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.
![](media/2000072120000721_rrt.gif) |
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.
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