  Prediction of solar activity cycles is challenging because physical processes
inside the Sun involve a broad range of multiscale dynamics that no model can
reproduce and because the available observations are highly limited and cover
mostly surface layers. Helioseismology makes it possible to probe solar
dynamics in the convective zone, but variations in differential rotation and
meridional circulation are currently available for only two solar activity
cycles. It has been demonstrated that sunspot observations, which cover over
400 years, can be used to calibrate the Parker-Kleeorin-Ruzmaikin dynamo model,
and that the Ensemble Kalman Filter (EnKF) method can be used to link the
modeled magnetic fields to sunspot observations and make reliable predictions
of a following activity cycle. However, for more accurate predictions, it is
necessary to use actual observations of the solar magnetic fields, which are
available only for the last four solar cycles. In this paper I briefly discuss
the influence of the limited number of available observations on the accuracy
of EnKF estimates of solar cycle parameters, the criteria to evaluate the
predictions, and application of synoptic magnetograms to the prediction of
solar activity.
