Mechanisms governing the persistence and diurnal cycle of a heavy rainfall corridor

Despite the relatively modest CAPE, convection is favored by the large reductions in CIN along the vertical displacements and by high ambient midtropospheric relative humidity located above, which is influenced by persistent nightly convection in the region. Though internal feedbacks resulting from the large nightly spatial coherence of convection (including enhanced midtropospheric relative humidities and frontogenetic daytime sensible heat flux gradients owing to residual cloudiness) are favorable for maintaining the corridor, its persistence is most sensitive to large-scale external factors.

Here, changes to the intensity and position of the large-synoptic upper-tropospheric anticyclone are associated with changes in the frequency of strong LLJs and the surface frontal position, dramatically affecting the intensity and stationarity of the precipitation corridor.