The 2017 NOAA Hurricane Forecast Improvement Program (HFIP) Real-Time Experiments: Highlights on Hurricanes Harvey, Irma and Maria

A major component of NOAA’s Hurricane Forecast Improvement Program (HFIP) is the support of real-time experiments, called “Stream 2 activities”. The purpose of Stream 2 activities is to apply new or advanced science and technologies in an operational-equivalent setting with the purpose of identifying the research activities that are candidates for transition into NOAA operations. Candidates for operational transitions are primarily identified through the evaluation of track and intensity forecasts. The “jet” high-performance computing facility located in Boulder, CO serves as a primary resource for Stream 2 efforts. Highlighting the success of these efforts, HFIP Stream 2 activities have been responsible for all major research to operations (R2O) transitions related to the Hurricane Weather Research and Forecasting (HWRF) Model. In the 2017 hurricane season, two main Stream 2 activities were run in real-time to supplement the Global Forecast System (GFS) and HWRF: 1) the “basin-scale HWRF”, an advanced version of the HWRF system that is being developed at NOAA’s Hurricane Research Division of the Atlantic Oceanographic and Meteorological Laboratory and 2) the FV3-Global Forecast System, the next generation global prediction system being developed at NOAA’s Geophysical Fluid Dynamics Laboratory. Both HFIP experimental models showed significant track improvements over the parent models (GFS and HWRF). For instance the basin-scale HWRF was at least 10% better in terms of tracks when compared to HWRF as well as GFS for all major land-falling hurricanes in 2017 (Harvey, Irma and Maria). In this talk we will especially focus on the intensity and structure predictions from the 2-km runs of the basin-scale HWRF system for these land-falling hurricanes

For the first time, tail doppler radar observations from NOAA P3s and High-Density observations (HDOBS from P-3, C-130) were assimilated into the basin-scale HWRF for Harvey, Irma and Maria. This experimental HWRF configuration was the best NOAA model for Hurricane Harvey. The model captured accurately the rapid intensification (RI) event before landfall, and the slow and nearly stagnant motion of Harvey that resulted in record rainfall in and around Houston, Texas. In the case of Irma, the basin-scale HWRF forecasted the tracks, intensity changes associated with the terrain interactions over Espaniola, the large rainbands and the associated helicity over Florida near and at landfall very well. In the case of Maria, the basin-scale HWRF, again, captured the RI several cycles in advance. At the meeting apart from conventional verification, we will provide some details of the inner core structure and comparisons with aircraft observations for all the 3 cases. We will also discuss the challenges associated with structure and intensity predictions especially in context of the major lanfalling hurricanes in 2017 and provide recommendations for further improving tropical cyclone guidance.