PNNL

Abstract

Deep convection initiated under different large-scale environments exhibit different precipitation features and interact with local meteorology and surface properties in distinct ways. Here, we analyze the characteristics and spatiotemporal patterns of different types of convective systems over southeastern Texas using 13-year high-resolution observations and reanalysis data. We find that mesoscale convective systems (MCSs) contribute significantly to both mean and extreme precipitation in all seasons, while isolated deep convection (IDC) play a role in intense precipitation during summer and fall. Using self-organizing maps (SOM), we found that convection can occur under unfavorable conditions without large-scale lifting and moisture convergence. In spring, fall and winter, frontal-related large-scale meteorological patterns (LSMPs) characterized by baroclinic waves and low-level moisture convergence act as primary triggers for convection, while the remaining storms are associated with an anticyclone pattern and orographic lifting. In summer, IDC are mainly associated with front-related and anticyclones LSMPs, while MCSs occur more in frontal-related LSMPs. We further tracked the lifecycle of MCSs and IDC using the Flexible Object Tracker algorithm over the southeastern Texas. The average lifetime of MCSs is 11.8 times of IDCs. MCSs frequently initiate west of Houston, travelling eastward for around 8 hours to southeast Texas, while IDC initiate locally. The average duration of MCSs in southeast Texas is 6.1 hours, approximately 4.1 times the duration of IDC. Diurnally, the initiation of convection associated with favorable LSMPs pick at 1100 UTC, 3 hours earlier than those associated with anticyclones.