Tropical Cyclone Chalane formed over the South Indian Ocean northeast of La Reunion on Thursday. At 7:00 a.m. EST on Thursday the center of Tropical Cyclone Chalane was located at latitude 15.4°S and longitude 58.2°E which put it about 410 miles (665 km) north-northeast of La Reunion. Chalane was moving toward the west at 12 m.p.h. (19 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 996 mb.
The circulation around a low pressure system northeast of La Reunion strengthened on Thursday and the system was designated at Tropical Cyclone Chalane. The circulation around Chalane was still organizing. The distribution of thunderstorms around Tropical Cyclone Chalane was asymmetrical. The strongest thunderstorms were occurring in bands southeast of the center of circulation. The strongest winds were occurring in those rainbands. Bands in other parts of Chalane consisted primarily of showers and lower clouds. Storms southeast of the center of circulation generated upper level divergence which pumped mass away to the south of the tropical cyclone.
Tropical Cyclone Chalane will move through an environment favorable for intensification during the next 36 hours. Chalane will move over water where the Sea Surface Temperature is near 28°C. It will move under the western end of an upper level ridge over the South Indian Ocean. The ridge will produce northerly winds which will blow toward the top of the tropical cyclone. Those winds will cause moderate vertical wind shear and they will inhibit intensification during the next 12 hours. Chalane will move into an area where the upper level winds will be weaker on Friday and it could strengthen more.
Tropical Cyclone Chalane will move south of a high pressure system over the South Indian Ocean. The high will steer Chalane toward the west during the next several days. On its anticipated track Tropical Cyclone Chalane will pass north of Mauritius and La Reunion. Chalane could approach northern Madagascar in about 48 hours. Tropical Cyclone Chalane will bring gusty winds and locally heavy rain to parts of northern Madagascar. Heavy rain could cause flash floods in some locations.