  We model the observed X-ray spectral continuum shape, ionic column densities,
and absorption measure distribution (AMD) of the warm absorber in the Seyfert
galaxy NGC 3783. We assume a photo-ionized medium with a uniform total
(gas+radiation) pressure. The irradiation causes the wind to be radiation
pressure compressed (RPC). We compare the observational characteristics derived
from the 900 ksec Chandra observation to radiative transfer computations in
pressure equilibrium using the radiative transfer code TITAN. We explore
different values of the ionization parameter xi of the incident flux and adjust
the hydrogen-equivalent column density, N_H0 of the warm absorber to match the
observed soft X-ray continuum. We derive theoretical column densities for a
broad range of ionic species of iron and neon and an AMD that we compare to the
observations. We find an extension of the degeneracy between xi and N_H0 for
the constant pressure models previously discussed for NGC 3783. Including the
ionic column densities of iron and neon in the comparison between observations
and data we conclude that a range of ionization parameters between 4000 and
8000 ergs cm/s is preferred. For the first time, we present theoretical AMD for
a constant pressure wind in NGC 3783 that correctly reproduces the observed
level and is in approximate agreement with the observational appearance of an
instability region. Using a variety of observational indicators, we confirm
that the X-ray outflow of NGC 3783 can be described as an RPC medium in
pressure equilibrium. The observed AMD agrees with a uniformly hot or a
uniformly cold thermal state. The measured ionic column densities suggest that
the wind tends to the uniformly cold thermal state. The occurrence of thermal
instability in the warm absorber model may depend on the computational method
and the spatial scale on which the radiative transfer is solved.
