Monday, 30 April 2001

MONTHLY CLIMATE SUMMARY - VICTORIAN REGIONAL OFFICE

Heavy rain drenches Victoria in April

The low pressure system responsible for the rain formed within a trough in the easterlies over eastern New South Wales. It gradually intensified in situ, sucking in moist air from the Tasman Sea to the south-east. The air mass was quite unstable, leading initially to widespread thunderstorms and later to steady rain as the air mass lifted over the ranges. There were many ground strikes from lightning associated with the thunderstorms. The low then drifted slowly south and over eastern Bass Strait. Winds then tended south-westerly, but heavy rain continued because the air originated from over the Tasman Sea and had a high moisture content.

The state's wettest spot was Mt Sabine (a flood warning rain station in the Otway Ranges), which received 506 millimetres in four days. Melbourne received more than 25mm on three consecutive days, the first time this has happened since 1972. However the north-west of the state missed out because the uplift over the Great Divide led to most of the rain being deposited on and south of the ranges.

With the exception of this one major event, and a minor rain event about a week earlier, April 2001 was predominantly fine, with clear skies accompanying mostly below-average night-time temperatures and above average day-time temperatures.

In the Melbourne CBD, 124mm of rain fell during April (normal 53mm), 109mm of which fell in a four-day period. April minimum temperatures averaged 12.1 degrees Celsius (normal 11.7 degrees), while maximum temperatures averaged 20.6 degrees (normal 20.7). Melbourne's daily weather conditions for the month are presented in table 3.

Ends

Further information:
Dr Harvey Stern, tel: (03) 9669 4949, e-mail: h.stern@bom.gov.au