Presented on October 22, 2025, by

Prof. Shu-Hua Chen
College of Agricultural and Environmental Sciences
UC Davis

ABSTRACT:

In September 2022, NASA conducted the Convective Processes Experiment-Cabo Verde (CPEX-CV) campaign over the data-sparse eastern Atlantic. Over this region, CPEX-CV collected a suite of dense observations to aid in the study of convective systems. Tropical Storm (TS) Hermine formed in late September and was the only tropical cyclone that occurred within flight range during the CPEX-CV campaign. Hermine had an unusual northward trajectory and interacted with a dust-rich Saharan air layer (SAL) to its west. Hermine was sampled by two consecutive research flights prior to becoming a TS, which provided an opportunity to improve Hermine’s forecast via data assimilation and verify model forecasts. Two experiments were conducted. One experiment assimilated CPEX-CV observations (WCPEX) while the other did not (WoCPEX). Compared to WoCPEX, the assimilation of CPEX-CV observations in the WCPEX analysis produced a stronger SAL, more intense dry-air intrusion, more easterly wind bias corrections, and a stronger mid-level circulation within pre-Hermine. Forecasts show that the strengthening of pre-Hermine into a TS in WoCPEX was delayed by 12 hours due to the large vertical tilt of the vortex and weak mid-level vorticity; it also had a westward track bias. Compared to WoCPEX, WCPEX shows that, while convection near pre-Hermine was weaker at early forecast times due to a more intense dry-air intrusion, stronger, more organized mid-level vorticity, and better vertical alignment of the vortex improved the intensity and track forecast.