The challenges to our understanding of MJO physics and to our ability of predicting and simulating the MJO are far from being met. Current skills of MJO prediction are limited and the predictability potential of the MJO has yet been fully realized. Many global climate models still cannot produce realistic MJO signals or fail to produce any MJO signal at all. The reason for this model infidelity is not well understood. Competing explanations for the existence and variability of the MJO remain topics of active debates.
These unmet challenges nonetheless, exciting progress has been made in the past decade in observations, modeling, and theories of the MJO. Real and virtual field campaigns have collected observations with unprecedented details of MJO processes. Several multi-model projects have yielded immense numerical simulation output for dissecting model deficiencies responsible for the failure of reproducing and predicting the MJO. New theoretical explorations have allowed quantitative descriptions of multi-scale, nonlinear, stochastic, and moist processes of the MJO. A global cloud-permitting model has opened a new door to numerical investigation of the MJO without errors from cumulus parameterization. These and other advances have brought us into a golden age of the MJO study. With more innovative ideas, we can expect further breakthroughs during the coming decade in understanding MJO physics and predicting the MJO and its global impact.