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 Torrential
rain in SE QLD
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The surface situation at 10am EST today. Ex-TC Beni, though heading NW,
had moved more westerly during the early morning, closing the coast and
tightening pressure gradients on its southern flank. BoM |
Torrential rain fell between the NSW border and the Sunshine Coast today as
ex-Tropical Cyclone Beni curved briefly towards the QLD central coast. Between
50 and 200mm fell across Brisbane and the southeast coast in the 24 hours to
9am Tuesday, with many places recording over 100mm (see full listing for Tuesday).
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| Above: Precipitable water (mm) and tot-tots
index |
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| Above: 850hPa wind, humidity and temperature |
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| Above: 700hPa vertical velocity. All at 10am
EST. COLA |
An area of heavy rain crossed the southeast QLD coastline around 8am, and
lodged over the Gold and Sunshine Coasts and the Brisbane area for the rest
of the day, clearing slowly around midnight. Though the rain area remained
virtually stationary, it was fed by a moist, strong ESE inflow tightened by
the temporary movement of ex-TC Beni towards the coast during the morning.
The depression resumed its NW movement by late morning, and the heaviest falls,
between around 9am and early afternoon, coincided with its temporary excursion
towards the coast.
The 10am charts show why the heavy rain occurred. The broad surface situation
shows a strong onshore stream between ex-TC Beni, still maintaining its central
pressure of 1000hPa, and the 1028hPa High near Tasmania. The gradient is strongest
over the SE QLD coast between the 1016 isobar and the 1000 centre of the Low.
However, the intensification or rain over the SE coast came from a narrow
area of colder upper air, shown clearly on the 850hPa (about 1.5km) chart at
right.
This in turn enhanced upmotion in the lower atmosphere which is evident in
the marked
bullseye
of ascending air at 700hPa, or about 3km. It shows up, too, in the buff area
of high totals totals, an instability index. All this coincided with abundant
moisture, as shown both on the 850hPa chart as deep green (more than 90% humidity),
and in the precipitable water analysis. Precipitable water is the total depth
of liquid water that would result if all water vapor contained in a vertical
column of air could be "wrung out", leaving the air completely dry.
The heaviest falls (see the map below) were on and east of the Blackall Range,
in the Maleny/Nambour area, where orographic ascent wrung even more moisture
out
of
the saturated
airstream. Tewantin topscored with 194mm, closely followed by Maleny with 188,
Beerburrum Forestry with 186 and Landsborough PO with 174.6. Orography also
played a part in the 167.2 recorded at Springbrook, high on its ridge behind
the Gold Coast.
There were some remarkably heavy falls between about 9am and mid afternoon
(see Downpours box below for full details). Tewantin recorded 100.4mm in the
2 hours to 2pm. There was extensive flash flooding, and some creeks in the
northern Maroochy basin were in minor to moderate flood by late evening.
Galeforce winds gusted to 95km/h at Cape Moreton, producing
3 metre swells that closed most Gold and Sunshine Coast beaches for the day.
A Voluntary Marine Rescue boat rescued 12 people in two outriggers when they
got into difficulties in heavy seas near Hornibrook Bridge.
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| Rainfall distribution for the 24 hours to 9am. BoM Hydro |
On the 3rd a long-lived evening squall line produced wind gusts
to 96 km/h at Koolpinya, 30 kilometres east of Darwin and 94 km/h at Lee
Point, in Darwin's northern suburbs. Lightning also caused a 2 hour power
failure at Nightcliff.
NEWSBITS
|
Constant hot nights and daytime temperatures reaching
into the 40s are worsening the water shortage in Cobar NSW in an unexpected
way. The
shire's General Manager, Chris Blanch, told ABC News the town's 2,000
air conditioners are using a million litres of water a day. Even though
the
town's
water supply is expected to run out by June unless rain falls, Mr Blanch
says the air conditioning is essential because the heat and dust storms
have been unbearable.
Temperatures were around 10° above average around the South
Australian coastline today, reaching 36.3 in normally cool Mt Gambier.
By contrast, it was an unusually cool February morning in SW WA
where Northam recorded its lowest February minimum in 35 years of
computerised records.
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Victorian firefighters, whose backburning efforts have been hampered
by drizzly weather, faced a new adversity today. Thick smoke from the
fires accumulated across much of the state in calm conditions under
a High, severely restricting aircraft reconnaisance. The southern front
of the fire in the Mitta Mitta/Mt Beauty area was reported to be burning
strongly last night, while four major fires continue to burn in the
northern Snowy River National Park. Some 3,600 people and 30 aircraft
are currently fighting the fires, which extend broadly from Mt Buffalo
to near Deddick in the middle Snowy River valleys, a straight-line
distance of around 150km.
Over the border in NSW, the fires that have decimated the Kosciuszko
National Park are most active in the south and southeast around the Barry
Way south of Jindabyne eastwards to Delegate. Fires are also burning
actively near Perisher Valley and Guthega in the Snowy Mountains. |
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