<p>Observations of the boundary layer (BL) processes are analyzed in four shallow convective days (ShCu) and four shallow-to-deep convective days (ShDeep) using a suite of ground-based measurements from the second Intensive Operating Period as part of the Observation and Modeling of the Green Ocean Amazon (IOP2; GoAmazon 2014/5) Experiment. The BL stages in ShDeep days, from the nighttime to the cloudy mixing layer stage, are then described in comparison with ShCu days. Atmosphere thermodynamics and dynamics, environmental profiles, and surface fluxes were employed to compare these two distinct situations for each stage of the BL evolution. Particular attention is given to the morning transition stage, in which the BL changes from stable to unstable conditions in the early morning hours. Results show that the duration of the morning transition on ShDeep days decreases under high humidity and intense vertical wind shear. Higher humidity since nighttime not only contributes to lowering the cloud base during the rapid growth of the BL but also contributes to the balance between radiative cooling and turbulent mixing during nighttime, resulting in large sensible heat flux in the early morning. A large sensible heat flux promotes rapid growth of the well-mixed layer, thus favoring the deeper BL starting from around 08:00 LST. Under these conditions, turbulent mixing provides a lifting mechanism by which air parcels reach the lifting condensation level, leading to the formation of shallow cumulus clouds and their subsequent evolution into deep convective clouds.</p>