Simulated Secondary Eyewall in Operational HWRF

Recent understanding of the secondary eyewall phenomena, including its frequency of existence and the dynamics of its formation and evolution, is used to evaluate HWRF performance. The HWRF model is now integrated in real time in all hurricane basins of the world and its skill continues to improve in terms of storm intensity and track errors. With the work presented here we aim to set the foundation for a physical-process-based evaluation of the model relevant in the most intense storms.

It is shown that operational HWRF is capable of generating secondary eyewalls. We discuss the relatively rarity of these structures in the model. Some characteristics of secondary eyewalls in deterministic and ensemble integrations and some comparisons with observations are presented and analyzed. We pay special attention to Edouard 2014, a storm that exhibited a secondary eyewall whose life cycle was monitored with unprecedented data density during the NASA field campaign Hurricane Severe Storm Sentinel (HS3). We harvest the unprecedented quality of the observational dataset as a unique opportunity to evaluate model performance. We assess HWRF ability to capture the secondary eyewall and the physics governing its emergence and evolution.