An Estimate for the Size of Sunspot Cycle 24

For the sunspot cycles in the modern era (cycle 10 to the present), the ratio of RZ(max)/RZ(36th month) equals 1.26±0.22, where RZ(max) is the maximum amplitude of the sunspot cycle using smoothed monthly mean sunspot number and RZ(36th month) is the smoothed monthly mean sunspot number 36 months after cycle minimum. For the current sunspot cycle 24, the 36th month following the cycle minimum occurred in November 2011, measuring 61.1. Hence, cycle 24 likely will have a maximum amplitude of about 77.0±13.4 (the one-sigma prediction interval), a value well below the average RZ(max) for the modern era sunspot cycles (about 119.7±39.5).