Tropical Cyclone Ilsa strengthened to the equivalent of a major hurricane over the South Indian Ocean northwest of Australia on Wednesday morning. At 11:00 a.m. EDT on Wednesday the center of Tropical Cyclone Ilsa was located at latitude 16.8°S and longitude 119.4°E which put it about 200 miles (325 km) west-northwest of Broome, Australia. Ilsa was moving toward the south-southwest at 6 m.p.h. (10 km/h). The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (230 km/h). The minimum surface pressure was 956 mb.

A Tropical Cyclone Warning was in effect for the portion of the coast of Western Australia from Bidyadanga to Port Hedland. Tropical Cyclone Watches were in effect for the portions of the coast from Broome to Bidyadanga and from Port Hedland to Whim Creek.

Tropical Cyclone Ilsa strengthened to the equivalent of a major hurricane on Wednesday morning. A small circular eye was present at the center of Ilsa’s circulation. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Tropical Cyclone Ilsa. Storms near the core generated strong upper level divergence that pumped large quantities of mass away from the tropical cyclone. The removal of large quantities of mass was causing the surface pressure to continue to decrease.

The size of the circulation around Tropical Cyclone Ilsa increased, when Ilsa strengthened. Winds to hurricane/typhoon force extended out 30 miles (50 km) from the center of Ilsa’s circulation. Winds to tropical storm force extended out 115 miles (185 km) from the center. The Hurricane Intensity Index (HII) for Tropical Cyclone Ilsa was 20.6. The Hurricane Size Index (HSI) was 11.5 and the Hurricane Wind Intensity Size Index (HWISI) was 32.1. Tropical Cyclone Ilsa was similar in size and intensity to Hurricane Sally when Sally hit South Alabama in 2020.

Tropical Cyclone Ilsa will move through an environment very favorable for intensification during the next 24 hours. Ilsa will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the axis of an upper level ridge that extends from northern Australia to the South Indian Ocean. The upper level winds are weak near the axis of the ridge and there will be little vertical wind shear. Tropical Cyclone Ilsa will continue to intensify during the next 24 hours. Ilsa could intensify rapidly at times.

Tropical Cyclone Ilsa will move around the western end of a high pressure system over western Australia. The high pressure system will steer Ilsa toward the south during the next 24 hours. Tropical Cyclone Ilsa will move toward the southeast when it reaches the western end of the high pressure system on Thursday morning. On its anticipated track, Ilsa is likely to make landfall on the coast of Western Australia between Broome and Port Hedland in 30 hours. The center of Tropical Cyclone Ilsa could make landfall near Wallal Downs. Ilsa is likely to be the equivalent of a major hurricane when it makes landfall.

Tropical Cyclone Ilsa will bring very strong winds and locally heavy rain to Western Australia near Wallal Downs. The strong winds will be capable of causing severe damage. Heavy rain could cause flash floods in some locations. Flood Watches are in effect for the West Kimberley, De Grey River, Sandy Desert, Western Desert, Warburton and Salt Lake Districts. Tropical Cyclone Ilsa could also cause a storm surge of up to 10 to 15 feet (3 to 4.5 meters) along the portion of the coast near where the center makes landfall.