Intense Tropical Cyclone Bella was a destructive tropical cyclone that passed near the Mauritiusouter island of Rodrigues. The second named storm of the season, Bella originated in the middle of January 1991 from a surge in the monsoon trough to the southwest of Sumatra. For several days, the system remained weak as it moved generally west-southwestward. On January25, it intensified to tropical storm status, but Bella took three more days to intensify to tropical cyclone status, with 10minute maximum sustained winds of 120kilometres per hour (75miles per hour). The cyclone attained peak intensity on January29, officially reaching winds of 155km/h (95mph). The Joint Typhoon Warning Center unofficially estimated winds of 240km/h (150mph), the highest the agency estimated for any storm in the Southern Hemisphere in the year. Bella later turned to the southeast and weakened, passing about 50km (30mi) west of Rodrigues on January31. The storm turned to the south-southwest and back to the southeast again, becoming extratropical on February4.
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While passing near Rodrigues, Bella produced strong winds and high tides, the latter of which caused flooding in the capital Port Mathurin. The storm was considered the worst on the island in 20years. About 1,500homes were damaged or destroyed, leaving 1,000people homeless. Bella also severely damaged crops, roads, and the power grid on Rodrigues. The storm killed about half of the Rodrigues flying fox, a critically endangered species. Elsewhere, Bella was believed to have sunk a Madagascar cargo ship, with its 36people on board.
Meteorological history
Similar to Cyclone Alison that had formed in early January 1991, a surge in the monsoon trough spawned what would become Tropical Cyclone Bella, associated with the Intertropical Convergence Zone.[1][2] On January13, the Joint Typhoon Warning Center (JTWC)[nb 1] began monitoring a system about 660km (410mi) southwest of Padang, Sumatra in the Australian basin. Moving to the west-southwest, the system crossed into the south-west Indian Ocean on January17, and the next day was tracked by the Météo France office in Réunion (MFR).[nb 2] On January20, the disturbance turned sharply to the south-southeast, although its westward motion resumed late the following day,[5] influenced by a ridge to the south.[1]
On January22, the disturbance intensified into a tropical depression.[5] The JTWC upgraded the storm to tropical storm status on January23, three days after classifying it as Tropical Cyclone 08S.[6][5] On January25, the MFR upgraded the depression to Tropical Storm Bella, a week after beginning to issue advisories. Around that time, the storm became visible on MFR satellite imagery.[5][2] Following a lengthy period of minimal development, Bella subsequently intensified at a more regular rate as it slowed its forward motion. On January26, it turned more to the southwest, but the westward track resumed on the next day.[5] Aided by warm sea surface temperatures of 28°C (82°F), Bella began to intensify quickly.[2] On January28, both the JTWC and the MFR upgraded the storm to the equivalent of a minimal hurricane, estimating winds of 120km/h (75mph); this made Bella a tropical cyclone, the first of the season.[5] Around this time, the storm developed a well-defined eye 60km (35mi) in diameter.[2]
After becoming a tropical cyclone, Bella continued to intensify, reaching peak winds on January29. The MFR estimated 10minute winds of 155km/h (95mph), and assessed a barometric pressure of 936mbar (27.6inHg) at that time. Meanwhile, the JTWC estimated 1minute peak winds of 240km/h (150mph);[5] this strength, equivalent to a super typhoon, was the highest the JTWC estimated for any Southern Hemisphere storm during the tropical cyclone year.[6] On January30, Bella turned to the southeast and began weakening,[5] affected by wind shear in the region.[1] The cyclone passed about 50km (30mi) west of Rodrigues at 03:00UTC on January31,[2] with 10minute winds of 135km/h (85mph). Shortly thereafter, the cyclone deteriorated into a tropical storm. The southeast trajectory was short-lived, as Bella turned more to the south-southwest on February1.[5] After a final turn to the southeast, Bella became an extratropical cyclone on February4.[2]
Impact and aftermath
Before Bella affected land, a class one warning, the lowest of four, was issued for Réunion, while a class four warning was issued for Rodrigues.[7]
While moving near Rodrigues, Bella produced wind gusts of 210km/h (130mph),[8] along with high tides that flooded the northern coastline, including the capital Port Mathurin.[2] The storm damaged 1,200homes and destroyed 300others,[8] leaving about 1,000people homeless.[2] About 30schools were wrecked. The storm damaged about 75% of the electrical network was damaged, which also disrupted water supply on the island, and about 30% of roads were damaged.[2] Over 90% of the crops on the island were destroyed,[2] with many livestock killed.[8] Cyclone Bella killed about half of the Rodrigues flying fox, a critically endangered species, decreasing the numbers from around 800 to around 400. The species had regrown from a minimum of around 70 in 1971, and the trend toward regrowth continued after the storm, reaching about 3,500 in 2002. The storm also affected the Rodrigues warbler.[9] The storm also injured nine people,[2] and overall, Bella was considered the worst storm on the island in 20years.[10]
A 16,570ton cargo ship traveling from Madagascar to Réunion was lost on January30 about 700km (430mi) to the south of the center of Bella. The ship likely sank due to the cyclone, with 36people on board.[2]
In the aftermath of the storm, seven people contracted Typhoid fever on Rodrigues in relation to the storm.[2] After Bella passed, the government of Mauritius noted the need for 4,500m (15,000ft) of galvanized pipes to assist in rebuilding, as well as generators.[8] The United States Agency for International Development donated $25,000 (1991USD) to Mauritius to help in the aftermath. France, the United Kingdom, and India also donated to the country.[11]
The Joint Typhoon Warning Center is a joint United States Navy– United States Air Force task force that issues tropical cyclone warnings for the region.[3]
Darwin Regional Specialised Meteorological Centre (January 1991). Darwin Tropical Diagnostic Statement(PDF) (Report). Vol.10. Bureau of Meteorology. p.1. Retrieved 2014-06-09.
Kenneth R. Knapp; Michael C. Kruk; David H. Levinson; Howard J. Diamond; Charles J. Neumann (2010). 1991 Bella (1991013S04096). The International Best Track Archive for Climate Stewardship (IBTrACS): Unifying tropical cyclone best track data (Report). Bulletin of the American Meteorological Society. Archived from the original on 2015-12-22. Retrieved 2014-06-09.
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