A low formed southwest of Sumatra and moved to the southeast reaching cyclone intensity overnight from 5-6 May. Billy then adopted a southerly then southwesterly course as it intensified briefly crossing west of 90°E on 9 May and being renamed Lila by Mauritius Meteorological Service. Billy re-entered the western region as it peaked in intensity at 95 knots before gradually weakening owing to increasing wind shear as it accelerated to the southeast.
The low crossed the Western Australian coast at Geraldton and rainfall of up to 70 mm fell across the Southwest Land Division bringing valuable opening rains to the agricultural sector.Tropical cyclone Billy was the last cyclone in the Western region of the 1985-86 season and occurred outside the normally accepted cyclone period.
For more details see the TC Billy Report (pdf)
Track and intensity
All times in WST - subtract 8 hours to convert to UTC.