Forecasting Solar Cycle 25 with a Principled Bayesian Two-stage Statistical Model

We update the Bayesian analysis of sunspot numbers (SSNs) developed by Yu et al. prior to the peak of Solar Cycle 24 to account for the recalibration of the SSN index. We show that the model yields an accurate hindcast of Cycle 24 with the revised SSN, and use the data acquired since then to predict the strength and peak of Cycle 25. We predict the behavior of Cycle 25 to be moderate to weak, with a peak SSN of 120±27 to occur c. 2025 July (±7 months).