ISOBEL
1973-74 season · AU197374_16U
History
Severe Tropical Cyclone Isobel was a long-lived system that spent more than a week over the south-east Indian Ocean in March 1974. It began as a tropical low embedded in an active monsoon trough over the Joseph Bonaparte Gulf and adjacent Timor Sea on 9 March. Drifting west-southwestward across warm waters, the low consolidated quickly and was named Isobel by the Bureau of Meteorology's tropical cyclone warning centre in Perth on 10 March.
A strong mid-level ridge over the Australian interior steered the cyclone on a southwestward course that kept it offshore, running roughly parallel to the Kimberley and then the Pilbara coastlines. Isobel continued to deepen and reached severe tropical cyclone status, Category 3 on the Australian scale, on 13 March. Its minimum central pressure of approximately 960 hPa was recorded while the system lay well out to sea beyond North West Cape, with maximum sustained winds of around 130–140 km/h and gusts over open water estimated to have exceeded 185 km/h.
An upper-level trough approaching south-western Australia later drew Isobel onto a south-southeasterly heading towards the Midwest coast. Cooler sea surface temperatures and strengthening vertical wind shear eroded the core during the final approach, and the cyclone crossed the coast in the Shark Bay–Kalbarri area on 16 March as a weakening Category 1–2 system. It then tracked inland over the Wheatbelt and dissipated on 17 March.
Impacts were moderate and no deaths were attributed to the cyclone. Squally gale-force winds caused localised damage at coastal settlements between Shark Bay, Kalbarri and Geraldton, unroofing buildings, bringing down power lines and destroying lighter structures. Gale and storm warnings were maintained for an extended period across the North West Shelf and nearby shipping lanes; offshore drilling rigs and commercial vessels contended with heavy seas but escaped serious damage. The decaying system's most widespread effect was rainfall, with persistent falls across the Gascoyne, Midwest and northern Wheatbelt districts flooding catchments, cutting regional roads and temporarily isolating farming communities.
Isobel was one of numerous systems during the exceptionally busy 1973–74 Australian region cyclone season.
Sources: Bureau of Meteorology report Wikipedia
View full track data (65 observations)
| Date/Time (UTC) | Category | Position | Pressure | Wind |
|---|---|---|---|---|
| 1974-03-09 01:00:00 | 1 | -12.3, 111.6 | 1003 hPa | 10 km/h |
| 1974-03-09 04:00:00 | 1 | -12.3, 111.5 | 1003 hPa | 13 km/h |
| 1974-03-09 07:00:00 | 1 | -12.4, 111.4 | 1003 hPa | 13 km/h |
| 1974-03-09 10:00:00 | 1 | -12.5, 111.2 | 1003 hPa | 13 km/h |
| 1974-03-09 13:00:00 | 1 | -12.6, 111.0 | 1003 hPa | 13 km/h |
| 1974-03-09 16:00:00 | 1 | -12.6, 110.8 | 1003 hPa | 13 km/h |
| 1974-03-09 19:00:00 | 1 | -12.7, 110.6 | 1003 hPa | 13 km/h |
| 1974-03-09 22:00:00 | 1 | -12.8, 110.5 | 1003 hPa | 13 km/h |
| 1974-03-10 01:00:00 | 1 | -13.0, 110.3 | 1003 hPa | 13 km/h |
| 1974-03-10 04:00:00 | 1 | -13.2, 110.2 | 1002 hPa | 13 km/h |
| 1974-03-10 07:00:00 | 1 | -13.3, 110.1 | 1001 hPa | 13 km/h |
| 1974-03-10 10:00:00 | 1 | -13.3, 109.9 | 1001 hPa | 13 km/h |
| 1974-03-10 13:00:00 | 1 | -13.4, 109.7 | 1000 hPa | 13 km/h |
| 1974-03-10 16:00:00 | 1 | -13.5, 109.6 | 1000 hPa | 13 km/h |
| 1974-03-10 19:00:00 | 1 | -13.6, 109.5 | 1000 hPa | 15 km/h |
| 1974-03-10 22:00:00 | 1 | -13.6, 109.4 | 1000 hPa | 15 km/h |
| 1974-03-11 01:00:00 | 1 | -13.8, 109.3 | 999 hPa | 15 km/h |
| 1974-03-11 04:00:00 | 1 | -13.9, 109.3 | 996 hPa | 21 km/h |
| 1974-03-11 07:00:00 | 1 | -14.0, 109.2 | 993 hPa | 21 km/h |
| 1974-03-11 10:00:00 | 1 | -14.2, 109.1 | 991 hPa | 23 km/h |
| 1974-03-11 13:00:00 | 1 | -14.3, 108.9 | 989 hPa | 26 km/h |
| 1974-03-11 16:00:00 | 1 | -14.4, 108.8 | 984 hPa | 28 km/h |
| 1974-03-11 19:00:00 | 1 | -14.6, 108.7 | 985 hPa | 28 km/h |
| 1974-03-11 22:00:00 | 1 | -14.7, 108.6 | 983 hPa | 28 km/h |
| 1974-03-12 01:00:00 | 1 | -14.8, 108.6 | 981 hPa | 28 km/h |
| 1974-03-12 04:00:00 | 1 | -15.2, 108.5 | 980 hPa | 31 km/h |
| 1974-03-12 07:00:00 | 1 | -15.6, 108.4 | 978 hPa | 31 km/h |
| 1974-03-12 10:00:00 | 1 | -16.1, 108.3 | 977 hPa | 33 km/h |
| 1974-03-12 13:00:00 | 1 | -16.5, 108.2 | 976 hPa | 33 km/h |
| 1974-03-12 16:00:00 | 1 | -16.8, 108.1 | 975 hPa | 33 km/h |
| 1974-03-12 19:00:00 | 1 | -17.3, 107.9 | 974 hPa | 36 km/h |
| 1974-03-12 22:00:00 | 1 | -17.6, 107.7 | 974 hPa | 36 km/h |
| 1974-03-13 01:00:00 | 1 | -18.1, 107.6 | 973 hPa | 36 km/h |
| 1974-03-13 04:00:00 | 1 | -18.6, 107.4 | 975 hPa | 36 km/h |
| 1974-03-13 07:00:00 | 1 | -19.2, 107.2 | 975 hPa | 36 km/h |
| 1974-03-13 10:00:00 | 1 | -19.6, 106.9 | 977 hPa | 33 km/h |
| 1974-03-13 13:00:00 | 1 | -20.2, 106.6 | 982 hPa | 31 km/h |
| 1974-03-13 16:00:00 | 1 | -20.4, 106.2 | 986 hPa | 28 km/h |
| 1974-03-13 19:00:00 | 1 | -20.7, 105.7 | 985 hPa | 28 km/h |
| 1974-03-13 22:00:00 | 1 | -21.0, 105.4 | 986 hPa | 28 km/h |
| 1974-03-14 01:00:00 | 1 | -21.3, 104.9 | 988 hPa | 26 km/h |
| 1974-03-14 04:00:00 | 1 | -21.6, 104.4 | 990 hPa | 26 km/h |
| 1974-03-14 07:00:00 | 1 | -21.8, 103.7 | 989 hPa | 23 km/h |
| 1974-03-14 10:00:00 | 1 | -22.2, 103.3 | 990 hPa | 23 km/h |
| 1974-03-14 13:00:00 | 1 | -22.5, 102.6 | 993 hPa | 21 km/h |
| 1974-03-14 16:00:00 | 1 | -22.8, 102.0 | 994 hPa | 21 km/h |
| 1974-03-14 19:00:00 | 1 | -23.1, 101.3 | 993 hPa | 21 km/h |
| 1974-03-14 22:00:00 | 1 | -23.4, 100.7 | 993 hPa | 21 km/h |
| 1974-03-15 01:00:00 | 1 | -23.6, 100.1 | 994 hPa | 21 km/h |
| 1974-03-15 04:00:00 | 1 | -23.7, 99.5 | 995 hPa | 21 km/h |
| 1974-03-15 07:00:00 | 1 | -23.7, 98.7 | 994 hPa | 21 km/h |
| 1974-03-15 10:00:00 | 1 | -23.6, 98.1 | 996 hPa | 18 km/h |
| 1974-03-15 13:00:00 | 1 | -23.4, 97.4 | 1000 hPa | 15 km/h |
| 1974-03-15 16:00:00 | 1 | -23.2, 96.8 | 1003 hPa | 13 km/h |
| 1974-03-15 19:00:00 | 1 | -23.0, 96.1 | 1002 hPa | 13 km/h |
| 1974-03-15 22:00:00 | 1 | -22.8, 95.5 | 1002 hPa | 13 km/h |
| 1974-03-16 01:00:00 | 1 | -22.6, 94.9 | 1003 hPa | 13 km/h |
| 1974-03-16 04:00:00 | 1 | -22.5, 94.6 | 1004 hPa | 13 km/h |
| 1974-03-16 07:00:00 | 1 | -22.3, 94.3 | 1003 hPa | 13 km/h |
| 1974-03-16 10:00:00 | 1 | -22.0, 93.8 | 1004 hPa | 13 km/h |
| 1974-03-16 13:00:00 | 1 | -21.9, 93.3 | 1005 hPa | 13 km/h |
| 1974-03-16 16:00:00 | 1 | -21.8, 92.9 | 1006 hPa | 13 km/h |
| 1974-03-16 19:00:00 | 1 | -21.7, 92.5 | 1005 hPa | 13 km/h |
| 1974-03-16 22:00:00 | 1 | -21.5, 92.1 | 1005 hPa | 13 km/h |
| 1974-03-17 01:00:00 | 1 | -21.4, 91.7 | 1006 hPa | 13 km/h |