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

Abstract

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.

Landslide Processes Involved in Volcano Dismantling From Past to Present: The Remarkable Open‐Air Laboratory of the Cirque de Salazie (Reunion Island)

“…The island is regularly hit by tropical cyclones (TCs), which develop over the southwest Indian Ocean (approximately 10 TCs form in this region every year, cf., http://www.meteofrance.re/cyclone/saisons-passees). The strong orographic effect of the island influences the intensity and track of cyclones, which are apt to trigger heavy rainfall (Barbary et al., 2019; Pohl et al., 2016). As a result, Reunion Island holds world records for amounts of intense rainfall (e.g., 1,825 mm in 24 hr during TC Denise in 1966, 5,678 mm in 10 days and 6,083 mm in 15 days during TC Hyacinthe in 1980) (Barcelo et al., 1997; Chaggar, 1984; Quetelard et al., 2009).…”

Impact of Tropical Cyclones on Inhabited Areas of the SWIO Basin at Present and Future Horizons. Part 1: Overview and Observing Component of the Research Project RENOVRISK-CYCLONE

“…ESPOIRS also includes an ambitious local component aimed at collecting wind and precipitation measurements in tropical cyclones with a transportable polarimetric weather radar to be deployed in Réunion Island (2021), the Seychelles (Mahe, 2022), and Madagascar (Tamatave or Diego Suarez, 2023). This weather radar component will notably focus on the impact of orography on tropical cyclones (or outer cyclonic rainbands in the Seychelles) [130], and will help to develop regional cooperation in the field of atmospheric remote sensing.…”

Track Deflection of Typhoon Maria (2018) during a Westbound Passage Offshore of Northern Taiwan: Topographic Influence

“…This study discusses several important aspects of the track deflection associated with an approaching TC near offshore of a mountain range. A modified form of nondimensional number (R/Ly), where R is the radius of RMW and Ly is the length scale of the mountain in the direction normal to the TC movement, has been proposed by a prior study to explain the track deflection of TCs past and around Réunion Island (Barbary et al 2019). As mentioned in the Introduction, this non-dimensional number, however, is better suited for TCs impinging upon the major part of a mountain with appreciable upstream blocking (Huang and Lin 2008;Lin et al 2005;Huang et al 2016).…”

“…It has not been rare to observe large track variations of tropical cyclones translating past an isolated high mountain or a mountain range over 3000-m height, such as the Central Mountain Range (CMR) in Taiwan Island over the western North Pacific (WNP), Réunion Island over the Indian Ocean east of Madagascar, and Hawai'i's Big Island (e.g., Chambers and Li 2011;Hsu et al 2018;Barbary et al 2019). Tropical cyclones moving past an isolated mountain range like the CMR have been widely investigated using observations and numerical models, and more recently with great attention to the track deflection prior to and after landfall at the mountain (e.g., Jian and Wu 2008;Lin and Savage 2011;Huang et al 2011;Chien and Kuo 2011;Hsu et al 2013Hsu et al , 2018Wu et al 2015;Tang and Chan 2016a,b;Huang et al 2016Huang et al , 2019Huang et al , 2020Lin et al 2016;Huang and Wu 2018).…”