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Above:
The AWN surface synoptic chart for 9pm local time shows a deep low tracking
across southern NSW. With a central pressure around 988hPa, it brings
unusually low barometer readings, strong winds and dust storms. Below:
The low draws hot dry air into NSW from the north while Victorians
to the south of the low shiver in cold southerlies with daytime temperatures
6 to 8C below normal.
This AWN chart for 8pm EDST shows wind streamlines pinpointing the surface
vortex over the NSW Riverina. The red isotherms show a tongue of plus-30° air
being drawn into central NSW, while the green lines of equal humidity
show air below 20% relative humidity being drawn into the centre of the
low.
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The wider area surface chart animation (9am
and 9pm today and 9am Wednesday) reveals that the NSW low is one of a pair,
dumbelling around one another. The NSW
low holds its unusual northerly latitude partly due to the dumbelling,
and partly because the pair is cradled by a ridge of high pressure running
from southern WA down to 60°S then NE to under New Zealand. BoM. |
 Extraordinary
synoptic situation brings heat and dust storms to SA, NT, QLD, NSW, cold
to VIC
In a
rare meteorological event today, a low moved east across southern NSW, slowly
deepening yet provoking
almost no rain. It did, however, generate significant wind which,
with the accompanying hot dry conditions, led to widespread raised dust and
dust storms
across SA, NT, QLD and NSW. South of the low, wintry conditions prevailed with
daytime temperatures 6 to 8 below average across Victoria and light snow flurries
between
8am and 1pm at Kosciuszko Chalet.
The low was originally the heat low that normally resides over northern WA
for most of the summer half of the year. This was displaced southeastwards
into SE WA by a strong upper trough on Sunday, then tracked east along
the SA coastline Monday, being kept to the north by a strong high pressure
ridge. Today, the low was captured into the circulation of a 985hPa low about
1000km SE of Hobart and the two began to dumbell around one another (see animation
at right). The former WA heat low moved inland near Adelaide late this morning
with a central pressure of 994hPa.
It then
steadily
deepened,
its lowest
recorded
pressure (corrected to mean sea level) over land being 986.7hPa at Griffith
Airport at 7pm. It split and weakened as it approached the Great Dividing
Range around midnight, with centres around 990 near Wagga and off the coast
near Newcastle. On Wednesday, it pirouetted away across the Tasman with its
partner, and by 10am EST Wednesday was the dominant performer in the pas de
deux with a central pressure of 982hPa.
Gales with wind gusts to storm force were widespread across SA, NSW
and southern QLD, with many locations reporting gusts
of 90km/h or above. The top gusts of 119km/h at Roma Airport and 100 at
St George and Charleville
Airports may have resulted from thunderstorm downburst winds being added
to the strong gradient winds around the low. Unroofed houses and downed
powerlines
and trees were reported from Roma, Charleville, St George, Quilpie and
Tara (80km west of Dalby), while an electrical storm in Toowoomba blacked
out 5,000 homes and unroofed a block of flats. Dust whipped
up by the wind in SA plumed
east
into northern
NSW and southern QLD, reaching maximum density late this afternoon and
into the night. Gale force winds also caused problems for emergency services.
Reports from specific centres:
- SA:
- Adelaide: strong winds from about 3am as the low approached
the coast brought down trees and powerlines, closed roads and blacked
out at least 20,000 homes. A tree crashed into a house in Woodville.
The worst affected suburbs were Netherby, Hackam, Paradise, Highbury,
Springfield and Salisbury.
- Woomera
visibility in dust 2km at 3pm. Top wind gust 95km/h.
Extensive areas of blowing dust were reported from parts of the
Northwest and Northeast pastoral districts.
- QLD:
- Quilpie visibility 500m at 3pm, less than
50m at 6pm
- Thargomindah
800m at 3pm and 9pm
- NSW:
- Tibooburra 300m at 3pm,
100m at 6pm, 400m at 9pm. Top wind gust 93km/h
- Wilcannia 900m at 3pm, 700m at
6pm. Top wind gust 91km/h
- Wanaaring 100m
at 3pm
- Broken Hill 98km/h wind gusts brought down trees, closed roads and
unroofed some homes and a gallery in Silverton. The SES had 39 callouts
- Ivanhoe
200m
at 6pm. Top wind gust 93km/h
- Nyngan 1km
at 9pm
- Hillston 900m at 9pm
- VIC:
As the low crossed NSW, hot dry air that has been setting October heat records
in QLD and the NT was ducted south resulting in some remarkably high night-time
temperatures and low humidities for October across central western NSW. Some
examples:
Location |
Time |
Temperature |
Dew Point |
Relative Humidity |
Walgett AP |
11pm |
31.6 |
-5.1 |
9% |
Cobar MO (Town) |
9pm |
28.0 |
-13.1 |
6% |
Forbes AP |
10pm |
28.5 |
-10.6 |
7% |
  |
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| Temperature departures from normal
today: Minimum temperatures left, Maximum temperatures right. BoM |
Heat
records fall
in QLD, NT
October
heat records again fell in QLD today as well as in the eastern NT. Mt
Isa Airport's top of 42.5 and Clermont's 40.5 were the hottest October
days in 36 and 41 years of computer records respectively. In the NT,
Centre Island's
new record of 39.2 was 1.3 above the previous October record in 27
years. Hot, windy conditions around Darwin caused another fire today
which threatened several houses at McMinns Lagoon and destroyed a
136-tree mango plantation.
In addition, October high minimum temperature records for both the NT and
QLD may have been broken. The overnight minimum of 31 (rounded) at Jervois,
about 400km NE
of
Alice Springs, may have eclipsed the previous highest Territory reading of
30.5 at Elliott in 1989, depending on the decimal point. In QLD, the situation
is also uncertain. The QLD October high minimum record is held by Boulia with
a reading of 31.4 in 1980. Trepell Airport, 150km NE of Boulia, recorded a
minimum of 32.9 in the 24 hours to
midday today. However,
official records are based on minimum readings taken for the 24 hour period
to 9am, and Trepell only reports maximum and minimum temperatures at 9am to
the
nearest
whole degree.
The minimum reported to 9am this morning was 31, though
the temperature in the screen at that time was 31.6.
News sources: ABC, Northern Daily Leader (Tamworth), AAP |
