A Guide to Using Weather Models

Written by Gavin White

Last updated 11/1/2023, 3:30:37 PM

Weather models are predictive computer outputs that meteorologists use to help forecast the weather. Any weather model has dozens of variables a forecaster may wish to look at, ranging from temperature and humidity to precipitation, wind, and other indices.

Interestingly, the world's most powerful supercomputers are dedicated to running and maintaining the many different weather models. These computers run the models on a set basis; some are run every hour and others every six hours. Some models are built for short-term forecasting, leading to more frequent runs, while others are designed for long-term prediction, leading to infrequent runs.

To use a forecast model, you need to know which one to choose from first. Let’s explore the three models you can explore with WeatherTAP!

[Click Here For an Accompanying Video Guide]

RAP

The Rapid Refresh model is a National Oceanic and Atmospheric Administration (NOAA) model designed to cover North America. The model is updated hourly and uses the most current conditions to initialize each model run. The RAP is most beneficial for short-range forecasting since it models up to 21 hours past the run time.

NAM

The North American Mesoscale Forecast System is operated by a subsidiary of NOAA, also designed for North America (as the name implies). The model is updated every six hours. The NAM outputs results for the next 84 hours (2.5 days), making it a good choice for medium-range forecasts.

GFS

The Global Forecast System is the crown jewel of NOAA’s weather models as it covers the entire globe. Like the NAM, the GFS is updated every six hours, however, its resolution (or level of detail) is significantly lower than the other models.

The GFS is a good choice to get a general idea for long-range forecasting, as each run models 16 days into the future.

Once you’ve decided which model is best suited for your decided timescale, you can choose which variable(s) to look at. There are dozens of options to choose from, but don’t fret as they each have a purpose!

Wind & Height

This section of options visualizes wind speed and direction at various pressure levels. Pressure levels are measured in millibars (MB) and are inversely correlated with height, so the closer to 1000 MB, the closer to the surface of the earth that data is. The other pressure levels are useful for identifying where areas of high and low pressure are or to evaluate troughs and ridges in the jet stream (example pictured below).