Tropical Aviation Turbulence Induced by the Interaction Between a Jet Stream and Deep Convection

On 18 December 2022, Hawaiian Airlines flight HA35 encountered severe turbulence without warning in a cloud-free height. We reproduced this incident using the Weather Research and Forecasting Model (WRF) at a convection-permitting resolution. We found that this case of tropical upper-level turbulence occurred primarily due to the fast-growing convective tower in the unstable layer created by gravity wave breaking. At lower altitudes, a mesoscale convective system (MCS) caused a decrease in wind speed in both upstream and downstream regions. At upper levels, a large-scale jet descended and accelerated after flowing over the top of the MCS, which acted like a barrier and produced a situation similar to a downslope windstorm due to mountain terrain. Upper-level turbulence is 2-3 km higher than the top of the MCS. The critical level above the jet and the locally self-induced critical level created the locally enhanced descending jet stream, which destabilized the flow through Kelvin-Helmholtz instabilities. The convective tower existed near the flight route and played an important role in triggering turbulence in the unstable environment through its convective gravity waves. On 18 December 2022, Hawaiian Airlines flight HA35 encountered severe turbulence without warning, resulting in injuries to some passengers and damage to the equipment. This incident requires careful investigation to broaden our understanding of aviation turbulence. A numerical model at kilometer-scale resolution was used to simulate this case and reveal the dynamics, and we successfully captured the occurrence of turbulence with the simulation. The cause of the turbulence was a previously non-highlighted mechanism. Severe turbulence was generated by a fast-growing convective tower at an unstable level. This level was caused by the interaction between the convective system that acted as a barrier and an upper-level jet. Understanding the causes and spatial distribution of turbulence can help aircraft avoid potential areas with turbulence. A regionally convection-permitting model was used to reproduce a severe turbulence encounter Deep convection acted like terrain and interacted with a jet stream, causing an upper-level windstorm downstream of the convection top Fast-growing convective tower and downslope windstorm induced turbulence at different locations of the jet stream