From: david@mullara.met.unimelb.edu.au (David Jones)
Newsgroups: aus.snow
Subject: prediction
Date: 17 Aug 92 01:02:42 GMT
Distribution: aus
Organization: University of Melbourne Dept of Meteorology


>In article <djm.713421735@phobos>, djm@kbs.citri.edu.au (David Mills) writes:
>> Having just spent a week at Mt. Hotham, I'd have to say it is probably the
>> worst snow cover I've seen in August, since 1982.

>Earlier this year I posted that I had observed a good indicator of the coming
>snow season. This was based on moisture in the ground, or in this case the lack
>of it - the drought is still widespread.

>Those who had intricate theories why this (and any other predictor) would never
>work must be now wondering. After all we had the best start possible - early
>snow and lots of it.

          ^^^^

   Although the snowfalls were fairly good (especially in May), these came from
   relatively warm events which served to wash away much of the snow they deposited
   leaving the slopes bare in all but the highest locations. As for heavy, the
   highest total reported in Vic. for May was 30cm, at Buller. This is by no
   means a heavy snowfall for Autumn, c.f. 30cm in April 1987, ~30cm March 1991
   ~40cm May 1987, 100+cm 1968. 

>What about it guys. Do you still reject this observation?

>Big Al.
				      including "Big Al."
                                      ^^^^^^
Despite the best attempts of numerous people I am firmly of the belief that the
prediction of the Australian ski season is still not soundly possible. Although
such things as Sea Surface Temperatures (critical for rainfall), and analogues
with previous sequences of years may give hints, it appears that a given season
is unpredictable. In general in Australia we have typically 5 or so average seasons
followed by a bumper one, which is frequently followed by a poor one. This cycle
is evident many times in the last few decades, 

c.f. 1964/65 1968/69 1972/73 1981/82, (if my memory serves me right)

with the swing from a bumper to a dud season commonly associated 
with swings in the atmospheric circulation over the Pacific Ocean 
associated with the El nino atmospheric phenomena. However
this is not always the case as demonstrated by last years heavy season which 
followed the good snowfalls of 1990, (a season arguably the heaviest since 1964). In fact
despite large areas of Australia experiencing drought during Autumn and Winter 1991,
(see the ~100 day period in Queensland without rain!!!), relatively local effects and
a series of strong frontal passages resulted in the very heavy falls.

As for early snowfalls as predictors, look at the heavy falls in May 1982 for an
example of when these fail. Conversely 1968 is an example of when a heavy fall 
precedes a bumper season.

The use of moisture in the ground at a given location would also have to be questioned. 
The weather can and frequently is very different between given locations, especially
if they are well separated. I use August 1991 as a prime example, Vic and Southern N.S.W
were very moist while all of Northern Aust. and much of the central regions were
ravaged by severe drought. As for very wet periods indicating heavy snow, June 1991
was extremely wet through the SE and E regions of Aust. and yet the snowfalls were non
existent. The converse was the case in May, when the region was very dry but saw some
light snow and cool temperatures. 

Need I go on... The fact is the Australian snow seasons are made up of a series of
"unpredictable" frontal passages (and Precipitation events) which one has no
possibility of predicting (at present). Although sophisticated models are being developed
around the world to give prediction of rainfall for periods of months or more,
these are of limited use for snowfalls particularly in marginal snow
regions like ours where the role of temperature is critically important.

Finally Big Al. I would encourage you to ask anybody who has been to the snow 
in the last week. Conditions have rapidly improved from those a week ago, (which
were fair-poor, particularly in NSW due to heavy rain ~10 days ago).
I am of the opinion that your claim of verification seems somewhat premature. 
While 120 cm. (the official depth at Falls Creek at present) cannot be 
claimed to be excessive, it does lie in the range of normality.


David.