Compared with Earth, Jupiter is absolutely filled with jets. We can describe the Jovian atmosphere using a number of well-studied equations and planetary theory, and jets are better understood than Jupiter’s vortices (the spots and swirls you see on its surface), but this is still a very active subject of study. We don’t really know why there are so many bands, or why the bands got there to begin with, or why they’re stable. We disagree about what controls their size, or even why they go in a particular direction, though models are able to reproduce the structure we see at the top of the atmosphere pretty well. Scientists have only recently been able to connect Jupiter’s deep interior convection and magnetic forces with the surface jets. Progress is hampered by the lack of observations of Jupiter’s deep interior, which makes modeling the Jovian atmosphere very difficult, though NASA’s Juno mission will be doing exactly that this summer (Juno arrives at Jupiter on July 4th!). Arriving at a description of Earth’s circulation required hundreds of years of study, plus thousands more of actually being on Earth, so for only 350 years of study, I would say Jovian meteorologists are doing a pretty good job.

What about exoplanets? Observing exoplanets as they transit across their stars can give us information on the atmosphere. From our great distance away, we can't see much spatial detail, but we can observe for a long time, meaning that we can get enough data points to start to get a rough map of an atmosphere. Directly observing jets is out of the question (for now!), but we may already be seeing the effects of jets. A key signature of jets is that they redistribute heat. Absent jets, planets are hot at the equator, cold at the poles, and hottest right around where the sun is shining. If we can see temperatures where they shouldn’t be, for example, warm near the poles or cold air near the equator, we can infer that a jet may be responsible. So provided that we can thermally image planets, we can start to ask questions about jets.