Mesoscale analysis of heavy rainfall episodes from SoWMEX/TiMREX

Each period is about 5-6 days long with episodic heavy rainfall events within. These events are shown to correspond primarily to periods when well-defined frontal boundaries are established near the coast.

The boundaries are typically 1 km deep or less and feature contrasts of virtual temperature of only 2°-3°C. Yet, owing to the extremely moist condition of the upstream conditionally unstable air, these boundaries appear to exert a profound influence on convection initiation or intensification near the coast. Furthermore, the boundaries, once established, are long lived, possibly reinforced through cool downdrafts and prolonged by the absence of diurnal heating over land in generally cloudy conditions.