  Solar activity forecasting is an important topic for numerous scientific and
technological areas, such as space mission operations, electric power
transmission lines, power transformation stations and earth geophysical and
climatic impact. Nevertheless, the well-known difficulty is how to accurately
predict, on the basis of various recorded solar activity indices, the complete
evolution of future solar cycles, due to highly complex dynamical and
stochastic processes involved, mainly related to interaction of different
components of internal magnetic fields. There are two main distinct classes of
solar cycle prediction methods: the precursor-like ones and the
mathematical-numerical ones. The main characteristic of precursor techniques,
both purely solar and geomagnetic, is their physical basis. Conversely, the
non-precursor methods use different mathematical and/or numerical properties of
the known temporal evolution of solar activity indices to extract useful
information for predicting future activity. For current solar cycle #24 we
obtained fairly good statistical performances from both precursor and purely
numerical methods, such as the so-called solar precursor and nonlinear ones. To
further check the performances of these prediction techniques, we compared the
early predictions for the next solar cycle #25. Preliminary results support
some coherence of the prediction methods considered and confirm the current
trend of a relatively low solar activity.
