Once plotted on a map, an analysis of isotachs (lines of equal wind speeds) can be accomplished. Isotachs are particularly useful in diagnosing the location of the jet stream on upper level constant pressure charts, usually at or above the 300 hPa level.

The flags and pennants point to the low pressure, so it is possible to determine at which hemisphere the station is standing. The barbs in the figure at the right are located at the Northern Hemisphere, because