Multiple theories predict the existence of prograde fluid jets in the solar tachocline. We find helioseismic evidence of a prograde jet near 60° latitude in N and S hemispheres that persists through almost all of the current solar cycle. This evidence favors a hydrodynamic origin for the jet, from global instability of the differential rotation of the tachocline. We see no evidence for jets that migrate toward the equator with the advancing solar cycle, which tends to rule out jets associated with toroidal field bands in the tachocline.