8-10 June


This fizzed, obviously, except many places seem to have scored about 10 cm of snow on the tail, which is better than a kick in the guts. The Bureau of Meteorology’s excellent winterised automatic weather station at Perisher Valley saw it like this (at 1738 m; click for link):

BOM Perisher Valley precipitation

BOM Perisher Valley temperature (red) and dew point

So the ‘second wave’ system brought ample precipitation (that 40 mm!), but the cold I was anticipating, perhaps hoping for, arrived too late — about mid afternoon Friday. Two degrees Celsius is occasionally cold enough for snow in Australia, but not from a warm, wet lower atmosphere. It’s instructive to check the thickness and freezing level for Thursday; this from the US GFS model’s ‘analysis’ (model initialisation) at 10:00am local time, as plotted by Weather Online in the UK:

GFS MSL pressure, 500 hPa geopotential height contours, and
500-1000 hPa thickness shading for Thursday morning

GFS freezing level for Thursday morning,
UK Weather Online

So the ACCESS-R prediction was a tiny bit out — the 500-1000 hPa atmospheric thickness over the alps looks to have been about 5460 m Thursday morning (the colour shading labelled ‘546’) rather than less than 5440 m. The freezing level was about 2000 m.

Not to labour the point, but the fusion temperature of water is immutable. From the point of view of snowfall, 1 °C too warm might as well be 10 °C. And for our marginal snow weather, a couple of degrees temperature increase will be pretty much enough to end it.


Update #4 (7 June):

Maybe this isn’t quite dead. BOM’s ACCESS-R is showing just about enough cold air around from early Thursday for mid level snow. It’s touch and go though, like so much of our snow weather. Why do people fail to notice how fragile it is.

(The 500-1000 hPa atmospheric thickness is an approximate indicator of average lower troposphere temperature; 5440 m — the blue 544-line — is often cold enough for mid level snow in Australia.)


Update #3 (3 June):

Ok, I’m kicking this a day later — to Thursday. The current system feeds into a second upper wave to form a traditional-looking winter surface pattern. I think it’s good for in excess of 20 cm.

Remember that 5440 m thickness (the thick blue dashed 544-line on the BOM chart) is usually enough for mid-level snow in Australia. (The 500-1000 hPa atmospheric ‘thickness’ is an approximate indicator of average lower troposphere temperature.)


Update #2 (2 June):

A massive upper system will bomb over eastern Australia on the weekend, bringing widespread rain — potentially flood rains on parts of the coast as one or several east coast lows develop. The question for our snow prospects is what happens to the wave following.

BOM ACCESS 200 hPa level (~12 km height) for Saturday

…And for Tuesday night

There’s still a chance of some significant snow, but the weekend disturbance is so strong that it appears to be disturbing the subsequent modelling. The three models I usually follow are still highly divergent.


Update #1 (31 May):

This one is still there, but drifting later and weakening, as lots do. There’ll be snow in there somewhere of course, but enough … no, probably not.

But it is nice to see plenty of moisture progged for our bit of atmosphere over the next week or two. Bodes well.


Original post (27 May):

It’s a long way out, but there’s a nice little lobe building on the Spag plot for early June, giving an outside chance of some proper snow on the ground for a long weekend opening. It’s a few years since we’ve seen one of those.