Tuesday, September 22, 2015

Early Rainfall or Not - late 2015?

The BOM recently issued the late August 2015 assessment of onset of the rain season across N Australia.  For the Darwin / Daly region, a slightly higher chance now of earlier rain that exceeds the 50mm accumulation. 

Maybe for the Top End it is now somewhat confusing as it could be argued that it is about evenly poised between early and later accumulation of 50mm of rain, as the difference is quite small for earlier rain.  Is there much difference between 5% either side the 50%?

I think there are serious quibbles about the definition used - 50mm of accumulated rainfall after September 1, but that is what they are using at present.  There is no value apparently placed on close events nor size of an individual event or period between events, features that could be more relevant for effective rainfall.  More work needed in this space I think.

However, some progress is being achieved.

Recent analysis is available here - 


with additional links to further mapping on adjacent pages.

The BOM links to this rainfall outlook do seem to indicate a good rainfall situation for central Australia though with more rainfall considered likely for the pre End of year period.

If you think the analysis needs more work, contact the BOM!   The more that do, the greater likelihood of further R and D on this important area.


This was written a month ago, and yes, there was some early rain, in some cases more than 50mm.  BUT........it has been extremely dry since and the pattern of continuing dry weather at least around Darwin seems to be likely to continue.  Any pasture growth from those early events is well and truly now dried off.

Would 50mm after 1 October be more appropriate as a measure of early seasonal change, rather than 1 September?

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