  A longstanding mystery about Jupiter has been the straightness and steadiness
of its weather-layer jets, quite unlike terrestrial strong jets with their
characteristic unsteadiness and long-wavelength meandering. The problem is
addressed in two steps. The first is to take seriously the classic
Dowling-Ingersoll (DI) 1-1/2-layer scenario and its supporting observational
evidence, pointing toward deep, massive, zonally-symmetric zonal jets in the
underlying dry-convective layer. The second is to improve the realism of the
model stochastic forcing used to represent the effects of Jupiter's moist
convection as far as possible within the 1-1/2-layer dynamics. The real moist
convection should be strongest in the belts where the interface to the deep
flow is highest and coldest, and should generate cyclones as well as
anticyclones with the anticyclones systematically stronger. The new model
forcing reflects these insights. Also, it acts quasifrictionally on large
scales to produce statistically steady turbulent weather-layer regimes without
any need for explicit large-scale dissipation, and with weather-layer jets that
are approximately straight thanks to the influence of the deep jets, allowing
shear stability despite nonmonotonic potential-vorticity gradients when the
Rossby deformation lengthscale is not too large. Moderately strong forcing
produces chaotic vortex dynamics and realistic belt-zone contrasts in the
model's convective activity, through an eddy-induced sharpening and
strengthening of the weather-layer jets relative to the deep jets, tilting the
interface between them. Weak forcing, for which the only jet-sharpening
mechanism is the passive (Kelvin) shearing of vortices (as in the "CE2" or
"SSST" theories), produces unrealistic belt-zone contrasts.
