Severe Convection in Central Argentina: Storm Modes and Environments

Satellite evidence, including from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR), indicates that the convection in central Argentina is globally unique in its intense vertical structure, broad horizontal organization, and lightning production.  Many mesoscale convective systems (MCSs) propagate over long distances after they are commonly initiated in the foothills of the Andes and Sierras de Córdoba (SDC), a lesser mountain range east of the primary Andes Cordillera.  However, isolated convection also forms near and apart from the topography. This convection is known to produce copious hazardous weather in the form of large hail, damaging winds, flash flooding, and tornadoes, with strong regional variability in severe weather types observed between regions close and apart from the Andes. 

The unique convective characteristics and storm structures in the region have motivated RELMPAGO (Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations, translates to lightning flash in Spanish and Portuguese), a field campaign that is currently scheduled for November-December 2018.  In preparation for the field phase, we are investigating convective modes in this region as observed from extreme convective structures identified by the TRMM satellite and infrared satellite data over a period 1998-present.  A strong contrast in convective modes is seen between the regions in the immediate lee of the Andes and near and east of the SDC.  Reanalysis composites during TRMM-observed events reveal strong differences between these two regions in boundary layer properties, bulk shear, instability, and effective environmental helicity that are spatially related to the observed climatological differences in storm structures.  WRF simulations of selected archetypical events observed during the 2014 and 2015 warm seasons are examined in each of these regions to understand the pre-convective and during-event storm environments and storm lifecycles in these regions.  Comparisons of the simulations with radar data collected during these events is performed to understand the ability of WRF to capture the bulk structure of observed storm cases.