BILLY-LILA
1985-86 season · AU198586_14U
History
Severe Tropical Cyclone Billy-Lila was an unusual late-season system that developed from a weak monsoonal low southwest of Sumatra on 4 May 1986, forming outside the typical Australian cyclone season window. The system organised over warm tropical waters and was named Billy by the Bureau of Meteorology after reaching tropical cyclone intensity on 5–6 May. Tracking southwestward, it crossed the 90°E meridian on 9 May and entered the Southwest Indian Ocean basin, where the Mauritius Meteorological Service renamed it Lila. An atmospheric trough subsequently drew the storm back eastward, and it re-crossed 90°E on 10 May, reverting to the name Billy under Australian jurisdiction.
Shortly after re-entering the Australian area of responsibility, Billy reached its peak intensity as a Category 4 severe tropical cyclone, with a minimum central pressure of 950 hPa and sustained 10-minute winds of 175 km/h. The system then accelerated southeastward into unfavourable conditions, rapidly weakening as it encountered strong wind shear and cooler waters. It fell below cyclone intensity just prior to its remnant circulation crossing the Western Australian coast near Geraldton on 14 May 1986, before fully dissipating over the Great Australian Bight on 15 May. Because the system had already weakened to a post-tropical low at landfall, it caused no structural damage or casualties. The widespread tropical moisture it delivered to the region produced up to 70 mm of rainfall, providing beneficial unseasonal opening rains for the local agricultural sector.
Sources: Bureau of Meteorology report Wikipedia
View full track data (47 observations)
| Date/Time (UTC) | Category | Position | Pressure | Wind |
|---|---|---|---|---|
| 1986-05-04 18:00:00 | 1 | -4.7, 89.3 | 1002 hPa | 10 km/h |
| 1986-05-05 00:00:00 | 1 | -4.8, 90.2 | 1001 hPa | 13 km/h |
| 1986-05-05 06:00:00 | 1 | -5.0, 91.2 | 1000 hPa | 13 km/h |
| 1986-05-05 12:00:00 | 1 | -5.5, 91.8 | 999 hPa | 13 km/h |
| 1986-05-05 18:00:00 | 1 | -6.1, 92.2 | 997 hPa | 15 km/h |
| 1986-05-06 00:00:00 | 1 | -6.5, 92.3 | 993 hPa | 18 km/h |
| 1986-05-06 06:00:00 | 1 | -7.1, 92.4 | 990 hPa | 21 km/h |
| 1986-05-06 12:00:00 | 1 | -7.5, 92.7 | 990 hPa | 21 km/h |
| 1986-05-06 18:00:00 | 1 | -7.8, 92.8 | 990 hPa | 21 km/h |
| 1986-05-07 00:00:00 | 1 | -8.1, 93.1 | 988 hPa | 23 km/h |
| 1986-05-07 06:00:00 | 1 | -8.5, 93.4 | 985 hPa | 26 km/h |
| 1986-05-07 12:00:00 | 1 | -8.7, 93.5 | 984 hPa | 26 km/h |
| 1986-05-07 18:00:00 | 1 | -9.3, 93.6 | 982 hPa | 28 km/h |
| 1986-05-08 00:00:00 | 1 | -9.7, 93.4 | 980 hPa | 31 km/h |
| 1986-05-08 03:00:00 | 1 | -9.9, 93.2 | 979 hPa | 31 km/h |
| 1986-05-08 06:00:00 | 1 | -10.1, 92.9 | 978 hPa | 33 km/h |
| 1986-05-08 09:00:00 | 1 | -10.4, 92.8 | 977 hPa | 33 km/h |
| 1986-05-08 12:00:00 | 1 | -10.9, 92.7 | 976 hPa | 33 km/h |
| 1986-05-08 16:00:00 | 1 | -11.4, 92.4 | 968 hPa | 39 km/h |
| 1986-05-08 18:00:00 | 1 | -11.6, 92.3 | 960 hPa | 41 km/h |
| 1986-05-08 21:00:00 | 1 | -11.9, 91.9 | 960 hPa | 41 km/h |
| 1986-05-09 00:00:00 | 1 | -12.3, 91.8 | 960 hPa | 41 km/h |
| 1986-05-09 06:00:00 | 1 | -13.0, 91.1 | 960 hPa | 41 km/h |
| 1986-05-09 12:00:00 | 1 | -13.7, 90.3 | 960 hPa | 41 km/h |
| 1986-05-09 18:00:00 | 1 | -14.4, 89.7 | 960 hPa | 41 km/h |
| 1986-05-10 00:00:00 | 1 | -15.0, 89.5 | 959 hPa | 44 km/h |
| 1986-05-10 06:00:00 | 1 | -15.9, 89.6 | 958 hPa | 44 km/h |
| 1986-05-10 12:00:00 | 1 | -16.8, 89.7 | 954 hPa | 46 km/h |
| 1986-05-10 18:00:00 | 1 | -17.8, 90.0 | 950 hPa | 46 km/h |
| 1986-05-11 00:00:00 | 1 | -18.6, 90.9 | 954 hPa | 46 km/h |
| 1986-05-11 06:00:00 | 1 | -19.4, 92.0 | 962 hPa | 44 km/h |
| 1986-05-11 12:00:00 | 1 | -20.1, 93.1 | 970 hPa | 36 km/h |
| 1986-05-11 18:00:00 | 1 | -20.5, 94.5 | 976 hPa | 31 km/h |
| 1986-05-12 00:00:00 | 1 | -21.7, 96.3 | 982 hPa | 26 km/h |
| 1986-05-12 06:00:00 | 1 | -22.7, 99.0 | 988 hPa | 23 km/h |
| 1986-05-12 12:00:00 | 1 | -23.4, 101.3 | 991 hPa | 21 km/h |
| 1986-05-12 18:00:00 | 1 | -25.0, 103.8 | 994 hPa | 18 km/h |
| 1986-05-13 00:00:00 | 1 | -26.1, 106.7 | 996 hPa | 15 km/h |
| 1986-05-13 06:00:00 | 1 | -27.4, 109.9 | 998 hPa | 15 km/h |
| 1986-05-13 12:00:00 | 1 | -28.3, 113.6 | 999 hPa | 13 km/h |
| 1986-05-13 18:00:00 | 3 | -29.7, 116.2 | 1000 hPa | 13 km/h |
| 1986-05-14 00:00:00 | 2 | -30.1, 118.0 | 1001 hPa | 13 km/h |
| 1986-05-14 06:00:00 | 2 | -30.7, 120.5 | 1001 hPa | 13 km/h |
| 1986-05-14 12:00:00 | 2 | -31.1, 122.9 | 1002 hPa | 13 km/h |
| 1986-05-14 18:00:00 | 2 | -31.1, 125.2 | 1002 hPa | 13 km/h |
| 1986-05-15 00:00:00 | 2 | -31.7, 130.2 | 1004 hPa | 13 km/h |
| 1986-05-15 03:00:00 | 2 | -32.0, 131.8 | 1004 hPa | 13 km/h |