Wind vector outputs from a Farsite run are a compilation of all the different wind grids used in the run. Only the individual wind cells used for each timestep perimeter are shown as vectors. You can save the entire set of wind grids from a Farsite run with the Save Source Grids As command, this creates two files, a multi-band GeoTIFF format file and a XML file which contains the metadata for the individual bands.
The multi-band GeoTIFF file contains two bands for each Farsite timestep, a wind speed band, and a direction band. As a result the wind speed bands are odd numbered and the direction bands even numbered. The wind speed units in the saved GeoTIFF file will match whatever is selected in the ♦Wind Vector item.
Example of .XML format file containing metadata for wind grids stored in the multi-band GeoTIFF file.