Cyclone Inigo - Meteorological History

Meteorological History

By 26 March, an area of disturbed weather was located within the near-equatorial trough near Papua New Guinea. Initially located within an area of easterly wind shear, it tracked westward due to the presence of a ridge to its south, and on 27 March a low pressure area formed over Western New Guinea. Thunderstorm activity increased around a mid-level circulation as it crossed into the Arafura Sea, and its overall organization continued to increase. On 29 March, a low-level circulation was visible, though significant tropical development was prevented due to wind shear and land interaction with islands in the Indonesian archipelago. It developed into a tropical low on 30 March, and after turning to the southwest, it crossed the island of Flores on 31 March; upon doing so its convection greatly increased due to increased upper-level divergence, which produced heavy rainfall on Flores and Timor. On 1 April, wind shear decreased as it crossed into the Savu Sea, and by early on 1 April it developed into a tropical cyclone to the northeast of Sumba.

At 1200 UTC on 1 April, the Joint Typhoon Warning Center (JTWC) issued its first advisory on the system, classifying it as Tropical Cyclone 26S. At 0000 UTC on 2 April, the Bureau of Meteorology (BOM) warning center in Perth classified the low as Tropical Cyclone Inigo. The storm quickly intensified as it tracked southwestward, aided by low wind shear and strong divergence. An eye featured gradually organized, and early on 3 April the BOM classified Inigo as a severe tropical cyclone with winds of 80 mph (130 km/h). Later that day, the cyclone underwent rapid intensification as the eye became increasingly better defined. On 4 April, Inigo attained Category 5 status on the Australian cyclone scale, and at 0600 UTC it reached peak winds of 240 km/h (150 mph) and an estimated minimum pressure of 900 hPa (mbar) while located about 950 km (590 mi) north of Onslow, Western Australia. Around the same time, the JTWC assessed Inigo as a powerful cyclone with 1-min winds of 260 km/h (160 mph). With a minimum pressure of 900 hPa, Inigo tied Cyclone Gwenda of the 1998-99 season as the most intense tropical cyclone on record in the Australian cyclone region.

Upon reaching peak intensity, Inigo maintained an eyewall 32 km (20 mi) in diameter. Late on 4 April, an approaching upper-level trough increased wind shear over the system, which caused a steady weakening trend. On 5 April, the eye became cloud-filled, and later that day the cyclone reached its westernmost point before the approaching trough turned it to the southeast. By 7 April, its winds decreased to below severe tropical cyclone status, or below 120 km/h (75 mph). The convection continued to decrease, leaving the center exposed from the convection as it made landfall early on 8 April in the Pilbara region of Western Australia. Upon moving ashore, Inigo had winds of around 75 km/h (45 mph), and the circulation dissipated within 12 hours after moving ashore.