Evaluation of Unified Forecast System Tropical Cyclone Quantitative Precipitation Forecasts

As the NOAA Unified Forecast System (UFS) advances towards operational implementation of two applications (Hurricane Application in 2023 and the Short-Range Weather (SRW) Application in 2024), it is important to understand the model performance for critical fields such as precipitation. Verification of tropical cyclone quantitative precipitation forecasts (QPF) not only informs improvements in process representation within models, but also helps evaluate and improve forecasts to mitigate the risks associated with extreme rainfall and flooding from landfalling tropical cyclones. Understanding model-based QPF over the ocean also provides important information regarding the forecast biases that may impact storm characteristics at the time of landfall. Additionally, a goal of the UFS is to support the development of a suite of physical parameterizations that can be applied with minimal modification across scales and applications. With this in mind, it is also important to understand the impact of physics suites on model QPFs.

This presentation will provide a comprehensive QPF evaluation of two UFS Hurricane Analysis and Forecast System version 1 (HAFSv1) configurations relative to performance of the operational Hurricane Weather Research and Forecast (HWRF) model, verified against Integrated Multi-satellitE Retrievals for GPM (IMERG) over water, and the Climatology-Calibrated Precipitation Analysis (CCPA) over land. In addition to standard QPF verification, evaluations using advanced methods such as track shifting, storm centric and object oriented verification will be shown using the enhanced Model Evaluation Tools (METplus). Differences between the HAFSv1 configurations will be explored in the context of different microphysics and planetary boundary layer schemes between the configurations. To further explore the impact of physics suites on the model QPF performance, case studies of several landfalling hurricane simulations (e.g. Laura 2020, Ian 2022) will be compared using multiple physics suites relevant for operations (i.e. Global Forecast System (GFS)v17 prototype 8, HAFS suite-1, HAFS suite-2, Rapid Refresh Forecast System (RRFS) version 1 beta, High Resolution Rapid Refresh (HRRR)), using the SRW Application.