Melbourne's biggest downpour in five years made October become the wettest month in five years and wettest October in 35 years, according to weatherzone.com.au.
The downpour, on the last weekend of the month, brought 55 millimetres of rain to the city in 20 hours from 1pm on Saturday, leading to flash flooding. About 30mmm fell during the Derby Day races at Flemington. The 55mm was the highest daily total since February 2005, when a whopping 113mm fell in 24 hours.
This rain took Melbourne to 135mm for the month, making it the wettest month since February 2005, when 167mm fell. It also became the wettest October since 1975, when 150mm was recorded in the month.
October's 135mm is more than double the monthly average of 67mm, an amazing achievement considering there were only 13 rain days, one fewer than normal. This 135mm figure stands in stark contrast to the meagre 22mm in October last year.
"This October's rain cam almost entirely from three weather systems, one in the first week, one in the middle of the month and another last weekend," Weatherzone meteorologist Brett Dutschke said.
"The three weather systems all contained high amounts of moisture, flowing in from the tropics," Dutschke said.
"With 95mm of the 135mm falling in just three days, most of it falling at night, it left plenty of time in the rest of the month for daytime temperatures to be warmer than normal."
The average maximum was 20.6 degrees, a degree higher than the long-term average of 19.6.
"It was only our warmest October in two years. And we can't blame the lack of sunshine, we averaged eight hours per day, nearly two hours more than in a normal October."
"With all of this extra sunshine we would've expected warmer days. But we just didn't get many days with strong northerly winds and many of our sunniest days were cool with sea breezes."
Regarding overnight temperatures we averaged a minimum of 10.9 degrees, more than a degree higher than the long-term 9.6 and the warmest October in only two years.
Combining overnight and daytime temperatures it was the warmest October in two years with an average of 15.8 degrees, about a degree higher than the long-term, norm.
Elsewhere in Victoria it was wetter than normal October in most central and northern parts, the exception being large areas of the Western, West and South Gippsland and East Gipssland.
In the Mallee, Mildura gained 92mm, three times the average and their wettest October in 34 years. In North Central, Castlemaine had 146mm, more than twice the average and their wettest October in 35 years. In the Northeast, Rutherglen's massive 179mm for the month is three times the average and their wettest October in 98 years of records.
"Looking ahead to the rest of spring and summer, rainfall and temperatures should be near-or-above the long-term average. This is due to the current La Nina and warmer than normal western Pacific and Indian oceans," Dutschke said.
© Weatherzone 2010
11:39 EDT El Nino is one extreme of the El Nino-Southern Oscillation (ENSO) phenomena, in which La Nina is its counterpart.