A weather model, also known as numerical weather prediction, is a complex algorithm run by supercomputers to try to predict future weather.

Here is a good write up of ** Numerical Weather Prediction**. Pasted below are a few key points:

We can construct a three-dimensional grid of the atmosphere and use these equations to create a mathematical model. If we plug data that we've gathered on its current state into our grid, we can then solve the equations to predict a future state -- numerical weather prediction.

The actual mathematics involved are beyond the scope of this FAQ. However, assuming you've already developed the mathematics for your model, the process goes something like this:

- First, settle on the area to be looked at and define a three-dimensional grid with an appropriate resolution (20 to 200 kilometers on a side, say, and going maybe 10 kilometers up).
- Then, gather weather readings (temperature, humidity, barometric pressure, wind speed and direction, precipitation, etc.) for each grid point.
- Run your assimilation scheme so the data you've gathered actually fits the model you've designed.
- Now, run your model by stepping it forward in time -- a few minutes, say.
- Go back and repeat step 2 through step 4 again.
- When you've finally stepped the model forward as far as your forecast outlook (from a day to maybe a week), publish your prediction to the world.
- And finally, analyze and verify how accurately your model predicted the actual weather. Revise it accordingly.

All that produces a numerical prediction.