A prediction for the 25th solar cycle maximum amplitude

The minimum-maximum method, belonging to the precursor class of the solar activity forecasting methods, is based on a linear relationship between relative sunspot number in the minimum and maximum epochs of solar cycles. In the present analysis, we apply a modified version of this method using data not only from the minimum year, but also from a couple of years before and after the minimum. The revised 13-month smoothed monthly total sunspot number data set from Sunspot Index and Long-term Solar Observations/SIDC is used. Using data for solar cycle nos. 1-24 the largest correlation coefficient (CC) is obtained when correlating activity level 3 years before solar cycle minimum with the subsequent maximum (CC=0.82), independent of inclusion or exclusion of the solar cycle no. 19. For the next solar maximum of the cycle no. 25, we predict: Rmax=121 +/- 33. Our results indicate that the next solar maximum (of the cycle no. 25) will be of the similar amplitude as the previous one, or even something lower. This is in accordance with the general middle-term lowering of the solar activity after the secular maximum in the 20th century and consistent with the Gleissberg period of the solar activity. The reliability of the "3 years before the minimum" predictor is experimentally justified by the largest CC and verified with the Student t-test. It is satisfactorily explained with the two empirical well-known findings: the extended solar cycle and the Waldmeier effect. Finally, we successfully reproduced the maxima of the last four solar cycles, nos. 21-25, using the 3 years before the minimum method.