A new operational convection-permitting NWP system for tropical cyclone forecasting in the SW Indian Ocean

The sub-division of Météo-France in La Réunion Island is formally designated as Regional Specialized Meteorological Centre (RSMC) for the provision of forecasts and warnings of hurricanes in the south-west Indian Ocean (SWIO). In this regard, the French Weather Service is currently deploying a new, convection-permitting, numerical weather prediction (NWP) system to provide high resolution forecasts of tropical disturbances developing in its area of responsibility. This model, referred to as Arome-IO, will cover a domain of approximately 3000 km x 1500 km over 90 vertical levels at the horizontal resolution of 2.5 km. It will be equipped with a 3D-VAR mesoscale assimilation scheme allowing for the assimilation of high space-time resolution observations such as radar (reflectivity and radial winds), GPS and new satellite data, available within the model-covered area. After a brief overview of the model specifications, this study will evaluate the benefit of using simulations with explicit convection for tropical cyclone prediction in the SWIO basin. Arome-IO simulations of tropical cyclones Dumilé (TC07S) and Felleng (TC13S), which both passed nearby La Réunion Island in early 2013, will be compared against available observations, low-resolution operational model forecasts and high-resolution research model outputs. These two tropical cyclones produced strong winds and intense precipitation over la Réunion, Maurice and Madagascar (with up to 800 mm of rain in 24-h over La Réunion) and both presented a period of rapid intensification.