Storms soak Sydney and Brisbane, extreme | Australia weather Tue 3 Nov afternoon | Gus's Weather

Storms soak Sydney and Brisbane, extreme heat builds up north

[c06_radar_now]

GUS G'day, I'm Gus, and this is your afternoon bulletin for Tuesday the third of November.

GUS Heavy storms are soaking the south east right now, while extreme heat and fire danger build over the north west of the country.

GUS It's about 5 pm in Brisbane at the time this is uploaded.

GUS This is the Bureau of Meteorology's real national radar, not a model, and the newest picture is only about seven minutes old.

GUS The heaviest rain, right at the top of the Bureau's scale, is about 90 kilometres south west of Toowoomba in Queensland,

GUS and another patch just as heavy is about 80 kilometres west of Coffs Harbour in New South Wales.

GUS There's very heavy rain about 80 kilometres north west of the Central Coast, and another top of the scale cell west of Canberra.

GUS Sydney, Brisbane, Canberra and Darwin have rain on radar now, heavy in Sydney, Brisbane and Canberra, while Perth, Melbourne and Hobart are clear and Adelaide has light rain.

GUS Everything in this bulletin is indexed in the description, so if you're in a hurry, you can jump to the part you want from the chapters.

[c04_satellite]

GUS The real radar only sees where Australia's radar network reaches, so let's check the satellite, which measures how cold, and so how high, a storm's cloud top is, anywhere on the continent.

GUS The biggest storm this afternoon is over the Gulf Country, about 50 kilometres south west of Normanton,

GUS with a cloud top down to minus 87 degrees Celsius, covering about 100,000 square kilometres, roughly the size of Tasmania.

GUS That storm, and one near Kununurra, weren't matched by the model's simulated radar, so the model is running behind today. Trust the satellite and real radar for now.

GUS Darwin also has storm cloud sitting over it right now.

[c05_obs_now]

GUS Here's what's actually been measured on the ground, by Bureau of Meteorology weather stations, since 9 o'clock this morning.

GUS The wettest spot in the country is Badgerys Creek in western Sydney, with 45.8 millimetres of rain, a millimetre being how deep the water would be if it collected in a gauge.

GUS Mount Boyce in the Blue Mountains has had 28.8 millimetres, Grafton 23, Port Macquarie 18.2 and Miles in southern Queensland 15.6 millimetres of rain.

GUS The strongest gust so far is 106 kilometres an hour at Wellcamp Airport near Toowoomba, and Western Sydney Airport has had a gust of 93 kilometres an hour.

GUS That's measured, not forecast, so it tells you what's already fallen, not what's coming.

[c07_lightning_now]

GUS We also track lightning now, using the Blitzortung network, a volunteer lightning detection system that helps show where storms are actively firing between radar sweeps.

GUS In the last six hours there have been over 9,000 lightning strikes picked up across the country, and that number has been growing, with over 1,000 strikes in just the last hour.

GUS The busiest cluster is out at sea, about 46 kilometres east of Sydney.

GUS There's also lightning up near Mount Isa, though it's easing off there.

GUS This tells you where storms are active, not whether you're in danger, for any official warnings check bom.gov.au.

[c01_verification]

GUS Before I get into today's forecast, let's check how yesterday's call held up, so you know how much to trust what follows.

GUS My overnight low temperatures were close across the country, missing by less than one degree on average.

GUS My rain calls were shakier. I called rain for a few of the capitals yesterday and they stayed largely dry, so treat today's rain numbers as a guide, not a certainty.

[c02_mslp_fronts]

GUS Now, the tropics. I keep an eye on where the models think tropical lows might form, because that's how a cyclone season starts.

GUS The European ensemble is watching two areas well out in the Pacific Ocean near the international date line, with a good number of its model runs reaching tropical storm strength by later this week.

GUS Both are a long way from the Australian mainland and there is no official cyclone warning out right now, so this is an early watch, not a threat to Australia at this stage.

GUS I'll keep tracking it and update you if that changes.

[c02_mslp_fronts]

GUS So what's actually driving today's rain over New South Wales and south east Queensland? Let's look at the pressure pattern.

GUS There's a low pressure system about 80 kilometres south west of Orange in central New South Wales, at 1007 hectopascals.

GUS Think of a low like a drain in the weather: air spirals in and rises, feeding today's rain and storms.

GUS By Wednesday that low is forecast to shift out over the Tasman Sea and weaken, which is why the rain over New South Wales should ease through tomorrow.

GUS There's also a high pressure system out over the Great Australian Bight, at 1018 hectopascals, a calmer, sinking air mass keeping Western Australia and South Australia dry for now.

[c07_cape]

GUS To understand why storms fire in some places and not others, forecasters look at the fuel in the air, the moisture, and the energy.

GUS Meteorologists measure the energy a storm can feed on. They call it CAPE. Think of it like the petrol in a storm's tank.

GUS Just north east of Hervey Bay in south east Queensland, that's about 1200 joules per kilogram this afternoon, a decent tank for this time of year, enough to build solid thunderstorms.

GUS Similar storm energy is building out that way too, with the air properly humid, the moisture measure called dew point sitting around 21 degrees.

GUS Energy on its own doesn't make a storm. Something has to set it off, which is what we look at next.

[c12_index_map]

GUS Next, the lid, and the spin. A storm needs a weak spot in the warm air above it to break through, and some twist in the wind to help it organise.

GUS First, the cap. That's a layer of warmer air above the surface that acts like a lid on a pot and stops bubbles of warm air rising.

GUS Near Hervey Bay it's weak today, so storms should break through without much trouble.

GUS Now the spin. Forecasters measure how much the wind changes direction and speed with height, called wind shear, because that can tilt a storm's updraft and get it rotating.

GUS Near Hervey Bay it's about 65 kilometres an hour from the surface up to six kilometres, plenty to support a storm that can start to spin.

GUS Put the stored storm energy, the weak lid and the spin together and forecasters get a supercell number, what they call SCP.

GUS South east of Hervey Bay this afternoon that number works out high for this time of year.

GUS A high number says the environment favours a storm that can get organised. It's not a guarantee one will form, and it says nothing about hail size on its own.

[c10_sim_radar]

GUS Let's walk through tonight and tomorrow morning in the order the storms are expected to arrive, starting inland.

GUS Overnight into Wednesday, storms are likely near Mount Isa in western Queensland, with high downdraft energy that can drive sudden damaging wind gusts, hail and heavy rain for stock and the highway.

GUS Keep half an eye on the sky tonight.

[c10_sim_radar]

GUS Then, by Wednesday morning, the focus shifts to the coast.

GUS Thunderstorms are likely around Bundaberg and Hervey Bay, where Hervey Bay is home to about 58,000 people. Hail, damaging wind gusts and heavy rain are all possible there too.

GUS Storms like these can sometimes join into one larger cluster overnight, what's called a mesoscale convective system, which is just a group of storms that merges into one bigger system with heavier pockets inside it.

GUS That's part of why one street gets a downpour and the next one misses out.

GUS South east Queensland's ground is already wet, with about 26 millimetres of rain at Brisbane this week,

GUS above the usual 18 millimetres, using SILO rainfall records, so more of any new rain runs off instead of soaking in.

GUS If you're in Bundaberg or Hervey Bay tomorrow morning, keep the car under cover and an umbrella handy, since storms like these can arrive with little warning.

GUS So, the short version: inland overnight near Mount Isa, then the coast near Bundaberg and Hervey Bay tomorrow morning, both with a chance of hail and damaging wind.

[c18_model_compare]

GUS Let's check what the models say about rain over the Tasman Sea, just off Port Macquarie, where a storm is sitting offshore right now.

GUS Port Macquarie is home to about 48,000 people.

GUS The American GFS model has about 15 millimetres of rain there in the next 24 hours, the European model about 7 millimetres of rain, and the European AI model about 9 millimetres of rain.

GUS I'm leaning towards the lighter end, closer to the European model, since the American run is the wettest of the three today.

GUS Expect a decent soaking along that stretch of coast, including Coffs Harbour and Newcastle, typically 10 to 25 millimetres.

GUS If you're anywhere between Coffs Harbour and Newcastle this week, keep the gutters clear and an umbrella handy, since another 10 to 25 millimetres is likely on top of what's already fallen.

[c15_index_map]

GUS Now to fire danger, because the heat and dry air out in Western Australia's north west has pushed fire danger right to the top of the scale.

GUS Fire danger is rated with an index that factors in temperature, wind, humidity and how dry the vegetation is, called the FFDI.

GUS About 90 kilometres south of Karratha this afternoon it's reached a fire danger rating the Bureau calls extreme,

GUS about as high as that scale goes, with the dryness measure at the very top of its scale.

GUS The Bureau of Meteorology has an extreme heatwave warning out for the Kimberley and North Interior districts of Western Australia,

GUS and a severe heatwave warning for the Pilbara District, current as of 4:14 pm Brisbane time,

GUS with Karratha forecast to reach a top near 42 degrees and overnight lows staying above 28 degrees for several nights running,

GUS which is enough heat stress to be dangerous for anyone working outdoors or without good cooling.

GUS There's also a second, separate severe heatwave warning for the Pilbara District, covering an extended run of extreme heat through the rest of this week,

GUS with the Bureau warning of little overnight relief as lows stay close to 29 degrees night after night, so the heat keeps building with barely a chance to cool off.

GUS If you're anywhere in that part of the country, this is serious heat and fire risk together, so take it easy outdoors and keep up the fluids.

[c16_temp]

GUS The same extreme heat is sitting over the Northern Territory and into Queensland's Gulf Country.

GUS The Bureau has a heatwave warning out for the Tiwi and Arnhem districts near Darwin, rated extreme, as of this afternoon.

GUS The Bureau also has a severe heatwave warning for the Daly and Carpentaria Districts in the Northern Territory, current this afternoon,

GUS with overnight lows forecast to stay near 27 degrees and little cooling at night, on top of afternoon tops pushing toward 40 degrees further inland around Mount Isa.

GUS Darwin's own forecast top of 36 degrees gives you a feel for just how hot it is getting across that whole stretch of the Northern Territory.

GUS There's also a severe heatwave warning for Queensland's Peninsula, Gulf Country, Northern Goldfields, Upper Flinders, North Tropical Coast and Tablelands districts.

GUS Darwin itself, population about 122,000 people, is forecast a top of 36 degrees tomorrow with the overnight low not dropping below 27 degrees, a proper sticky Top End night coming up.

[c92_river_gauges]

GUS Away from the coast, some inland Queensland rivers are worth watching too, after recent rain further upstream.

GUS The Bureau of Meteorology has a moderate flood warning for the Balonne River from Surat to Warkon,

GUS where the gauge at Warkon is sitting at 5.92 metres and rising, with the river expected to peak a few metres above its banks later this week.

GUS There's also a moderate flood warning for the Bulloo River downstream of Quilpie and at Thargomindah,

GUS where levels are expected to stay in flood for several days as the rise moves slowly downstream through that stretch of the river.

GUS The Barcoo River at Coolagh, around Blackall and Isisford, is also in moderate flood and has risen about 1.3 metres since our last bulletin to 5.4 metres.

GUS The Hunter River around Newcastle is rising too.

GUS The Derwent River at New Norfolk in Tasmania is rising gently, and the Southern and Bremer rivers near Perth and Adelaide are quiet and steady.

GUS How bad any flooding might get is always on bom.gov.au.

[c90_events]

GUS A quick look at today's and this week's big events, because the weather matters for a few of them.

GUS It's Melbourne Cup day, and the race itself at Flemington looks dry with a top of 17 degrees, nothing to worry about there.

GUS In Newcastle, an AFC Elite match tonight has about 5 millimetres of rain and a thunderstorm chance, so if you're headed along, know that play can stop for lightning.

GUS Later in the week, Newcastle's Rugby League World Cup semi final on Saturday is tracking wetter, around 13 millimetres with gusty wind, so pack a poncho if you're going.

GUS Everything else on the calendar this week, including the rest of the Melbourne Cup carnival, looks fine weather wise.

[c20_town_table]

GUS Now the lap of the capitals, today's top, tomorrow's low and high, and the rain.

GUS This is the one place in the bulletin where I go through all eight capitals, so if you only want your own city, this is the bit to listen for.

GUS Brisbane: today's top was 26 degrees, tomorrow's low 19 and high 32, with about 15 millimetres of rain, so keep an umbrella handy.

GUS Sydney: today's top 25 degrees, tomorrow's low 18 degrees and high 24 degrees, with about 10 millimetres of rain likely, so pack a jacket and an umbrella.

GUS Melbourne: today's top 18 degrees, tomorrow's low 8 degrees and high 22 degrees, with barely any rain,

GUS nothing to worry about, though it is Melbourne Cup day so you know the drill about hats and heels on soft grass.

GUS What did one high pressure system say to the low? You're bringing me down. That one's for the dads.

GUS Canberra: today's top 21, tomorrow's low 9, high 24, about 8 millimetres of rain.

GUS Adelaide: today's top 20 degrees, tomorrow's low 14 degrees and high 18 degrees, with next to no rain, good drying weather, so the washing's laughing.

GUS Perth: today's top was 19 degrees, tomorrow's low 12 and high 25, with no rain forecast, dry as a bone and nothing to worry about.

GUS Hobart: today's top was 18 degrees, tomorrow's low 9 and high 19, with next to no rain, a jumper and a cuppa kind of morning down there.

GUS Darwin: today's top 36 degrees, low 27 degrees, with about 3 millimetres of rain, hot and sticky, the air conditioner earning its keep.

[c20_town_table]

GUS You've just had today's and tomorrow's numbers for every capital, so I won't run through that list again.

GUS This chart looks further out, days two through eight, using a longer range European model,

GUS which is a rain and temperature signal only, it doesn't tell us about thunder or hail, so I'll treat it carefully.

GUS For south east Queensland: Saturday there's plenty of the stored storm energy we looked at earlier building up, but nothing obvious yet to set it off, so it's one to watch rather than bank on.

GUS For the Top End: that stored storm energy keeps building through the week, but there's no clear trigger lined up yet, so storms could easily fizzle rather than organise.

GUS It's the build up season, where the steady trade wind rain of winter gives way to unreliable afternoon storms before the real monsoon rain arrives in December.

GUS For the New South Wales coast: a quieter run Thursday and Friday, then rain looks like returning later in the week, heaviest up around Newcastle on Saturday.

GUS The weekend verdict, since that's what most people want to know: south east Queensland looks like storms are possible Saturday as that stored energy builds,

GUS Sydney stays quieter with rain returning Saturday heaviest up near Newcastle,

GUS Melbourne looks like showers are possible Friday then a quieter, drier weekend with Saturday reaching only 12 degrees and Sunday 15, and Canberra looks dry, cooling to a top of 16 by Sunday.

GUS Of the four, Saturday in south east Queensland and Sunday in Melbourne are the days to watch.

GUS Days two and three in this outlook are fairly reliable, days four and five are a guide,

GUS and anything from day six onward is only a signal that can change completely by the next bulletin, because small errors in the model grow bigger every day. I'll keep updating it.

[c06_radar_now]

GUS Overall confidence in today's numbers is high, which in plain words means the models broadly agree on that low pressure system and on rain amounts at several of today's storm spots.

GUS The softest spot is the rain totals right at the storm cells themselves.

GUS My sky watching tip for today: if you're under any of those storm cells, watch for the sky turning a greenish grey before a burst of heavy rain, that's often hail bearing cloud.

GUS All the official warnings are kept up to date at bom.gov.au.

GUS My next bulletin is tomorrow morning.

GUS If you've got a weather question, or want to tell me what the sky's doing where you are, put it in the comments and I'll get to as many as I can.

GUS Thanks for spending part of your afternoon with me.

GUS Stay curious, and keep a brolly handy.

GUS Gus's Weather is a PandaVision production.