Magnetograms at τ = 1 (left), smoothed vertical velocity at τ = 1 (middle), and vertical flow velocity in 8 Mm depth (right) for three different times during the spot formation phase (t = 24, 28, and 32 hr). In the velocity plots black contours indicate vertical magnetic field with more than 1.5 kG in the photosphere. Positive velocity values (blue colors) indicate upflows.