will evolve over time. Computer models have different strengths, weaknesses, and biases when it comes to handling certain weather situations.

There are 4 main computer models that meteorologists and forecasters use. Each one has an abbreviation and below you can see what the abbreviations stand for:

GFS (Global Forecast System): The GFS model is a coupled weather forecast model, composed of four separate models that work together to provide an accurate picture of weather conditions. The GFS covers the entire globe down to a horizontal resolution of 28 km.

NAM (North American Mesoscale): The NAM is a regional weather forecast model covering North America down to a horizontal resolution of 12 km. Dozens of weather parameters are available from the NAM grids, from temperature and precipitation to lightning and turbulent kinetic energy.

GEM (Global Environmental Multiscale Model): The Canadian Meteorological Center produces a global model run twice daily. It is run out to 240 hours in advance.

ECMWF (European Centre for Medium-Range Weather Forecasts): ECMWF aims to provide accurate medium-range global weather forecasts out to 15 days. You will often here this computer model referred to as the "EURO" model. The model was quite famous during the 2012 Atlantic hurricane season when, at one point, it was the only model to show the odd left hand turn track that Hurricane Sandy took toward the New Jersey coastline. It also has a track record of high accuracy days in advance with regards to severe weather events and nor'easters.

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