Improved 12-month ahead predictions obtained by applying an adaptative Kalman filter to the primary McNish and Lincoln (ML) prodictions from WDC-SILSO. This technique improves the approximation of the smoothed monthly sunspot number over the last 6 months, i.e. the interval between the last available smoothed value of the sunspot number and the current month of the prediction.
T. Podladchikova, R. Van der Linden, 2012: "A Kalman Filter Technique for Improving Medium-Term Predictions of the Sunspot Number". Solar Physics. DOI: 10.1007/s11207-011-9899-y https://link.springer.com/article/10.1007/s11207-011-9899-y