Observations and High-Resolution Numerical Simulations of a Non-Developing Tropical Disturbance in the Western North Pacific
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Uncertainty still remains in determining whether a tropical cloud cluster will eventually develop into a tropical cyclone. During T-PARCTCS-08, a tropical disturbance TCS025 was closely observed for potential formation during five aircraft reconnaissance missions. However, similar to the outcome for the majority of such systems, TCS025 failed to intensify. This provided for an unprecedented dataset of a non-developing system, which included airborne ELDORA dual Doppler radar. An in-depth examination of observations revealed that TCS025 failed to develop due to vertical wind shear and misalignment of the circulation structure in the vertical. Poor vertical alignment kept the circulation exposed to negative environmental influences that impacted the inner-core thermodynamic structure. This weakened subsequent convection that might otherwise have improved alignment and contributed to development. A multi-physics ensemble using the WRF-ARW model was employed to expand upon the observational findings. Simulations that developed TCS025 exhibited exaggerated convective precipitation processes and improved circulation alignment. Data assimilation experiments that incorporated aircraft and radar data provided improved initial conditions to examine the impact of a weak, misaligned circulation. Although convective precipitation processes were still over-represented, development of TCS025 was delayed, which allowed environmental factors to more severely impact TCS025 and limit its development.
- Numerical Mathematics