13-15 July 2013

The NCEP ensemble of GFS is suggesting another snow event next weekend, and I find it to be one of the more reliable guides at this range. Unfortunately the EC model (by far the best long range deterministic model) has been showing some pretty nasty tropical feed, indicating rain, not snow. We will have to wait for updates.


Update:  This is now clearly a rain event, unfortunately.  With the low stalling in the bight, there’s a chance the worst of it will miss the alps.  Rain is seriouly over-rated as a snow-melter anyway, particularly at this time of year.  For example, the heat in 25 mm of rain at 5°C (~520 kJ/m²) is only enough to melt about 1 cm of fairly light snowpack (at say 150 kg/m³).  The main melting effect from rain seems to be around the thin edges of cover, where melt and physical displacement can expose the dark substrate (those clever alpine plants), greatly increasing solar melting once the weather clears.

Note that NZ looks like enjoying yet another dump to low levels during this interval…


A wet northerly, as expected, with a total of about 35 mm at Perisher and Falls Creek, nearly all at about 3°C. The calculated rain-induced melt is around 1 cm of 150 kg/m³ snowpack. And yes, NZ got still more snow.

Prediction score: 8/10

00z 14/7/2013