Tropical Cyclone Batsirai Drops Heavy Rain on La Reunion

Tropical Cyclone Batsirai dropped heavy rain on La Reunion on Thursday morning. At 10:00 a.m. EST on Thursday the center of Tropical Cyclone Batsirai was located at latitude 19.2°S and longitude 54.6°E which put it about 95 miles (150 km) north-northwest of St. Denis, La Reunion. Batsirai was moving toward the west-southwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 160 m.p.h. (260 km/h). The minimum surface pressure was 942 mb.

Tropical Cyclone Batsirai dropped very heavy rain over La Reunion on Thursday morning. A weather station at La Nouvelle reported 516.7 mm (20.34 inches) of rain. Batsirai moved slowly during the past 18 hours. The slow movement caused persistent easterly winds to blow up the eastern sides of mountains. The persistent rising motion produced very heavy rain on the eastern slopes. The very heavy rain was likely causing widespread flash floods. The heavy rain will continue until Tropical Cyclone Batsirai moves farther away from La Reunion.

Tropical Cyclone Batsirai appeared to have concentric eyewalls based on radar images from La Reunion and on satellite images. A small inner eye and eyewall was present inside a larger outer eyewall. The inner eyewall was weakening, but it was still visible on radar and satellite images. Eventually, the inner eyewall will dissipate and the strongest winds will occur in the outer eyewall. Bands of showers and thunderstorms were revolving around the core of Batsirai’s circulation. Storms near the core generated upper level divergence that pumped mass away from the tropical cyclone.

The circulation around Tropical Cyclone Batsirai contracted slightly. Winds to hurricane/typhoon force extended out 40 miles (65 km) from the center of Batsirai. Winds to tropical storm force extended out 175 miles (280 km) from the center of circulation. The Hurricane Intensity Index (HII) for Tropical Cyclone Batsirai was 25.1. The Hurricane Size Index (HSI) was 14.4 and the Hurricane Wind Intensity Size Index (HWISI) was 39.5.

Tropical Cyclone Batsirai will move through an environment capable of supporting a strong tropical cyclone during the next 48 hours. Batsirai will move over water where the Sea Surface Temperatures are near 29˚C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Tropical Cyclone Batsirai is likely to weaken during the next few hours while it completes the eyewall replacement cycle. Batsirai could strengthen again after it completes the eyewall replacement cycle.

Tropical Cyclone Batsirai will move north of a high pressure system over the Southwest Indian Ocean. The high pressure system will steer Batsirai toward the west-southwest during the next several days. Tropical Cyclone Batsirai will continue to bring gusty winds and locally heavy rain to La Reunion during the next 12 hours. The heaviest rain will continue to fall on the eastern slopes of mountains where the winds were blowing up the slopes. Continued heavy rain could cause devastating flash floods in some locations. Weather conditions on La Reunion will improve gradually when Batsirai moves farther away. On its anticipated track Tropical Cyclone Batsirai could reach the east coast of Madagascar south of Toamasina in 48 hours. Batsirai is likely to be the equivalent of a major hurricane when it reaches Madagascar.