  In this paper we describe a model for the $(\ell=2, m=0)$ spherical harmonic
mode of the gravitational wave signal emitted by the coalescence of binary
black holes, in particular, spin-aligned systems. This mode can be viewed as
consisting of two components, gravitational wave memory and quasi-normal
ringdown, which are both included in our model. Depending on the parameters of
the binary and the sensitivity curve of the detector, but in particular for
high masses, the ringdown part can contribute significantly to the
signal-to-noise ratio. The model is constructed using the methods of the
phenomenological waveforms program, and is calibrated to public numerical
relativity data from the SXS waveforms catalog, with the analytical results
derived from the BMS balance laws. The code has been implemented as an
extension to the computationally efficient IMRPhenomTHM model, it can therefore
be used for computationally expensive applications such as Bayesian parameter
estimation. The region of validity of our model in the parameter space is given
by: $q\leq10$ and $\chi_{1},\chi_{2}\in[-1,1]$, and no restrictions apply in
terms of the length of the waveforms.
