Dual-polarization Radar Characteristics of Convection in Hawaii Observed During HERO

Convection in the Hawaiian Islands is often driven by mesoscale rather than synoptic scale processes, yet most observational platforms cannot capture these phenomena at adequate spatial and temporal scales. The lack of detailed observations has limited our understanding of how processes such as orographic forcing and land/sea interaction play a role in tropical precipitation formation. The deployment of the DOW7 mobile X-band dual-polarization radar with the National Science Foundation sponsored Hawaiian Educational Radar Opportunity (HERO) project in October 2013 provided a unique opportunity to collect high-resolution dual-polarization radar data on Oahu. The project lasted for three weeks, and in that time, a number of convective types including orographically forced trade wind showers and inter-island sea-breeze storms were observed. In one particular case, an evolving trade wind shower passed directly over the radar, allowing for very high resolution radar analysis of vertical motion and cumulus development. In another case, a weakened trade wind inversion allowed sea-breeze convection to develop in the central valley of Oahu. Observations of the entire lifecycle of a convective cell from initiation to dissipation were analyzed. The analyzed cell stayed primarily below the freezing level and generated significant precipitation in 30 minutes through the warm rain process, with reflectivity exceeding 50 dBZ. The radar observations were analyzed using contour frequency by altitude diagrams (CFADs), and probability distributions of reflectivity and differential reflectivity. Differences in the mesoscale convective forcing mechanisms deduced from the HERO observations will be discussed.