Severe Tropical Cyclone Olivia

5 - 12 April 1996

Summary

Tropical cyclone Olivia , the last to affect the Western Australian coast in the 1995/96 season, was one of the most intense systems to have crossed the Australian coast. A low to mid-level circulation was evident over the Indonesian archipelago north of Darwin from 2 April. This circulation slowly developed and drifted south. Development was assisted by a weak low-level surge across the equator north of the low. Development continued on 4 April, but was slow due to increased high-level northeasterly winds across the circulation and weak cross-equatorial flow continued into the circulation. Olivia reached category one intensity on 5 April 1996 as it turned towards the west taking it to the north of Troughton Island. This change in direction occurred as a middle-level ridge to the south strengthened. Persistent high-level northeasterly winds continued to shear convection away from the circulation and retarded the speed of development up to 7 April.

However, the passage of an upper trough to the south on 8 April weakened these upper winds and their shearing influence and the cyclone then proceeded to develop more rapidly reaching severe (category three) intensity. This trough system also weakened the middle-level ridge south of Olivia and it turned towards the southwest. Olivia reached category four intensity on 9 April and attained its peak intensity with a central pressure of about 925 hPa at 1200UTC 9 April. Another trough system approaching from the west later on 9 April 1996 continued to erode the middle-level ridge. This steered Olivia southwards on 10 April 1996 and then rapidly towards the south-southeast and the Western Australian northwest coast as the deep north- westerly flow increased ahead of the trough system. It remained at near peak intensity until it crossed the Pilbara Coast near Mardie about 1230 UTC 10 April. Olivia continued to track to the southeast and weakened to a low during 11 April 1996 when it was north of Laverton. However, it continued to produce gale-force winds on its northeast flank even as far south as Forrest near the Great Australian Bight. The low-level circulation of Olivia moved into the Bight near Eucla on 12 April.

Track and intensity

All times in WST - subtract 8 hours to convert to UTC.

Best Track of Severe Tropical Cyclone Olivia