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Weather –
October 2009, Vol. 64, N
o. 10
281
I’m dreaming of a...Emilie HobbsWootton Upper School, Bedfordshire
As soon as the few short weeks of summer
come to an end we turn our thoughts to
weather at the other end of the scale. That
is, snow. And along with this dream of pure
ice crystals tumbling out of the sky inevitably
comes Christmas; the dream of a magical,
and always much too rare, white Christmas.
Admittedly, I am a fan of these exceptional
events of nature, and relish any chance to
discover anything which would help me to
anticipate them accurately.
This chance came sooner than expected.
As the tradition of top maths sets goes, our
class had the privilege of two maths GCSEs,
not just one – the extra being Statistics
– a useful but not always thrilling sub-
ject. As usual, coursework was involved, and
we were left with the Christmas holidays
to think of a theme. Having high hopes
for one myself, I chose to explore white
Christmases.
The question I initially wanted to answer
was fairly simple: where is the best place
to live (in the UK) if you want a white
Christmas? This expanded, not only to loca-
tions within the UK, but also within different
periods of time. Choosing nine towns/cities
spread across the UK for which I could find
reliable data, I was able to produce various
graphs and statistics tracing back to the
1960s which revealed interesting results.
Figure 1 shows the total number of white
Christmases every year from 1960 to 2000,
for the nine towns I had chosen (Table 1).
Although there is no clear trend shown in
Figure 1, it does have an interesting pattern.
The first seven years had at the very least
one white Christmas, but as time went on,
this regularity seemed to deteriorate. From
1982 to 1992, on only three occasions did
any of my chosen locations have a white
Christmas. In 1992 and 1994, none of the
locations had a white Christmas and in 1996
just one experienced it. Yet in1993 and 1996,
two-thirds of the towns enjoyed a snowy
sprinkling on Christmas day.
Since these results were more complex
than I had anticipated, I decided to investi-
gate the matter a little further. I produced a
second graph (Figure 2) which further clari-
fies these results. To create it, I calculated
a five-point moving average from the data
presented in Figure 1, and presented it as a
percentage of the number of towns (nine)
which could have had a white Christmas. I
also calculated the standard deviation and
expressed it as a percentage of the mean, in
order to compare both on the same graph.
As you can see, it suggests a slight decrease
in the average number of white Christmases,
but a more interesting increase in the stand-
ard deviation. This confirms my thoughts
of less regularity by showing an increasing
range of snowfall between years.
Whatever the causes are, my project
definitely suggests a change, not in the
amount of snow, but in the pattern. After
all, if a simple statistics project can show
this, then there must be something going
on. Considering the small number of white
Christmases Great Britain has experienced
in the past few years, I know I am not
alone in feeling it’s about time I enjoyed
one. Although I won’t be travelling up
to Lerwick (the winning location of my
project), I will definitely be following the
weather forecasts with unusual attention
during this festive season, keeping my fin-
gers tightly crossed.
Correspondence to: Emilie Hobbs,
Wootton Upper School, Bedford, MK43 9HT, UK.
Email: [email protected]
© Royal Meteorological Society, 2009
DOI: 10.1002/wea.389
Table 1
Towns used to derive the statistics.
Aberdeen
Aberporth
Belfast
Birmingham
Bradford
Glasgow
Lerwick
London
St. Mawgan
Figure 1. Number of white Christmases between 1960 and1999.
0
2
4
6
8
1960
1962
1964
1966
1968
1970
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
Year
Num
ber
of w
hite
Chr
istm
ases
0
50
100
150
200
250
1960 1970 1980 1990 2000
Year
5-po
int m
ovin
g m
ean
perc
enta
ge a
vera
gean
d pe
rcen
tage
sta
rdar
d de
viat
ion
Mean % standard deviation as % of mean
Figure 2. Mean and standard deviation of white Christmases between
1960 and 1999.
