Aviation (AVN) Model

As the name suggests, the Aviation (AVN) model provides meteorological data of interest to pilots. The model uses the sigma coordinate system (as does NGM), and has 42 levels of vertical resolution (layering).

The AVN model (sometimes listed as AVN/MRF, where MRF stands for "medium range forecasting") is an example of a spectral model. The example shown on the right is a 500 mb height chart of the hemisphere. Consider the example of a hemispheric 500-hPa height field in the top portion of the graphic. If the height data are tabulated at 40 degrees North latitude every 10 degrees of longitude (represented at each yellow dot on the chart), there are 36 points around the globe. It takes a minimum of five to seven points to reasonably represent a wave and, in this case, five or six waves can be defined with the data. The locations of the wave troughs are shown in the top part as solid red lines.

This model gives forecast information out to 72 hours. These plots are updated once every 12 hours at roughly 2:00 EST, with plots available beginning at 12 hours in the future. The AVN is run four times daily, at 0000, 0600, 1200, and 1800 GMT.

Like NGM, AVN results are available as MOS data files. An example AVN MOS data set , with legend, is presented for your inspection (Source: NOAA National Weather Service).