Extreme Precipitation Events in the Northeast Brazil during the winters of 2022 and 2023

This study aims to evaluate the synoptic conditions responsible for two extreme precipitation events development that occurred in the same region on the east coast of Northeast Brazil (NEB) in two different years, on July 1, 2022 (185 mm/24h), and July 7, 2023 (213 mm/24h). These events are becoming increasingly frequent in all regions of Brazil, especially in areas with high population density, associated with significant material and human losses, emphasizing the significance of a deeper comprehension of these events. ERA5 global reanalysis data have been used for synoptic and vertical structure evaluation as a first analysis step. Infrared GOES-16 satellite images have been used to monitor the cloudiness development. Pluviometric stations were used to document accumulated precipitation caused by these events. The following step will consist of conducting very high-resolution simulations using the Model for Prediction Across Scales (MPAS) to assess its ability to represent the circulation patterns associated with the analyzed extreme precipitation events. Both analyzed cases occurred along the eastern coast of the NEB, specifically over the Alagoas state, and were triggered by the same synoptic-scale system, the Easterly Wave Disturbances (EWDs). The trough axis penetrating the study area was observed on both examined dates, with a very characteristic relative vorticity of this tropical disturbance. Despite satellite images in the IR channel indicating lower cloud top temperatures in the first case, thermodynamic diagram data showed a greater vertical development of cloudiness in the second case. Distinct situations were observed when analyzing moisture transport convergence fields. In the first event, moisture convergence intensified over 12 hours, while in the second event, moisture convergence over Alagoas was evident throughout the entire day. This variation can be attributed to the intensification of the subtropical anticyclone during the extreme precipitation event in July 2023, which intensified moisture transport in the region. In general, moisture convergence resulted from the high flow of moisture prevailing over the region combined with upward movements caused by the trough present at low levels, which combined with local factors in the region such as topography, contributed to the increase in rainfall over the study area in both analyzed cases.