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recorded at places across northern NSW. This area of concentrated dust
does not appear in Figs. 3(a), (b) but does show as a weak concentration
later in the period (Fig. 3(c)). The most probable cause of this inconsis-
tency early in the period was the thick cloud near the front which is evident
across northern NSW in Figs. 3(a), (b) but not in Figs. 3(c), (d).
5.3. Synoptic differences between the two case studies
For both cases the low-level frontal movement and associated wind speeds
were sustained across eastern Australia from the source to the east coast.
In this case study of February 2, 2005 there was cloud and rain over the
southern portion of the front in Victoria. There was no rain and little cloud
where the dust occurred in the first case study, which is more typical of the
climatology.
6. Conclusions
From 1995 to 2005 there were 55 “dust days” in central eastern Australia,
as recorded by the Australian Bureau of Meteorology's synoptic stations.
These 55 days consisted of 43 associated with fronts, with 24 classified
as either embedded in the zonal westerlies in the GAB or in westerlies
generated by low-pressure systems in the GAB. The remaining 19 were
associated with fronts over eastern Australia where high pressure systems in
the GAB produced postfrontal south to southeast winds. The case studies
both were in the latter group. The first synoptic group is characterized
typically by single or two consecutive days on which dust was reported.
The second day in a sequence was usually when a front crossed the east
coast thereby causing a translation of dust reports to concentrate in coastal
areas.
However, there was one sequence of six days in the second synoptic group
when dust was reported over western QLD under the influence of persistent
south to southeasterly winds in that area while the preceding frontal sys-
tems typically stagnated and/or weakened over central QLD. An overview
was described of each of two case studies where recent dust storms were
reported. The two case studies of October 23, 2002 and February 2, 2005
were similar insofar as frontal systems developing in the GAB intensified
across the dust source region and the associated wind changes carried the
dust across the east coast of Australia. The antecedent soil conditions in the
dust source region together with the synoptic scale frontal movement and
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