NSW: Unusual synoptic setup brings rain, wind
One of the strongest high pressure systems in recent years and an
unseasonable upper trough across northern QLD brought patchy moderate rain
to parts of QLD and NE NSW overnight and today. The high of 1043hPa dominates
the synoptic chart above and produced a strong pressure gradient and squally
the full length of the QLD east coast, extending to the NSW North Coast.
The high was at its strongest around 9 this morning in the dense cold air
of the Snowy Mountains region of NSW. The highest pressure recording at a sub-alpine
station was 1043.2hPa at Khancoban at 9am; high elevation stations registered
as much as 1044.1 at Thredbo Top Station at 9am, but with readings taken above
about 800m the assumptions used to reduce the pressure to mean sea level introduce
too many uncertainties for the measurements to be comparable.
The strong pressure gradient was responsible for blustery winds the length
of the QLD east coast with top gusts of 95km/h at Double Island Point north
of Brisbane and 100km/h on Green Island offshore Cairns. Heavy showers in the
southeasterlies built up substantial rain totals to 9am on the NSW North Coast
and QLD Gold Coast, with Tweed Heads recording 62.0mm, Ballina Airport 39.0
and Coolangatta Airport 37.4. Most of this fell in a few hours around midnight,
Ballina Airport registering 24mm in the 6 hours to 3am. Further heavy showers
this evening gave Ballina Airport 26mm between 6 and 8pm.
The effects of the strong southeasterlies were intensified across northern
and central QLD by an upper trough which, unusually for winter, moved into
the state from the NT yesterday bringing a broad cloudmass and patchy rain.
central and NE QLD recorded 5 to 15mm to 9am, with the heaviest falls on the
North Coast. Babinda PO recorded 134mm for the 2 days to 9am Thursday, but
the heaviest rain appears to have occurred around the middle of today with
nearby Innisfail reporting 40mm between 9am and 3pm. Townsville Airport recorded
20.2mm in the 24 hours to 9am Thursday, giving the city a total of 59.4mm since
1 June during its "dry" season compared with an average for June
+ July of 32.9. Possibly due to the unseasonable "wet", there were
9 separate vehicle crashes in and around the city during today.
Inland, there were two
areas of heavier rain: one inland from Charters Towers gave Strathtay Station
47.6mm and Pentland 46mm over the 2 days to 9am Thursday while a strip to
the southwest included 28.2 at Navarra and 23.0 at Jochmus.
The cloudmass resulted in an abnormally warm night and cool day; the temperature
anomaly maps above show that parts of QLD had minima 6 to 9 above average and
maxima 6 to 9 below.
Warm day precedes wet, windy change
Warm northwesterlies and a rain-bearing trough preceded an active cold front
that crossed the capes in far SW WA late this evening. The northwesterlies
saw top temperatures up to 8 above average, with Narembeen, 250km E of Perth,
experiencing its warmest July day in 34 years with a high of 25.0C. Albany
and Cape Naturaliste, both with lengthy weather records, both came within
1 degree of record territory with tops of 21.8 and 21.0 respectively.
The trough moved up the coast between mid afternoon and late evening giving
several hours of moderate rain with some heavy dumps. Cape Leeuwin recorded
15.6mm in 26 minutes shortly after 3pm. Most locations recorded 10 to
20mm and some up to
to 9am Thursday. The highest wind gusts were 113km/h at Cape Leeuwin, 106
at Cape Naturaliste and 93 at Rottnest Island.
TAS, QLD: Strong average wind speeds
The Windiest column below is showing up some
high average windspeeds as a result of the strong pressure gradient around
the SE AUS high. This column gives the top anemometer wind runs around the
country, both from manned and automatic weather stations. The "wind run" is
simply the number of kilometres of wind or air that blows past the cup anemometer
during the 24 hours to 9am, and the figure in brackets is this figure divided
by 24 to give an average windspeed.
Maatsuyker Island, off the south coast of TAS, confirms itself as the windiest
place in the country with 3240km of air blowing past the anemometer cups in
the 48 hours to 9 this morning. That's an average windspeed of 67.5km/h. Gale
force category begins at 63km/h. In the 24 hours to 9am Thursday, however,
coastal stations in QLD take first three places with average speeds of 58.3km/h
at Double Island Point Lighthouse, 56.8 at Cape Moreton Lighthouse and 53.0
at Hamilton Island Airport.