Sunday, February 06, 2011

Yasi's Aftermath

Yasi has now weakened to a tropical low causing flash flooding, hailstorms and 90km/h winds in an arc from Queensland's north-west, through Alice Springs and as far south as Melbourne.
Huge amounts of warm, moisture-laden air brought across the continent by one of the largest cyclones in memory have been dragged south, colliding over Victoria with a large cold front heading north.
That front ''ingested'' the moisture, causing huge cloudbursts that dumped rainfall of up to 200mm in just two hours over Melbourne and regional Victoria. Thunderstorms were also recorded in NSW's south-west and hailstones ''as big as golf balls'' fell in Mildura.
While Victoria coped with flash flooding in suburban Melbourne early yesterday, forcing the rescue of 84 people from homes and cars, 4000 calls to the State Emergency Services and the closure of train lines, major roads and freeways, Sydney was in the seventh day of a heatwave.
But the Bureau of Meteorology said Yasi was not affecting Sydney's weather. The heat was due to a hot northerly airstream, caused by a slow-moving high-pressure system in the Tasman Sea, bringing hot air from the centre of the continent, coupled with high humidity, cloudy nights and high ocean temperatures.

Yesterday Yasi was hovering over the Northern Territory about 430km south-west of Mount Isa, causing heavy rain in far west Queensland.
For us sweltering on the south coast, south of Sydney, the news of snowstorms in the USA looked particularly appealing.
We have just sweated through our hottest night on record. The overnight low of 27.6 degrees was one degree higher than the previous record of 26.6, which occurred in February 1973. It was still 33.2 degrees at midnight, seven degrees above the average daytime maximum temperature.
The sweltering night followed a record-breaking seven days of temperatures over 30 degrees, a feat never before seen in 150 years of weather records.
But according to the Bureau the heatwave will finally, and quickly, come to an end today, Sunday, after a hot start to the day.
And as I type, the cooling southerly is starting to blow.

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