AUS: Characteristic spring weather brings extremes across the nation
Typical spring weather affected much of the continent today, with warm almost summery conditions across central and eastern states and a return to winter for much of WA. In between, where the two airmasses rubbed shoulders, storms continued a diurnal cycle of afternoon and evening development and morning decay.
|Precipitable water (mm) through the full depth of the atmosphere and CAPE instability index at 10am EST. COLA
The 10am EST surface chart and satellite image above, the temperature anomaly maps at right and the moisture and instability map at left are a textbook example of spring weather on a grand scale. Northwesterlies covered most of the eastern states, carrying warm air from the tropics and a broad stream of moisture from the NT into VIC and TAS. Overnight temperatures were between 6 and 12C above normal over a huge area, thanks partly to cloud cover but more to unusually high dew points for September slowing the normal overnight cooling process. The high moisture levels and light winds led to some persistent thick fogs in SA this morning, with Warooka on Yorke Peninsula still reporting visibility less than 50m at 9am.
Well above average maximum temperatures today covered a similar area to yesterday but were a few degrees cooler as cloud developed along the troughline in the moist and increasingly unstable airmass.
South of WA, the combination of a fairly deep secondary low and a high SW of Perth pushed cool, relatively dry southerly winds far into the state, bringing maximum temperatures 8 to 10C below normal in the south, where Ravensthorpe only just made double figures. Southern coastal areas and the nearby interior recorded between 5 and 25mm for the 24 hours to 9am in the onshore winds. As the cold front pushed into SA, Ceduna recorded a temperature drop of 7.8C in 10 minutes to 1.49pm.
Thunderstorms were again widespread in the northwest moisture band, yesterday's storms dying down during the morning, but firing up again during the afternoon in the area of greatest instability over western VIC, SW NSW and eastern SA. As yesterday, the storms moved east and southeast, giving the heaviest rain to upslope areas in NE VIC, southern NSW and northern TAS. However, storms penetrated right to the South Coast of TAS, with Maastuyker Island reporting a rare thunderstorm this morning.
The Harrietville flood raingauge, to the west of Mt Hotham, recorded 68mm between midnight and 9am Saturday for a 24-hour total of 80.6mm, supported by the nearby manual gauge reading of 76.0mm. Moderate rainfall and snowmelt across the Alps pushed the King, Kiewa and Mitta Mitta Rivers over minor flood levels by Saturday afternoon. In NSW, top falls for the 24 hours to 9am Saturday were on the SW Slopes: Tumut 38.6, Batlow 36.6 and Adelong 30.0. On Tasmania's North Coast, Lorinna recorded 28.4, Mole Creek 26.6 and Ringarooma 26.2. There were only a few heavy downpours captured by AWSs during the early hours of Saturday; see Saturday's downpours for details.
Strong winds were widespread, with 13 AWSs across WA, NSW, VIC and TAS recording 24-hour average windspeeds of 40km/h or greater to 9 this morning (see windiest). Cape Leeuwin (55.2km/h), Melbourne Airport (51.0) and Mt Wellington (50.8) were the highest. Top gusts were 109km/h at Thredbo Top Station and 104 at Mt Wellington.