Abstract 184

Abstract ID: 184

Monthly forecast exploratory experiment with a convection permitting model for the south-west Indian Ocean basin

Lead Author: Sylvie Malardel
Laboratoire de l’Atmosphère et des Cyclones (LACy), France (La Réunion)

Keywords: convection permitting model , subseasonal scale, scale interactions

Abstract: One of the objectives of the PISSARO (Prévision Intra-Saisonnière à Saisonnière avec AROme) project is to study the contribution of a model which resolves deep convection for the monthly forecast of extreme weather in the south-west Indian Ocean (SWIO). The idea of such an extended range system is not to focus on the detailed forecast of the convective scale. But we hope that modeling explicitly the interaction between the larger weather patterns such as the MJO and the tropical waves that have some predictability at the subseasonal scale and the resolved convective circulations may improve the subseasonal probabilistic forecast of the extreme weather events (mainly tropical cyclones and heavy tropical precipitation regimes) that is strongly influenced by the large scales in the tropics.
The convection permitting model AROME already produces operational 48h forecasts with a resolution of 1.3 km, 4 times a day over a large SWIO domain. A prototype of an ensemble of 72h AROME forecasts with 16 members at a resolution of 2.5 km has been tested in near real time during the last 3 tropical cyclone seasons and it should become fully operational in the second half of 2023. In the context of the PISSARO project, this ensemble system has been adapted for extended range forecasts on a larger Indian Ocean domain across the equator.
In this talk, we will compare the information provided by the extended range AROME ensemble and by the IFS ensemble for a few test cases of tropical cyclones and heavy rainfall events in the ITCZ and analyze the contribution of modeling explicitly the tropical convection for the extended range forecast of such devastating weather phenomena.

Hélène Vérèmes (LACy)