McWilliams received his college degrees in Applied Mathematics: a B.S. (with honors) in 1968 from Caltech and a M.S. in 1969 and Ph.D. in 1971 from Harvard. After holding a Research Fellowship in Geophysical Fluid Dynamics at Harvard (1971-74), he worked in the Oceanography Section at the National Center for Atmospheric Research (NCAR), where he became a Senior Scientist in 1980. In 1994 he became the Louis B. Slichter Professor of Earth Sciences in the Department of Atmospheric and Oceanic Sciences and the Institute for Geophysics and Planetary Physics at UCLA, while retaining a part-time appointment at NCAR. In 2002, he was elected to the National Academy of Sciences.

McWilliams’ primary areas of scientific research are the fluid dynamics of Earth’s oceans and atmosphere, both their theory and computational modeling. Particular subjects include the maintenance of the general circulations; climate dynamics; geostrophically and cyclostrophically balanced (or slow manifold) dynamics in rotating, stratified fluids; vortex dynamics; planetary boundary layers; planetary-scale thermohaline convection; the roles of coherent structures in turbulent flows in geophysical and astrophysical regimes; numerical algorithms; statistical estimation theory; and coastal ocean modeling.

In the past several years he has helped develop a three-dimensional simulation model of the U.S. West Coast that incorporates physical oceanographic, biogeochemical, and sediment transport aspects of the coastal circulation. This model is being used to interpret coastal phenomena, diagnose historical variability in relation to observational data, and assess future possibilities.