May weather puts a dent in drought deficits

May weather puts a dent in drought deficits

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Victorian rainfall totals (mm) from March 1 - May 31, 2019. Image: Bureau of Meteorology

Victorian rainfall totals (mm) from March 1 - May 31, 2019. Image: Bureau of Meteorology

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Bureau of Meteorology climatologist Jonathan Pollock, gives the autumn summary.

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Rainfall totals were mostly average to below average in Victoria this autumn, with days much warmer than usual. However, a wet May means the severe year-to-date rainfall deficiencies that covered roughly half of the state at the end of April have contracted to the far northwest.

Parts of the northeast and southwest received above average rainfall this autumn, thanks mostly to May's contribution. Some locations around the southwest, including areas around Geelong, had their wettest May on record.

Despite a wet May, autumn 2019's rainfall was 21 per cent below average for the state. Some parts of the Mallee and Central districts recorded totals in their lowest 10 per cent of historic autumn records (decile range 1). Western parts of the Mallee received less than half of their average autumn rainfall

Autumn 2019's daytime temperatures were in the warmest 10 per cent of the historic record (decile range 10) for most of the state, averaging more than 1 degree higher than usual. Overnight temperatures were mostly warmer than average too, especially in parts of the centre and east, where they were more than 1 degree higher than usual. The mean temperature (an average of the maximum and minimum temperatures) was the eighth highest on record for autumn.

The warmer and drier pattern looks set to continue into winter. The chance of above average rainfall this winter is low, between 30 and 35 per cent for most of Victoria. However, soil moisture down to 1m is currently near average for most of the state at the beginning of June, though soils remain drier than average for parts of Gippsland. And in more good news, water storages appear to have stopped declining, with Victoria's total storage level having risen from 42.4 to 42.8 per cent over the past month.

Daytime temperatures are very likely to be higher than usual this winter. Most of Victoria has a greater than 80 per cent chance for above average maximum temperatures. With more cloud-free days and nights expected, there is an increased risk of frost in susceptible areas.

Winter's outlook is being influenced by temperature patterns in both the Pacific and Indian Oceans. The Pacific is close to El Nio thresholds, but models expect these El Nio-like patterns to weaken during winter. However, a positive Indian Ocean Dipole (IOD) is forecast to develop during June and persist until spring.

Read the autumn summary at bom.gov.au/climate/current/season/vic/summary.shtml

- Jonathan Pollock, BOM climatologist

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