Sunspot Activity Running Well Above Forecast in October 2021

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The sunspot number for early October is around 50 which is well above the projected value based on the Sep. 10, 2021 forecast by NASA. In fact, the observation is above the 95th percentile forecast. Conservative forecasts for solar cycle 25 project a similar sunspot number at solar maxima in 2024-25 to the past solar peak occurring twice in 2011-12 and 2013-14. However, based on early trends, solar maximum for 2024-25 could be much stronger.

Discussion: The sunspot value for October 2021 is near 50 and well above the projected values from the September 10th forecast including the 95th percentile curve (Fig. 1). Forecasts vary for peak intensity of solar cycle projected to occur ins 2024-2025. The most conservative forecast which favors another relatively inactive solar maximum, similar to the solar cycle 24 peak is provided by NASA and indicates a maximum value of 115-120 (Fig. 2). Other forecasts are less conservative (140 in Fig. 1) while the upper limit forecast would feature an all-time record. So far, solar cycle intensity is well above the forecast projection.

Fig. 1: Probabilistic sunspot number forecast for solar cycle 25. Note that the October 2021 value is running much higher than the 95th percentile projection. Also note that a sunspot number of 240 at solar peak would be an allt0time record.  

Fig. 2: The NASA sunspot number forecast for solar cycle 25 and current monthly observation plot.