SIGNIFICANT WEATHER - APRIL 2000

Introduction Tropical Cyclones Thunderstorms Wind Bushfires Dust Storms Flooding
Temperature Rainfall

INTRODUCTION

Four tropical cyclones affected weather over northern Australia during April. TC Tessie crossed the coast north of Townsville, causing damage, and Vaughan threatened the north Queensland tropical coast before weakening. TC Paul passed near the Cocos Islands and Rosita crossed the coast south of Broome, causing damage. The remnants of Rosita later brought flooding rains over central Australia. In contrast, several Tasmanian locations reported the driest April on record, and dust storms occurred over parts of South Australia and northwestern Victoria.

TROPICAL CYCLONES

Queensland

A tropical low in the northern Coral Sea moved toward the coast, deepened into tropical cyclone Tessie on the 2nd and crossed the coast near Bambaroo and Crystal Creek (80km north of Townsville) early on the 3rd as a Category 2 system on landfall. Winds unroofed buildings, uprooted trees, downed power lines in the area between Ingham and Ayr. The Strand suffered wave damage with several boats destroyed. Heavy rain caused landslides on Townsville's Castle Hill destroying two homes and requiring the evacuation of another 50. Considerable damage to personal property and to Townsville City infrastructure was reported. Townsville Aero reported a record April wind gust of 130kph, a record April daily rainfall total of 271.6mm and the cyclone was the main contribution to a record April monthly total of 546.2mm.

Minor to moderate flooding in the Haughton River increased to major in the lower reaches with the highest level since the start of records in 1978 being recorded at Giru.

Tropical cyclone Vaughan formed from a tropical low which was first identified near New Caledonia on the 29th March. The low tracked northwest through the Coral Sea to become tropical cyclone Vaughan early on the 4th April. The system rapidly intensified to Category 2 during the morning of the 4th and tracked westward toward the north Queensland tropical coast. TC Vaughan weakened a little during the 5th and was downgraded to a Category 1 system before re-intensifying to Category 2 early on the 6th. However by late morning on the 6th the system again rapidly weakened and was downgraded below cyclone strength during the afternoon. The remnants of TC Vaughan drifted slowly northwest and dissipated during the 7th April.

There was no evidence of any significant impact on the coast from TC Vaughan.

Western Australia

Forming well off the Pilbara coast tropical cyclone Paul was named on the 13th while located approximately 840 km to the north-north-west of Exmouth. Moving in a west-south-west direction the cyclone showed rapid intensification and severe tropical cyclone Paul reached Category 5 status during the 15th, and the lowest central pressure was estimated to be have been about 920 hPa the following day. Severe tropical cyclone Paul passed about 200 km to the south of the Cocos (Keeling) Islands during the 17th and the central pressure was estimated to be about 940 hPa. Wind gusts at Cocos were in the order of 50 km/h. TC Paul continued to weaken as the system followed a general west-south-west track across the Indian Ocean. The Perth Tropical Cyclone Warning Centre (Perth TCWC) issued the final warning for TC Paul on the 20th when the Category 1 cyclone was in the vicinity of latitude 14.7° south and longitude 94.3° east. Tropical cyclone Rosita was named on the 17th while located approximately 670 km to the north of Port Hedland. The cyclone initially moved in a south-south-west direction. TC Rosita intensified rapidly during the 19th to a severe tropical cyclone (Category 5) with an estimated central pressure of 930 hPa and wind gusts near the centre of around 290 km/h. During that day the system changed track to an easterly direction to move towards Broome. Severe tropical cyclone Rosita changed course during the evening of the 19th to move towards the east-south-east. At around 0100WST on the 20th the severe cyclone crossed the coast about 40 km to the south of Broome. Over land the cyclone began to weaken as it headed into the Great Sandy Desert and the last warning was issued by the Perth TCWC at 1300WST on the 20th when the Category 1 cyclone was about 250 km to the south-east of Broome. Combining with other moisture sources the remnants of TC Rosita brought flooding rains to central Australia.

A maximum wind gust of 154 km/h, and 163.8 mm of rain for the 24 hours to 0900WST on the 20th were recorded at Broome aerodrome. The high winds unroofed several houses, interrupted power supplies and caused widespread damage to vegetation around the town. Further south in the vicinity of Eco Beach/Cape Villaret the damage was considerably more extensive. Buildings at the Eco Beach resort complex sustained extensive structural damage. Several accommodation units were blown over and removed from the concrete foundations.

Also in the same area, at Yardoogarra Station (40 km SSW of Broome) the homestead received significant structural damage and a semi-trailer, with a stock crate attached, was pushed onto its side. About 50 to 60 km of fencing needs to be replaced around the station. Buildings around Thangoo Station homestead suffered some minor wind damage. Once-green vegetation near the coast was stripped of all leaves by the destructive winds carrying airborne salt and sand.

THUNDERSTORMS

New South Wales

On the1st, at Denman (Hunter Valley), wind gusts to 92 km/h were recorded, trees were blown down and some roofing iron removed. At Walcha (Northern Tablelands), 50mm of rain fell in 60 minutes.

On the 3rd, at Paytens Bridge (Central West Slopes), 3cm hail was reported.

On the 21st, at Ulladulla (South Coast), 4cm hail was reported.

Victoria

On the 5th, Heavy rain leading to flash flooding occurred in the Melbourne Metropolitan area particularly in the southeast.

On the 20th, a water spout sighted off Coal Point (near Inverloch)

Tasmania

Early on the 16th, thunderstorms caused damage to houses, trees and power supplies in the north of the State, particularly around Ulverstone where one roof was carried about 500 metres.

South Australia

On the 9th, an in-feed of tropical moisture from the northeast associated with a middle layer trough caused thunderstorms to develop on and west of the Flinders and Mount Lofty Ranges during the afternoon. Heavy showers caused flash flooding in the Lower North, Mount Lofty Ranges and the Adelaide Plains. Houses were flooded and roads closed in the Lower North townships of Gladstone, Crystal Brook and Port Pirie. Gulnare, also in the Lower North, received 63mm of rain in 24 hours, breaking the daily rainfall record set in 1905. Lightning struck two trees in the eastern suburbs of Adelaide causing minor scrub fires.

Further thunderstorms on the 11th, in the north of the State, caused more flooding and road closures. A four-wheel drive vehicle was swept away by flood waters at Farina, south of Marree, when a creek burst its banks.

Western Australia

During the 20th, parts of the Lower West experienced isolated storms as a surface trough interacted with a middle level low. The highest daily totals occurred in the vicinity of the Perth metropolitan area at Jandakot (45 mm) and Swan View (42 mm). Localised flash flooding developed when Jandakot registered 38 mm of rain in the 90 minutes to 0900WST.

Northern Territory

On the 12th, a long-lived thunderstorm squall line moved across the northwestern Top End and produced winds gusts of 94 km/h at Lee Point, 10 km north of Darwin and 83 km/h at Charles Point, 25 km west of Darwin. Minor tree damage was reported in Tiwi (a northern suburb of Darwin) and a fisheries research vessel was swamped by waves during the storm and sank while being loaded on Melville Island. Strong wind gusts associated with thunderstorms were also reported on the 12th at McCluer Island (85 km/h) about 250 km northeast of Darwin and Elcho Island (estimated between 75 and 110 km/h) about 120 km west of Nhulunbuy.

WIND

Tasmania

Gales on the night of 29th/30th disrupted power supplies in various parts of the State. Gusts exceeding 90 km/h were reported at Barren Tier on the 30th; at Cape Grim on 21st & 30th; at Derwent Estuary TERS site on 16th, 20th & 30th; at Launceston Airport on 16th; and on Mt. Wellington on 3rd, 16th, 17th, 21st, 22nd & 28th.

Western Australia

The passage of a series of active cold fronts produced wind gusts of more than 90 km/h near the west coast on the 27th and 28th. Notable registrations included: on the 27th Ocean Reef (91 km/h); and on the 28th Cape Leeuwin (96 km/h), Cape Naturaliste (93 km/h) and Rottnest Island (91 km/h).

BUSHFIRES

Tasmania

On the 29th, bushfires occurred near Mayfield in the north and near Neika and Glenorchy in the south, but no serious damage was reported.

DUST STORMS

Victoria

On afternoon of 29th, dust storms were reported in the Southern Mallee/Northern Wimmera districts. Visibility was reduced to 600metres at Warracknabeal.

South Australia

On the 29th strong north to northwest winds brought dust storms to much of the agricultural areas of the State. A frontal system with rain and showers, later in the day, settled the dust and caused minor localised flooding.

FLOODING

Queensland

At the beginning of April, tropical cyclone Tessi crossed the north tropical coast followed a week later by tropical cyclone Vaughan, which had been downgraded to a tropical low by the time it crossed the coast. Only three river basins were affected by the resultant rain. Further rain during the month resulted in a total of 53 warnings being issued for four river basins, although a number of these warnings were preliminary warnings for coastal rivers and streams along the north tropical.

Haughton River:
Widespread heavy rainfall on 3rd April following ex tropical cyclone Tessi, caused rapid river rises throughout the Haughton River catchment. Minor to moderate flooding occurred in the upstream reaches, with river levels downstream at Giru reaching 2.85 metres on 4th April causing major flooding. This was the highest level since the start of records in 1978. The flood warning was finalised for the Haughton River on the 4th April when all river levels had fallen below the minor flood level.

Tully River:
Ex tropical cyclone Vaughan resulted in heavy rain in the Tully River catchment on the 7th and 8th April. River rises in the Tully River at Euramo peaked just above the level of the Bruce Highway on the 9th April causing moderate flooding. The flood warning for Tully River was finalised on the 11th April when flood levels at Euramo had fallen to near the minor flood level. Heavy rainfall on the 25th to the 26th April caused renewed rises in the Tully River. Minor flooding occurred at Euramo, but river levels remained below the approaches to the Bruce Highway. Flood warnings were issued from the 25th to 29th April.

Johnstone River:
Very heavy rainfall in the early morning of the 8th April resulted in rapid river rises in the north and south Johnstone Rivers. River levels at Innisfail reached the moderate flood level by 8am on the 8th April and fell below the minor flood level by mid afternoon.

Bulloo River:
Moderate flooding occurred in the lower Bulloo River in the Autumnvale to Thargomindah area from the 16th to 23rd April. River levels started to rise 11th to 13th April, with the first flood warning issued on the 16th April when the moderate flood level was reached. River levels reached the peak level at Thargomindah on the 18th April and the warning was finalised on the 23rd April when flood levels in Thargomindah started to ease.

Northern Territory

Widespread rains in the western parts of the Alice Springs district caused flooding in the area. Todd River peaked 3.2m at Anzac Oval on the 21st, 2.0m above flood level. About 100 people from low lying areas were evacuated to high grounds as a precautionary measure. Stuart Highway was closed for brief periods at several places including Heveitree Gap in the McDonald ranges, through which all road and rail transport passes.

TEMPERATURE

RAINFALL

Note: Some statistical records mentioned in this report are based on data that have yet to be fully validated.