  We present LyMAS2, an improved version of the "Lyman-{\alpha} Mass
Association Scheme" aiming at predicting the large-scale 3d clustering
statistics of the Lyman-{\alpha} forest (Ly-{\alpha}) from moderate resolution
simulations of the dark matter (DM) distribution, with prior calibrations from
high resolution hydrodynamical simulations of smaller volumes. In this study,
calibrations are derived from the Horizon-AGN suite simulations, (100 Mpc/h)^3
comoving volume, using Wiener filtering, combining information from dark matter
density and velocity fields (i.e. velocity dispersion, vorticity, line of sight
1d-divergence and 3d-divergence). All new predictions have been done at z=2.5
in redshift-space, while considering the spectral resolution of the SDSS-III
BOSS Survey and different dark matter smoothing (0.3, 0.5 and 1.0 Mpc/h
comoving). We have tried different combinations of dark matter fields and found
that LyMAS2, applied to the Horizon-noAGN dark matter fields, significantly
improves the predictions of the Ly-{\alpha} 3d clustering statistics,
especially when the DM overdensity is associated with the velocity dispersion
or the vorticity fields. Compared to the hydrodynamical simulation trends, the
2-point correlation functions of pseudo-spectra generated with LyMAS2 can be
recovered with relative differences of ~5% even for high angles, the flux 1d
power spectrum (along the light of sight) with ~2% and the flux 1d probability
distribution function exactly. Finally, we have produced several large mock
BOSS spectra (1.0 and 1.5 Gpc/h) expected to lead to much more reliable and
accurate theoretical predictions.
