Figure 2. Regression and classification ANN performance . (a) Regression ANN and persistence model MJO prediction skill during winter (purple) and summer (green). A bivariate correlation coefficient (BCC) threshold of 0.5 denotes skill (dotted). (b) The classification ANN and persistence model accuracy during winter: black curves are accuracy across all days, and red curves are accuracy predicting only active MJO days. Shading indicates less than random chance (~11%). (c) As in panel (a), but for winter forecasts binned by observed initial MJO amplitude via the RMM amplitude ranges in the legend. (d) Winter classification ANN accuracy (top panel) and initial observed MJO amplitude (bottom panel) binned by ANN confidence (x -axis, in bins of width 0.05) at leads of 0, 5, 10, and 15 days. The black x’s indicate the one-to-one line.