This season was characterized by very active monsoonal periods across north-western Australia. A total of seven cyclones formed in the Perth Tropical Cyclone warning Centre area of responsibility (90 - 125°E). Four cyclones occurred off the north-west Australian coast, three of which crossed the coast,Nicholas, Rachel.
Details of each Tropical Cyclone in the northwest Australian region 1996-97
Lindsay 9-13 July 1996
Lindsay was unusual in that it formed in July in the Indian Ocean. However there had been other cyclones in the Indian Ocean during the 1996 winter, being observed in May, July and August. Lindsay was first discernible as a low level circulation on 9 July near 9°S 94°E. It tracked to the southsouthwest and intensified to briefly reach cyclone status during the evening of 10 July. Lindsay then sheared apart overnight on 10 July and slowly weakened. The remnants of Lindsay slowly moved southeast over the next couple of days before being absorbed into a broad trough area on 13 July near 15°S 95°E. There were no reports of damage to shipping or observed galeforce winds.
Melanie 29 October - 1 November 1996
An area of convection to the north of Cocos Island produced a tropical low by the morning 29 October. This low was almost stationary until overnight on 30 October when it began to move west and deepen to become a cyclone by the morning of 1 November. Melanie deepened further to a category 2 storm overnight on 1 November as it moved westwards out of Perth TCWC's area of responsibility.
Nicholas 12-16 December 1996
Nicholas was the first cyclone to form off the north-western Australian coast during the 1996/97 season. It began as a weak low within the monsoon trough near Gove on 8 December and moved west-northwest to be located near Timor during 12 December. The low then moved steadily south, reaching cyclone intensity early on 14 December between Adele and Browse Islands. It passed over Browse Island at midnight on 13 December and passed just to the east of Adele Island during the afternoon of the 14th. Nicholas was near the north-west Kimberley coast during that evening, but weakened to below cyclone strength as it continued soutward through King Sound. It passed within 50 kilometres to the west of Derby around 0900 WST 15 December, then continued south and weakened further over the inland west Kimberley during the day. The low finally dissipated as a surface circulation during the afternoon of 16 December.
Gale to storm force winds were experienced by pearling boats sheltering near the entrance to King Sound. The strongest winds at Derby occurred at midnight on 14 December when easterly winds averaging 30 knots (gusts to 41 knots) were recorded. There was no wind damage reported but heavy rain over the north Kimberley caused flooding.
Ophelia 13-19 December 1996
Ophelia formed during the first active phase of the northwest monsoon in Australian longitudes for the 96/97 cyclone season. It formed between two tropical cyclones, Nicholas (near the north Kimberley coast) and Elvina near 80°E, to the east of Christmas Island. Its track was somewhat unusual in that it moved towards the southeast for most of its lifetime. It intensified rapidly to cyclone intensity by the morning of 15 December, however its intensification was short-lived as it encountered vertical wind shear early on 17 December. The cyclone had no impact on Christmas Island or northwest Australia.
Phil 26-31 December 1996
Phil formed in the Gulf of Carpentaria on 26 December and was named by Darwin TCWC. It moved rapidly westward across the Top End during that day and temporarily weakened. It was upgraded again to cyclone intensity during 27 December in the Bonaparte Gulf and entered the WA region early on 28 December. It intensified rapidly during the day and passed close to Adele Island during the early evening. By the morning of the 29th it was experiencing vertical wind shear and its structure on satellite imagery from then onwards was poor. A ship passed close to the centre early on the morning of the 30th and experienced winds up to 50 knots. Throughout its lifetime it traveled on a westsouthwest path and remained well offshore from the WA mainland. It was downgraded to below cyclone strength during the 31st. The remnants continued to move westward reaching 13°S 90°E by 5 January 1997.
Rachel 3-8 January 1997
Rachel was the third and last cyclone to cross the WA coast this season. Rachel was named by Darwin TCWC on the morning of 3 January 1997. The cyclone moved southwest and intensified to Cat.2 by the morning of 4 January when it passed between Troughton Island and Kalumburu. Rachel then weakened as it moved across the north Kimberley during the day. By the evening it was located near Kuri Bay with central pressure estimated to be 995hPa. By the morning of the 5th it was near Cape Leveque and was moving out to sea and re-intensifying. The cyclone continued the south-west track until midday on 7 January when it abruptly changed course towards the south. The eye of the cyclone passed directly over Port Hedland at 4.30pm. The cyclone then continued to move southward, weakening as it passed over the Hamersley ranges overnight. It was down-graded to below cyclone strength at 9am 8 January when it was positioned just southeast of Wittenoom. Damage to property at Port Hedland was mostly minor. Power was lost in parts of the town and numerous trees were blown over.
The radar structure of Rachel in the period during the change of motion from southwest to south showed the intense rainfall echoes on the southern side, with only weak sporadic echoes on the northern side. The wind trace from Port Hedland showed a marked asymmetry with the winds on the southern side (associated with the intense convection) almost double those on the northern side.
The following data was recorded during cyclone Rachel:
- Maximum wind speed reported
- Bedout Island Automatic weather station (AWS): 10 minute average wind speed 69 knots (128 km/h) 6am 6 January.
- Port Hedland Airport AWS: 10 minute average wind 65 knots (119 km/h) gusting to 91 knots (169 km/h) at 3.03pm 7 January.
- Minimum pressure recorded
- Port Hedland Airport AWS: 971 hPa at 4.30pm 7 December.
- Storm Surge
- 1.25 metres at Port Hedland Harbour at 3 pm 7 January
- Yarrie: 196mm in 24 hours to 9am on 8 January.
- Wittenoom: 170mm in 24 hours to 9am on 8 January.
- Broome: 194mm in 48 hours to 9am on 7 January.
Pancho/Helinda January 20 - February 5 1997
A low formed from an area of persistent convection to the north of Cocos Islands during 17 January. By the morning of 20 January it had been named Pancho as it moved south towards Cocos Islands. It then moved southwest, intensifying rapidly to a Category 4/5 cyclone with an estimated central pressure of 925 hPa by the morning of 22 January. Pancho then stalled near 90°E, was renamed Helinda by the Mauritiaun TCWC and weakened. By 29 January Pancho/Helinda was moving from the northwest towards Cocos Islands again, however again it changed direction to the southwest and reintensified to Category 4 storm by 1 February west of 90°E before finally weakening to a tropical depression by 5 February.
Tropical Low January 25 - February 1997
A slow-moving monsoonal low produced very heavy rainfall in parts of the West Kimberley, Pilbara and Gascoyne areas during late January and early February. Broome registered a phenomenal 476.6 mm of rain in the 24 hours to 9am on the 30th, of which 415.4 mm fell in the 5 hours to 3.30 am that day. A wind gust of 96 km/h was recorded during the thunderstorms. The town suffered some localized water damage and communications were disrupted when the telephone exchange was flooded. The pearling facility at Cygnet Bay, approximately 150 kilometres to the north-north-east of Broome, registered 470 mm of rain in 4 days. numerous other localities in the affected areas recorded daily totals in excess of 100 mm and Boodarie, south-west of Port Hedland, reported 215 mm of rain on the 1st February.
Heavy rainfall across inland parts of the Pilbara and Gascoyne produced one of the highest recorded levels this century on the Ashburton River. The rain commenced at the start of February as the monsoonal low moved slowly overt he region with further falls during the following week. Mount Vernon (located approximately 170 kilometres to the south-west of Newman) reported 430 mm of rain during the event of which a daily record of 250 mm was registered on the 3rd February. Bulloo Downs (located approximately 70 kilometers south of Newman) recorded a further 69 mm of rain on the 10th February. Significant stock losses were experienced and several homesteads were flooded by the rising waters. The flood waters made the North West Coastal Highway impassable. Water flowed across the top of the bridge at Nanutarra on Friday 7th February and the nearby refueling facilities were also flooded. Onslow was isolated as the flood peak reached the coast.
Tropical Low February 19-24 1997
During February 19 a tropical low formed in the monsoonal trough about 600km northwest of Karratha. It moved to the southeast and then south, deepening to have a central pressure of about 991 hPa with a well formed low-level centre by February 22. The low was 225km northwest of Karratha at its closest points and parts of the Pilbara coast were under cyclone warning conditions. The low began moving away from the coast early on February 22 and slowly weakened.
Tropical Lows February 22 -27 1997
A tropical low developed in the Timor Sea during February 22 in a period of very strong monsoonal activity. During the next 36 hours it moved on a southeast track towards the west NT coast and then south and finally westsouthwest towards the Kimberley coast near Wyndham. The 0600 WST observation from Wyndham on 24 February reported a MSL pressure of 992.4 hPa. It then moved inland and gradually weakened, though it caused severe flooding at Oombulgurri, northwest of Wyndham. Reported rainfall totals in the north Kimberley in the 24 hours to 9am 24 February included 128mm at Kalumburu, 86.2mm at Kuri Bay, 71.2mm at Mt Elizabeth and 66mm at Wyndham. The low weakened and dissipated near derby during February 25. However during February 25 another surface low developed between Wallal and La Grange/Bidyadanga, which then tracked westsouthwest and passed just north of the Bedout Island AWS about 0500 WST on February 26. The low's wentral pressure was estimated to be 998 hPa with mean sustained wind speeds of 20/30 knots near the centre. The low continued to track to the westsouthwest and passed near Barrow Island and then just to the west of Exmouth by 0200 WST on February 27, when the central pressure had risen to about 1002 hPa.