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Thursday 20 July 2000

Flood rains, damaging winds, tornadoes and storms in Tas, SA 9Aug00
The second sharp upper trough and frontal system to move across in as many days brought snow, gales and flooding rain to northern Tasmania, and gales and storms to SA today and overnight into Friday. The synoptic situation was unusual. A front which moved rapidly east to lie along the SA and western Tasmanian coasts at 10 this morning suddenly slowed to a crawl, taking another 12 hours to move the 300km length of the north Tasmanian coast, and progressing only slowly into western Victoria. In Tasmania, heavy rain with some thunderstorms occurred in the strong moist northwesterlies ahead of the front, helped by sea-surface temperatures up to 3 above normal in western Bass Strait, and prolonged by the front's slow movement. During the evening, a faster-moving sharp upper trough with temperatures at 18,000 feet down to minus 30 interacted with the surface front, generating stronger uplift, a sharp surface trough, thunderstorms and squally winds which moved over southeastern SA, western Victoria and gave renewed though brief heavy falls in northern Tasmania.
Rain for the 24 hours to 9am Friday, though most fell during the day and evening of Thursday

Northern Tasmania bore the brunt of the weather, with downed trees, flooding in most northern rivers, highland snow and coastal gales all making news. In Devonport, a caravan caught fire after a tree was blown on to it, injuring a woman, while a fisherman is presumed lost after the wreckage of his boat was blown ashore on Low Head, north of Launceston, in 90km/h winds. Uprooted trees and torn branches combined with widespread flooding to make road travel difficult across the state's north. Police reported 25 roads and highways blocked, including the main Tasman Highway and the East and West Tamar Highways.

The heaviest rain fell in the northeast highlands, where the Beauty Flat Road gauge, 15km north of Fingal, recorded 123.4mm for the 24 hours to 9am Friday. Major flooding resulted late today and Friday in the middle and lower reaches of the North Esk River, with a peak of 3.2m at 6am Friday at Corra Linn, 10km SE of Launceston. Minor flooding occurred in the South Esk, Meander, Mersey and Forth Rivers, while flash flooding was reported in both the northeast and northwest from heavy showers and thunderstorms. Rainfall totals of between 50 and 100mm were recorded across the whole North Coast for the 24 hours to 9am Friday, while in the 3 days ended the same time, the Wildlife Nursery at Quamby Bluff south of Deloraine recorded 159.2mm, Diddleum, 30km NE of Launceston, reported 145.8 and Frankford, halfway between Launceston and Devonport, 133.2mm. Launceston Airport recorded its wettest July day on record, as did several other centres. Details are in the rainfall boxes for 21 June 2000. Several centimetres of snow fell across the Western Tiers and Central Plateau down to about the 800m level overnight into Friday, and Ben Lomond ski resort, 50km ESE of Launceston, received about 20cm of snow, kicking off the relatively short and variable Tasmanian ski season. Unfortunately, once again, the parched southeast missed most of the rain, though some useful falls were recorded in the Midlands.

In southeastern South Australia, squall lines associated with the developing surface trough gave wind gusts over 100km/h to many coastal places (see box below), bringing down trees, branches and powerlines, and causing brief heavy rain. Roads were blocked, power blacked out and a spate of traffic accidents resulted. Tornadoes tore through Woodchester, 45km SE of Adelaide, and Hatherleigh and Cape Jaffa, 45 and 140km northwest of Mount Gambier respectively. The most severe, at Hatherleigh, left a footprint 5km long by 100m wide along which winds to 200km/h were estimated by the Bureau of Meteorology, making the tornado a weak F2 category. Field bins were blown up to 1km, a large shed blown apart, and forests of pine trees snapped in half.

Today's highest rainfall totals for the 24 hours to 9am

60.0 Thredbo Village NSW
35.8 Frenchman Bay WA
33.2 Koetong Vic
33.0 Hunters Hill Vic

High falls for other periods:

South Australia:
Mt Gambier AP
: 18mm in 3h to 9am and 17mm in 3h to 9pm

Tasmania:
Marrawah: 37mm in 9h to 6pm
Smithton AP: 46mm in 6h to 3pm, 65mm in 12h to 9pm
Wynyard AP: 46mm in 6h to 3pm
Burnie: 43mm in 6h to 3pm
Sheffield: 13mm in 2h to 11pm
Devonport AP: 18mm in 3h to midnight tonight
Liawenee: 25mm in 6h to 3pm

 

Today's highest & lowest temps

Other extremes

Wind gusts, SA:
Neptune Is:
117km/h at 5.58pm with 10 min average of 91km/h
Cape Willoughby, Kangaroo Is: 100km/h at 7.07pm
Kuitpo: 85km/h at 8.30pm and 10.34pm
Mt Lofty summit: 119km/h at 9.43pm with 10 min average of 76km/h
Parawa: 93km/h at 7.44pm
Strathalbyn: 98km/h at 8.38pm with 10 min average of 80km/h
Cape Jaffa: 111km/h at 8.13pm and 8.21pm

Wind gusts, Vic:
Dunns Hill, Mt Dandenong: 89km/h at 7.30pm
Rhyll, Philip Island: 91km/h at 9.30pm
Lookout Hill: 93km/h at 10pm
Aireys Inlet: 89km/h at 8.30pm
Dartmoor: 89km/h at 8.55pm

Wind gusts, Tas:
Cape Grim: 93km/h at 10.00am
Devonport AP: 89km/h at 11.39am
Mt Wellington summit: 113km/h at 9.30am and 9.39am with 10 min average of 91km/h at 10.00am
King Is AP: 104km/h at 7.54pm

Records set this day

.

Maximum Minimum
34.7 Bidyadanga Broome WA 23.0 McCluer Is NT
-3.0 Crackenback NSW -6.0 Crackenback NSW

Greatest variations from normal

Maximum Minimum
+7.5
27.0 Alice Springs AP NT
+5.8
15.4 Jurien WA
-4.0
26.1 Gudgerama Maningrida NT
-7.3
10.8 Cooktown AF Qld