Mesoscale Convective Complexes and thunderstorm events in the Alagoas State, the Northeast Brazil

Abstract

Forecast of the Mesoscale Convective Complexes (MCC) is extremely important for the social and economic contexts of the Alagoas State (Northeast Brazil (NEB)) since they can cause several adverse phenomena. Some examples of these phenomena are intense rainfall, thunderstorms, flooding, and landslide. The main aim of this study was to analyze a connection between thunderstorms and MCC in the Alagoas area during two years period (2013-2014). Following data and models were used: (1) Review of the National Centers for Environmental Prediction (NCEP); (2) The European Center for Medium-Range Weather Forecasts (ECMWF); (3) GOES-13 satellite images from the Brazilian Forecast and Climate Study Center (CPTEC); (4) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) and (5) Environmental and Water Resources Department of Alagoas (SEMARH). The MCC frequency between 2013 and 2014 was far lower related to the 2000-2010 period. Among the nine MCC cases observed, thunderstorms were reported twice. It was identified Direct influence of the Upper Tropospheric Cyclonic Vortex (UTCV) to the thunderstorms development was identified. This synoptic system is responsible for the numerous cases of storm in the NEB (Bashir et al., 2011). Thermodynamic study was based on the analysis of vertical profiles of temperature and humidity, forecasted up to 48 hours in advance. Forecast was elaborated used parcel trajectories from the HYSPLIT model in 10 standard levels. Vertical profiles with 12 h antecedence were considered satisfactory. Connections of the MCC development with the horizontal distribution of temperature and humidity (in the low and high levels) were studied. MCC formation and development occurred on the periphery of hot air core (up to 27°C) and relatively dry (80%). Temperatures decrease and there was no change in humidity at the time of MCC dissipation.