  Insight into the formation and global distribution of cloud particles in
exoplanet atmospheres continues to be a key problem to tackle going into the
JWST era. Understanding microphysical cloud processes and atmospheric feedback
mechanisms in 3D has proven to be a challenging prospect for exoplaneteers. In
an effort to address the large computational burden of coupling these models in
3D simulations, we develop an open source, lightweight and efficient
microphysical cloud model for exoplanet atmospheres. `Mini-cloud' is a
microphysical based cloud model for exoplanet condensate clouds that can be
coupled to contemporary general circulation models (GCMs) and other time
dependent simulations. We couple mini-cloud to the Exo-FMS GCM and use a prime
JWST target, the hot Jupiter HAT-P-1b, as a test case for the cloud formation
module. After 1000+ of days of integration with mini-cloud, our results show a
complex 3D cloud structure with cloud properties relating closely the dynamical
and temperature properties of the atmosphere. Current transit and emission
spectra data are best fit with a reduced cloud particle number density compared
to the nominal simulation, with our simulated JWST NIRISS SOSS spectra showing
promising prospects for characterising the atmosphere in detail. Overall, our
study is another small step in first principles 3D exoplanet cloud formation
microphysical modelling. We suggest that additional physics not included in the
present model, such as coagulation, are required to reduce the number density
of particles to appropriately observed levels.
