Friday, May 31, 2013

Winter Rainfall - Climate Predictions Summary

Vines are now dormant. A wetter than normal season is more likely for most of southeast Australia. Climate influences include a warmer than normal eastern Indian Ocean, a neutral tropical Pacific, and warm local sea surface temperatures.
BOM Details

The chances of receiving above median rainfall during the winter period are 60 to 70% over most of southeast Australia. Such odds mean that for every ten years with similar climate patterns to those currently observed, about six or seven years would be expected to be wetter than average over these areas, while about three or four years would be drier.

Willunga Rainfall Predictions. Winter rainfall is important to flush soils of sodium chloride that has built up over summer irrigation. Click for a larger image.

Climate influences

The tropical Pacific has remained ENSO-neutral since mid-2012. Climate models surveyed by the Bureau of Meteorology suggest sea surface temperatures in the tropical Pacific Ocean are likely to sit on the cool side of neutral during winter 2013. 

SEA Rainfall Predictions.

Four of five international models surveyed by the Bureau favour the development of a negative Indian Ocean Dipole (IOD) event sometime during winter-spring 2013. A negative IOD during winter-spring increases the chances of above normal rainfall over southeast Australia, which is reflected in the rainfall outlook. 

Warmer than normal ocean surface temperatures currently surround much of the continent. Warmer ocean temperatures can provide more moisture to the atmosphere, which in favourable weather conditions (e.g., interactions with fronts or north-west cloudbands) may result in increased rainfall. 

Climatologists will continue to monitor conditions and outlooks closely for any further developments over the coming months, with information on the likelihood of El NiƱo available fortnightly at the ENSO Wrap-Up. For a summary of Pacific and Indian Ocean outlooks, please see the Climate Model Summary.

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