The importance of past MJO activity in determining the future state of the midlatitude circulations on S2S timescales

The Madden Julian oscillation is one of the dominant predictability source on subseasonal to seasonal (S2S) timescales. Previous diagnostic and prediction studies have demonstrated the impact of present state of MJO on the future evolution and predictability of extratropical circulations. However, what in unclear is the accumulated influence of past MJO activities on these analyses. In this study, a linear baroclinic model (LBM) and a simple machine learning algorithm: logistic regression model are used to examine the importance of past MJO activity in determining the future state of extratropical circulations. By increasing the complexity of logistic regression model with additional MJO information, we demonstrate that the past 15 days play dominate role in determining the MJO teleconnections 15 days into the future. The result is supported by the ensemble LBM simulations. In this presentation, we further show that only specific MJO phases benefit from the past 15 days while others do not and the physical basis responsible for this result is provided.