A New High-Resolution Operational NWP system for Tropical Cyclone Forecasting in SW Indian Ocean

In the frame of the ‘AROME Overseas' project, the French Weather Service is currently deploying a set of five new high-resolution, limited-area, models for operational weather forecasting in French Caribbean's,French Guiana, New Caledonia, French Polynesia and Indian Ocean areas (see Figure below).

A prototype version of these new models has been evaluated for about 2 years in the South-West Indian Ocean (SWIO). This test configuration, called AROME Indian, was developed in collaboration with Regional Specialized Meteorological Centre (RSMC) La Réunion, which is formally responsible for issuing forecasts and warnings of tropical cyclones in the SWIO. The model grid covers a single domain of ~ 3500 km x 2200 km over 90 vertical levels at a fixed horizontal resolution of 2.5 km, encompassing the Mozambique Channel and most inhabited islands of the basin. It is coupled with a 1-D mixed layer ocean model and is equipped with a three-dimensional variational data assimilation scheme with 3-hour assimilation cycle.

After a general description of the AROME Overseas project, this presentation will focus on the performance of the model AROME Indian for predicting TC intensification and landfall processes in the SWIO. Model forecasts of intense tropical cyclones observed during the last two cyclonic seasons such as Hellen, Bejisa and Bansi, will be assessed and discussed. In the last part of this presentation, one will also present ongoing experimental projects aiming at increasing available observations for data assimilation and model verification purposes, in this poorly documented basin