Figure 1. ANN model schematics . (a) The regression ANN; leftmost panels show a sample input of OLR and zonal wind at 850 hPa (u850) and 200 hPa (u200) from November 22, 2011. The input is passed through a 16-node hidden layer with a rectified linear unit (“ReLU”) activation function. The regression ANN outputs values of RMM1 and RMM2 at a single lead time, and separate ANNs are trained for leads from 0-20 days. An example 20-day ANN forecast (purple) versus observations (black) is shown in the rightmost panel. (b) The classification model schematic. Input is identical to the regression model, but the output is the probability the MJO is active in RMM Phase 1-8 or is inactive (“Phase 0”). An example forecast at a 10-day lead from November 22, 2011 is shown on the right.