Global vs. Local MJO Forecast Skills

This presentation introduces a new measure of local MJO forecast skill in comparison to commonly used measure of global MJO forecast skill based on the Wheeler-Hendon RMM index. Local forecast skill is measured by timing, propagation speed, and strength of MJO convection or precipitation centers starting from the Indian Ocean. Using ECMWF forecast of the three MJO events during the DYNAMO field campaign as examples, we demonstrate that the quickest forecast error growth is in the systematic reduction of the strength and large ensemble spread in the propagation speed. From an application point of view, both global and local forecast skills are needed. But local skill sets a higher standard for evaluation of MJO forecast. It is also useful to quantify the fidelity of model simulations of individual MJO events.