Dynamics analyses are presented for the west Florida continental shelf response to upwelling favorable, alongshore or offshore winds using a three-dimensional, time-dependent, primitive equation model. These analyses complement the kinematics analyses of Li and Weisberg <1999>. Results are provided on four topics: (1) the response evolutions to quasi steady states, (2) the across-shelf distributions of the vertically integrated alongshore and across-shelf momentum balances, (3) the three-dimensional structures of the terms composing the momentum balance closures, and (4) the model sensitivity to vertical friction parameterization. The response evolution starts with a local wind-driven acceleration, and it transitions over the inner shelf into a primary balance between the pressure gradient, Coriolis, and vertical friction terms. Thus the inner shelf spin-up takes a classical Ekman-geostrophic route. The middle shelf takes longer because it also depends on coastal boundary effects, notably the partial closure of the domain in the south by the Florida Keys. The outer shelf never achieves a steady state because of topographic wave effects. Coastline and isobath geometries result in fully three-dimensional flow fields. Thus a two-dimensional model that ignores alongshore variations cannot account for the results obtained. The inner shelf is the transition region between Ekman and Ekman-geostrophic balances where the surface slope results from mass adjustments through overlapping surface and bottom Ekman layers. Across the inner shelf the vertically integrated momentum balance shows a gradual trade-off between the Coriolis, pressure gradient, and bottom friction terms, and with the inner shelf frictionally determined its scale is sensitive to vertical friction parameterization. ¿ 1999 American Geophysical Union