Second harmonics intensity and spectra, emitted from solid Al target heated by obliquely incident p-polarized 1.5 ps Nd-laser pulse, are interpreted in the frame of 1D hydrodynamics model including resonance absorption, fast electron generation and transport and acceleration of ions. Second harmonics spectra reveal blue shift for laser intensity 10¹⁶ W/cm², while red shift is observed for laser intensity 10¹⁷ W/cm². It corresponds to a qualitative difference in the critical surface dynamics observed in simulations. A good agreement of simulation results with experiment is observed for the lower intensity while possible explanations of certain discrepancies for the higher intensity are proposed.