Hurricane Irene presented a unique challenge to operational and experimental algorithms that produce quantitative precipitation estimates, including those using new dual-polarization (DP) technology. The National Severe Storms Laboratory's Storm-Scale Hydrometeorology group is working with the WSR-88D Radar Operations Center/Applications Branch to evaluate this new technology and is also developing an improved version of the DP algorithm. As such, several QPE algorithms including the legacy Precipitation Processing System, legacy DP, NSSL Prototype DP and next-generation QPE (Q2) were available during Irene in real time for comparison in order to identify performance issues and further enhancements.

Initial results indicate high rainfall efficiency with rain gauge amounts exceeding operational and research QPE tropical Z-R settings. Base radar reflectivity values ranged from 30-45 dBZ indicating that a “super-tropical” Z-R (or Zdr-R) relationship may be required for advanced QPE applications. This paper will provide an overall performance assessment and highlight the scientific challenges associated with QPE in extreme events such as Hurricane Irene.