The Madden-Julian Oscillation (MJO) is the most important mode of tropical intraseasonal variability with potentially important influences on extra-tropical medium-to-extended range weather forecasting, Asian-Australian monsoon activity, and even variability in the equatorial Pacific thermocline structure via its close association with westerly wind bursts. Convective anomalies associated with the MJO are most intense over the Indian and western Pacific Oceans, whereas in South America they are more significant over southeast Brazil. This study investigates the possibility that the oscillation can impact the skill of medium range weather forecasts over South America and in southeast Brazil in particular.
Outgoing Longwave Radiation (OLR) and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis for the period January 1985-February 1990 are used to identify and classify events according to the phase of the MJO. Fifty-day forecasts from the NCEP Medium Range Forecast (MRF) model during the Dynamical Extended Range Forecast (DERF) experiment of January 1985-December 1989 are used to investigate the skill of medium-range weather forecasts in South America.