Another poor rainfall month has resulted in only 10mm for Geelong in May. Compared to the long-term average of 48mm, this was in the lowest 10% of all historical May totals, and completes a disastrous autumn, our driest on record since accurate records began in 1871. It was also our driest May since 1932, when only 10mm was recorded. Geelong’s autumn rain averages around 124mm; this year the total has only been 31mm, well below the previous driest autumns of 1993 (38mm) and 1908 (40mm).
The dry autumn was composed of falls of 7mm in March, 14mm in April and 10mm in May. In 1993 we had falls of 11mm, 16mm and 11mm, totalling 38mm, and in 1908 the figures were 6mm, 5mm and 29mm, totalling 40mm.
Despite the poor rains, the water catchments are at 56% of capacity, better than the 42% at this time last year. The Otways catchments are in better shape (66%) than the Moorabool (42%).
Dry weather helped to account for a fractionally higher (0.1 degree) than normal average temperature, with average daily maximums 1.0 degree above average, 18.2 compared to 17.2 degrees, but minimums 0.8 degrees below average, 7.3 compared to 8.1 degrees.
The dry and settled weather has been due to the dominance of a succession of strong high pressure systems forming over our latitudes, denying access to a series of weakening cold fronts and low pressure systems. This set-up in turn appears to have been brought about by a temporary and weakening El Nino-like situation in the Pacific Ocean which has caused inflows of drier air over eastern Australia. A full El Nino is now not expected to develop any further, although Geelong’s rainfall in the next 3 months is not expected to exceed the average.