July 27, 2021 - 2:00 pm
July 27, 2021 - 3:00 pm
CategoriesSchool of Meteorology (Defense)
School of Meteorology MS Thesis Defense
Impact of Assimilating Ground-Based and Airborne Radar Observations for the Analysis and Prediction of the Eyewall Replacement Cycle of Hurricane Matthew (2016) using HWRF Hybrid 3DEnVar System
Tuesday, July 27th
Video call link: https://meet.google.com/esv-acdr-moh
Or dial: (US) +1 414-909-4922 PIN: 657 493 298#
Eyewall replacement cycles (ERC) are common dynamical processes in mature tropical cyclones (TCs) that can result in quick changes to the storm’s intensity and wind field size. As the resolution of tropical cyclone models and the data assimilation (DA) techniques used to initialize them continue to improve, accurate initializations of concentric eyewall (CE) structure and forecasts for these events are important for the overall improvement of TC intensity forecasts. In this study, the analysis and prediction of Hurricane Matthew’s (2016) ERC is examined using HWRF and a Hybrid 3D Ensemble-Variational DA scheme. Four experiments performing hourly cycling from 1500 UTC October 6 to 1500 UTC October 7 are performed, assimilating differing sets of inner-core doppler radar observations, including Tail-Doppler Radar (TDR) and coastal Ground-Based Radar (GBR) radial velocity observations. The primary scientific objective of this study is to assess the impacts of assimilating GBR and TDR radial velocity observations individually, as well as in combination, on the analysis and forecast of Matthew’s ERC.
Results show that the accuracy of Matthew’s analyses and subsequent forecasts throughout the cycling are highly dependent on the start and duration of inner core doppler radar observation availability. Experiments assimilating GBR observations make quick corrections to initialize CE structure, and subsequent forecasts demonstrate the ability to capture the correct structural and intensity changes associated with the ERC consistently throughout the cycling. The simultaneous assimilation of GBR and TDR observations show the potential to complement each other when the vertical distributions of the observations differ. The importance of correct initialized structure is highlighted by showing that the changes in the primary and secondary eyewall throughout the forecast are consistent with balanced and unbalanced dynamics in an axisymmetric framework. Propper initialization of the secondary eyewall governs the evolution of the ERC by restricting high angular momentum air from reaching the primary eyewall, acting to contract and intensify the secondary eyewall and spin down the primary eyewall.