The orographic effect of Reunion Island on tropical cyclone track and intensity

Like Taiwan, the orography of Reunion Island may impact tropical cyclone (TC) track and intensity. A Mann-Whitney test is applied on best-track data from the Regional Specialized Meteorological Center (RSMC) La Reunion to demonstrate that this effect is detectable at less than 250 km from the island. A set of idealized experiments is carried out to investigate this effect with the French non-hydrostatic mesoscale numerical model Meso-NH at 12 and 4-km horizontal grid spacing. Results show that the island influences TC track and intensity within two radii of maximum winds, defining a distance of influence. The impact is similar to an aspiration of the vortex by the island, accompanied by vortex weakening. An asymmetry is found between TCs passing north or south of the island and can be explained by the presence of the island in the flow.