HYSPLIT Forum: hysplitbbs.arl.noaa.gov

Can air move at a fixed altitude from the Northern Hemisphere to the Southern Hemisphere? This run shows that at an altitude of 4500 m, the trajectory crosses the equator line. So it's possible? Or is it an erroneous trajectory?

That will depend on the underlying meteorology. Evidently in your case there is a fair amount of vertical sheer at that location in the equator. HYSPLIT will only reflect what the meteorological data shows.