Australian Weather News
Thursday, 22 MAR 2001
|About Australian Weather News
brings traffic chaos to N and W of Melbourne
Light snow dusts the Alps and Snowys
Second day of record cold in southern NT
Thargomindah has its coldest March night
|A narrow rainband brought 60
to 100mm to areas from the southwest to the north of Melbourne today.
It originated from a cloudmass wrapping around the underside of the low
pressure system that crossed Victoria yesterday, and was consolidating in
eastern Bass Strait today. Both Melbourne Airport and Laverton Airport,
halfway between Melbourne and Geelong, recorded nearly 110mm between about
5am and 3pm.
Flash flooding caused mayhem to traffic from the northern to western suburbs of Melbourne. Tullamarine Freeway, linking the city to the airport, was worst hit, with up to 2 metres of water in places bringing traffic to a standstill. The Age reported that one taxi driver clocked up $146 for two Sydneysiders he picked up in the city that took 2½ hours to reach the airport. The SES received over 300 calls for help, mostly in Broadmeadows, Laverton, Tullamarine, Footscray and Keilor. Parts of the West Gate Freeway and northern ring road were flooded, and Yarra Trams and Bayside Trains both cancelled services. The Titanic Theatre Restaurant in Williamtown suffered $60,000 damage, but got invaluable publicity, when water rushed through its doors. Flooding would probably have been worse if the ground around Melbourne had not been so parched from extended drought conditions over summer.
While there has not been time for a full analysis of the causes of this event, it has a number of peculiar and interesting features. No thunder was reported, cold upper air and its attendant surface low had moved away to the east overnight, the Melbourne Airport balloon ascent at 9am showed a conditionally stable (if very moist) atmosphere with an inversion at about 3,000 metres, CAPE, a measure of available energy, was a low 32, low level vorticity was modest and upper level divergence was negative. Most of the atmospheric accompaniments one would expect with such an event were missing. So why did it happen?
The satellite animation (right) shows a nearly stationary circulation off the East Gippsland coast from early morning to mid-afternoon, with a broad tongue of deep cloud curling underneath it. The cloud is some 5 or 6° warmer in the lower levels than the mostly clear air over eastern Victoria, where a cold pool is sitting to the north of the circulation. Between 10pm last night and 7 this morning, a narrow band of moderate to heavy rain persisted through the eastern Otways, Geelong and for about 100km to the north. Geelong Airport recorded 60.6mm during this time, for a 24-hour total of 62.4mm. This is unusually heavy rain for the area -- Geelong Norlane's highest March 24-hour rainfall in 30 years' observation is 58.4mm.
Radar shows the rain area easing between 7 and 9am, but spreading over most of the area between Geelong and the Dandenongs, and northwards into central northern Victoria. Shortly after 9am, an observer in Leopold, an eastern suburb of Geelong, noted a rapid increase in temperature from 11.4 to 17.1° in about 2 minutes; Geelong Airport's recording was not so sharp, but both the temperature and dew point rose 5° between 7 and 9am while the wind turned fresh southwesterly. This warm humid southwesterly persisted at Geelong for the rest of the day.
Both Melbourne and Laverton Airports, to the ENE of Geelong, however, experienced moderate north to northeasterly winds and temperatures around 5° lower than Geelong's until between 1 and 2pm, when the temperatures rose and winds turned southwesterly. It seems clear that a local convergence zone developed around mid-morning to the east of Geelong, with warm moist air -- the "returning" tropical moisture that had fed around the southern side of the low -- feeding the zone from the southwest. Around this time, the circulation shown on the satellite loop also deforms westward, while a SW/NE blue (cold-topped) cloud band develops along the convergence line which lies approximately Laverton to Melbourne Airport to Kilmore Gap, about 100km north of Melbourne.
While rain eased off at Geelong after 7am, heavy rain did not begin at Laverton, Melbourne or Kilmore Gap until after 8am. Then the heavens opened. Melbourne Airport recorded 102.2mm between 8.40 and 2pm. Laverton AP received 96.8 between 8am and 2pm, while Kilmore Gap's period of heavy rain was from 8.30 to 4pm, yielding 80.0mm. Totals dropped off substantially away from the Laverton -- Kilmore Gap axis, though Melbourne City still managed a respectable 43.8mm between 9am and 3.30, when the rain stopped abruptly. Only a handful of rainfall stations exceeded 50mm (see National Extremes for 23 March).
The automatic weather stations at Laverton, Melbourne Airport and Kilmore Gap all show the rain stopping abruptly, around 2pm to the west of Melbourne and around 4pm to the north, as the convergence zone that supported the area of heavy rain was driven NE by strengthening southwesterlies and dissipated. As this second rain phenomenon finished, a third but relatively insignificant rain event began in the Dandenongs, with over 30mm recorded at Dunns Hill between 3 and 10pm. The cloudmass that produced this event can be seen approaching the area in the last two frames of the satellite loop above.
As a final touch to an unusual two days of weather in the southeast, powder hounds were salivating at the prospects for an early winter as a light dusting of snow was reported from the peaks of the Victorian Alps and from Perisher Valley during the day.
Central Australia continued to shiver, with daytime temperatures again just making it into the mid-teens. Curtin Springs, which set a new March record low maximum for the NT of 14.4 yesterday, only reached 14.5 today, 19.3 below the long term March average. Giles and Alice Springs were both 16 or 17 below normal. Over the border in southwestern Queensland, Thargomindah recorded its lowest March minimum in 43 years of computer records when the mercury dropped to 9.6.
weather extremes for today
|Quality control note: Data is complete, and has been visually checked by AWN for gross errors. Less obvious errors may remain. See Explanation of Extremes Pages for more information
set this day (previous record and years of computerised record shown in
Lowest minimum temperature for March:
Thargomindah PO Qld: 9.6 (10.2, 43)
Todays highest rainfall totals for the 24 hours to 9am. It includes the top 5 totals received, and/or all reported falls of 50mm or more.
114.0 DERBY AERO W Kimberley
High rainfall for periods of 6 hours or less.
Todays highest & lowest temperatures
GEORGETOWN POST OFFICE Upper Carpentaria QLD
36.6 ROEBOURNE E Pilbara WA
36.6 RICHMOND POST OFFICE Upper Carpentaria QLD
36.5 GASCOYNE JUNCTION W Gascoyne WA
36.5 JULIA CREEK POST OFFICE Gulf Country QLD
MCCLUER ISLAND Darwin-Daly NT
28.0 DUM IN MIRRIE Darwin-Daly NT
27.0 COCONUT ISLAND N Peninsula QLD
27.0 WILLIS ISLAND Islands
26.6 BLACK POINT Darwin-Daly NT
26.6 CENTRE ISLAND Roper-McArthur NT
MT HOTHAM Upper NE VIC
5.0 THREDBO (CRACKENBACK STATION) AWS Snowy Mtns NSW
5.0 FALLS CREEK Upper NE VIC
6.0 CHARLOTTE PASS (KOSCIUSKO CHALET) Snowy Mtns NSW
7.0 CABRAMURRA SMHEA AWS SW Slopes S NSW
7.0 MOUNT BULLER Upper NE VIC
THREDBO (CRACKENBACK STATION) AWS Snowy Mtns NSW
-0.5 MT HOTHAM Upper NE VIC
0.0 CHARLOTTE PASS (KOSCIUSKO CHALET) Snowy Mtns NSW
0.0 MOUNT BULLER Upper NE VIC
0.4 FALLS CREEK Upper NE VIC
Todays greatest temperature variations from normal
32.2 DOUBLE ISLAND POINT LIGHTHOUSE Brisbane/SE Coast
+4.5 30.3 ALSTONVILLE TROPICAL FRUIT RESEARCH STAT North Coast NSW
+4.5 21.8 STRATHGORDON VILLAGE W Coast TAS
+4.4 24.0 WYNYARD AIRPORT N Coast TAS
+4.2 32.1 LISMORE (CENTRE STREET) North Coast NSW
16.4 DOVER (PARKS AND WILDLIFE SERVICE OFFICE Southeast
+7.5 16.0 BUSHY PARK (BUSHY PARK ESTATES) Derwent Valley TAS
+7.5 13.0 TARRALEAH CHALET Derwent Valley TAS
+7.2 15.4 GEEVESTON(FORESTRY CEMETERY RD) Southeast TAS
+6.9 12.8 LAKE LEAKE (ELIZABETH RIVER) E Coast TAS
14.5 CURTIN SPRINGS Alice Springs NT
-16.9 17.0 GILES METEOROLOGICAL OFFICE Interior WA
-16.5 16.1 ALICE SPRINGS AIRPORT Alice Springs NT
-14.1 13.0 WANGARATTA AERO Lower NE VIC
-14.0 18.2 KULGERA Alice Springs NT
9.6 THARGOMINDAH POST OFFICE COMPARISON Far SW QLD
-10.1 4.4 EYRE Eucla WA
-9.7 5.7 BARADINE FORESTRY NW Plains E NSW
-9.2 6.7 PERTH AIRPORT Lower West WA
-9.1 0.8 TARALGA POST OFFICE Goulburn/Monaro NSW
Highest wind gusts above 89km/h or mean wind above 62km/h (gale force). Wind direction and mean windspeed shown in brackets.
ROTTNEST ISLAND Lower West WA
: 91 (180/ 72 ) at 20:59