We have characterized the behavior of transient eddies in the northern hemisphere of Mars through analysis of Radio Science (RS) occultation data from Mars Global Surveyor (MGS). The "weather" in the lowest scale height above the surface at 55¿N--80¿N is dominated by shallow, eastward moving baroclinic eddies distinguished by their intensity and coherence. The vertical structure of these eddies is fully resolved by the RS measurements, which also yield unique estimates of the near-surface meridional winds implied by geostrophic balance. We identified and characterized the most prominent eddies through space-time analysis of RS measurements of geopotential height at 610 Pa, a few kilometers above the surface. Eddy activity appears as well-defined modes with zonal wave numbers 1--3, and variations in the amplitudes of these modes tend to be anticorrelated so that a large amplitude in one mode is often accompanied by a small amplitude in the others. The wave number and period of the dominant mode shift at intervals of 30--50 sols. Eddy winds near the surface vary distinctively with season in response to changes in eddy amplitude and zonal wave number. The meridional winds peak sharply in two seasonal windows, one in early-to-middle autumn and the other in middle-to-late winter, separated by a lull around winter solstice. Comparisons with previous results reveal close connections with the transient eddies observed by the Viking Landers and with distinctive southward moving frontal dust storms observed by the MGS Mars Orbiter Camera.