Multi-model high-resolution analysis of Tropical-Like Cyclone Daniel with WRF and ICON: peculiarities and sensitivity to convection schemes

Abstract. Medicane Daniel (September 2023) featured a rapid transition from a baroclinic disturbance to a compact tropical-like vortex, challenging short-range prediction. This study delivers a side-by-side, high-resolution (∼2 km) assessment of Daniel using two state of the art weather forecasting models, WRF and ICON, configured to be as comparable as possible in terms of domain, forcing and vertical discretizations. Seven numerical simulations are compared assessing also sensitivity to the convection scheme: fully explicit, deep-cumulus parameterized and independent shallow-convection options (plus ICON's grayzone setting). Analysis methods include an objective cyclone tracker that combines mean sea-level pressure and lower tropospheric geopotential structure, intensity metrics (central pressure and 10 m wind) along the track, precipitation anomalies regridded against IMERG observations (Integrated Multi-satellitE Retrievals for GPM). Tropical characteristics are examined with Hart's Cyclone Phase Space and Temporal Annular Symmetric Mean (TASM) of equivalent potential temperature and wind to distill three-dimensional, time-mean storm structure during the peak warm-core phase.

Both models reproduce Daniel’s life cycle and produce realistic tracks. Intensity of the cyclone sharply varies from simulation to simulation, with different behavior of each model at changes in convection scheme.

The study emphasizes the different responses of the two models both in reproducing such an extreme meteorological phenomenon and in the variation of the convection scheme. Practical suggestions are established depending on the case study and the resolution used.