A Dedicated Convection-Permitting Ensemble in the Operational NWP Systems at Météo-France for the Tropics

Tropical cyclones are among the most destructive meteorological phenomena, making their anticipation crucial. In order to provide ever more effective guidance to RSMC – La Réunion Tropical cyclone centre, weather numerical prediction systems at Météo-France have been improved, notably the Arome Overseas operational deterministic chain, and very recently, for operations in 2023, its ensemble prediction system called AROME-OM EPS. Indeed, taking into account the small-scale uncertainties associated with tropical cyclones is quite important especially for anticipating intensity changes.

The objective of this presented study is to develop products that would facilitate the understanding of the relationship between vertical wind shear and tropical cyclone intensity changes. An original analysis has been performed, in which the classical responses of the TC’s vortex structures to wind shear (vortex tilt, azimuthal and radial distribution of deep convection,...) are addressed from a probabilistic framework. Results will be shown for intense tropical BATSIRAI, which occurred over the South-West Indian Ocean (31 janv. - 6 feb. 2023). They will illustrate how such specific probabilistic diagnostics could be useful for the forecast of BATSIRAI.