Today's situation in South-East Oz is interesting.  As you all know, a change is expected through late this afternoon.  The interesting thing is how warm the air is ahead of the change, with the forecast for Melbourne today having been amended to 37C.

My image of a classical change in SE Oz is very warm air ahead of it due to a long overland trajectory of northerlies.  It seems, though, the source of the warm air in the current situation is more one of advection at upper levels, say 850hP  where we have a long west-north-westerly trajectory, bringing warm and dry air from across the Nullabor and from central Oz.   Part of the reason this central Oz air is so warm (and so dry) is the fact that the continent has been so dry over the past two weeks, with that whopping, great anticylone at 500 hPa that has been sitting over us through this period.

Related to all this (and to the high temperatures) is the very deep mixed layers in the pre-frontal warm air.  Have a look at some of the current soundings at http://serva.sa.bom.gov.au/data/skewt/map.html (I'll put some of them on my web-page later).  Once the warming fills in the bit at the bottom, Melbourne will have a mixed layer extending up to 600hPa.  Mt Gambier's trace for 23Z last night shows one going up to almost 500 hPa.

Cheers

John McB