30
BAMOS
Dec 2017
Science Article
Observed zone of increasing wind
speeds and tornado events in
Tasmania, Australia
Anton Kole
Recently completed Honours student (first class), The University of Tasmania
email: [email protected]
Abstract
While wind speeds around some parts of Tasmania have been observed to be increasing over time, some areas have been
decreasing. The increasing wind speeds currently form a zone from the central northern part of Tasmania, through to southeastern
Tasmania. Within the increasing wind speed zone (the zone), wind speeds vary from an increasing average of 1.12% to 20.78%
every decade. Outside of the zone, the average decreasing wind speeds vary from 0.26% to 11.99% every decade. The frequency
of tornado sightings in Tasmania has been steadily increasing since 1928, with approximately 86% occurring within the zone. If
the wind speed in the zone continues to increase, tornado events may also correspondingly increase. Despite some remaining
concerns about the quality of long-term wind observations, the observed changing patterns may potentially signify the initial
conditions of an emerging Tasmanian ‘Tornado Alley’. Although elements leading to these conditions are not yet fully understood,
climate change, the Tasmanian geomorphology, and deforestation practices may be contributing factors.
1. Introduction
With extreme weather event intensity and frequency expected
to increase over time due to climate change (White et al., 2010),
a previous study found that in some areas of Tasmania wind
speeds have been steadily increasing (Kole, 2016). Extreme
wind events may cause severe damage to crops, private
property, and public infrastructure. Tasmanian businesses,
crops, lives, and economy, have been adversely affected by
such events (ABC, 2014; ABC, 2015). Understanding which
areas of Tasmania are most affected by increasing wind speeds
may assist stakeholders to be better able to prepare for, and
adapt to changing climatic conditions. While a previous report
has provided a range of wind speed projections based on
derived information, modelled hazards, and computational
methodology (Cechet et al., 2012), this study aims to assess
and provide stakeholders with information as to which areas
of Tasmania are potentially likely to experience increasing wind
speeds over the coming decades based on observed trends in
measured wind speed records.
2. Data and methodology
2.1 Study area
The area of study included all of Tasmania, Australia, and
its smaller satellite islands. Being the largest island State of
Australia, Tasmania has a land mass of 68,423 km², is located
42°S 147°E, and has a population of approximately 509,965
people (ABS, 2007; ABS, 2016). Centrally located and extending
from northwest to southeast, Tasmania’s central highlands
consist of numerous plateaus, lakes, and mountain ranges.
2.2 Data collection
All wind speed data were obtained from the Australian Bureau
of Meteorology (Bureau of Meteorology) website (Bureau
of Meteorology, 2016a; Bureau of Meteorology, 2016b). The
statistical weather data collected consisted of 9 am and 3 pm
thirty-year mean annual wind speeds from 22 different weather
station sites (sites) from across Tasmania (Table 1). Data in Figure
1 were also included from sites that were no longer currently
collecting wind speed data, stopping as far back as 1959.
The coordinates of all sites were also obtained for mapping
purposes.
2.3 Methodology
Wind speed data collection and thirty-year mean annual 9
am and 3 pm wind speed calculations were performed by
the Bureau of Meteorology, and subsequently made available
online (Bureau of Meteorology 2016a; Bureau of Meteorology
2017). Climate statistics were derived only when there was at
least 10 years of data available (Bureau of Meteorology 2007).
An average of the 9 am and 3 pm thirty-year mean annual wind
speeds from each of the weather stations were calculated, and
used throughout this study as data-points (Figure 1 and Figure
2).