Sydney storms tonight, extreme heat | Australia weather Wed 4 Nov afternoon | Gus's Weather

Sydney storms tonight, extreme heat and fire danger up north

[c06_radar_now]

GUS G'day, I'm Gus, and this is the afternoon bulletin for Wednesday the 4th of November.

GUS The headline for most of you this afternoon is storms building near Sydney tonight, so stick around for that.

GUS It's about 3 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 about 6 minutes old.

GUS The heaviest rain right now is sitting over Victoria, near Ballarat, Geelong, Warrnambool and Melbourne itself, and also near Katherine in the Northern Territory.

GUS Around the capitals, Melbourne and Canberra have heavy rain on the radar right now, Sydney and Brisbane have lighter rain, and Perth is clear.

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

[c05_obs_now]

GUS Before we go further, here's what Bureau of Meteorology weather stations have actually measured falling in millimetres of rain since 9 am this morning, not a forecast.

GUS The wettest spot in the country is Ferny Creek in Victoria's Dandenong Ranges, with 13.4 millimetres measured there this morning.

GUS Hamilton in western Victoria has had 9.6 millimetres, and King Island in Tasmania 9 millimetres, with rain still falling at both.

GUS The strongest gust anywhere today is 70 kilometres an hour at Casterton in western Victoria, with Lameroo in South Australia close behind at 65 kilometres an hour.

GUS So Victoria and Tasmania are the wet corner of the country this afternoon, matching what we just saw on the radar.

[c04_satellite]

GUS Now let's look up, not down. This is the Himawari satellite, which measures how cold the tops of clouds are.

GUS The colder a storm's top, the higher it has punched into the atmosphere, and the stronger it usually is.

GUS There's a storm south-east of Ngukurr in the Northern Territory with a top of minus 61 degrees Celsius, genuinely severe looking.

GUS Another sits over the Gulf of Carpentaria north-east of Gununa, a top of minus 60 degrees, in roughly the same league.

GUS Closer to home, Sydney and Hobart also have some deep storm cloud nearby right now, cold enough to matter.

GUS Brisbane, Adelaide, Perth and Canberra have nothing like that overhead at the moment.

[c07_lightning_now]

GUS We also track lightning now, using the Blitzortung network, a volunteer set of lightning sensors around the world.

GUS In the last hour lightning has been picking up again, even though it's eased off a bit over the last six hours.

GUS The busiest cluster is about 100 kilometres west of Tennant Creek in the Northern Territory, out over the highway and cattle country.

GUS There's also a cluster near Colac in Victoria, not far from Geelong, and a couple more out at sea south of Warrnambool.

GUS None of that means anyone's in danger right now, for live warnings always check bom.gov.au.

[c01_verification]

GUS Quick check on how I did yesterday, because a good forecaster owns their misses as much as their hits.

GUS My overnight lows were close everywhere except Perth, where I said a low of 16.4 degrees and it only got down to 13.6 degrees.

GUS On rain, I got it right at 12 towns out of 47 towns checked and wrong at 10 towns, with the Gold Coast my trickiest miss.

GUS Over the last seven days, about 80 per cent of my temperatures have landed within 2 degrees, a solid track record.

[c02_mslp_fronts]

GUS Here's the pressure pattern across the country right now. High pressure systems are the lazy, settled ones, lows and troughs stir things up.

GUS A high near Kalgoorlie in southern Western Australia is keeping that state calm, with another sitting out in the Coral Sea near Cairns.

GUS A broad area of low pressure is parked over the Great Sandy Desert in Western Australia, and another over the eastern Northern Territory near Mount Isa.

GUS Out over the Tasman Sea, well south-west of Lord Howe Island, there's a weak low that will deepen over the next day or two.

GUS A fast jet stream, winds over 250 kilometres an hour high above the ground, is streaming across eastern South Australia right now.

GUS That fast upper wind helps storms organise by changing speed and direction with height, something we'll come back to over Sydney.

[c02_mslp_fronts]

GUS Because it's cyclone season, I always check the tropics first, even on a quiet day.

GUS There is no official tropical cyclone warning anywhere near Australia right now, and nothing forecast to form in our waters over the next two days.

GUS Ensemble models are flagging a couple of early-season disturbances out over the Coral Sea and the open Pacific, thousands of kilometres from our coast.

GUS They're a long way off, confidence is very low, and I'm not going to pretend otherwise. I'll keep watching and update you if that changes.

[c03_upper_500]

GUS Now the headline story. Sydney is in line for thunderstorms this evening, so let's work through why, step by step, like a forecaster would.

GUS See the marker just north-east of Sydney, out over the Tasman Sea. That's where our storm hotspot for tonight sits.

GUS The air there is warm and moist, with a dew point, a measure of how much moisture is in the air, of 17.4 degrees.

GUS A sea breeze and the afternoon heating are enough today to get that moist air rising, without needing a big weather system to help.

GUS So this isn't a major system moving through, it's a warm, humid afternoon doing what warm, humid afternoons do near the coast.

[c07_cape]

GUS Now the fuel. Meteorologists measure the energy a storm can feed on and call it CAPE, think of it like the petrol in a storm's tank.

GUS Near Sydney this afternoon there's about 1250 joules of that stored energy, a decent tank, enough to build some solid thunderstorms.

GUS There's also a lid in the air, a layer of warmer air above that stops rising bubbles of warm air, like a lid on a pot.

GUS Today that lid is worth about 151 joules of resistance, a real but not very strong lid, so it should break by this evening.

GUS Once it breaks, the warm moist air near the ground should be free to punch upward into proper thunderstorms.

[c11_shear]

GUS Next, how the wind changes with height, forecasters call that shear, picture it like layers of traffic moving at different speeds.

GUS Near Sydney tonight that wind change is around 62 kilometres an hour through six kilometres of sky, which is decent.

GUS That's enough shear to help storms organise and last, but the spin number, what's called the supercell composite, is low tonight, about 0.3.

GUS So storms that can start to spin, strong enough to count as a supercell, look unlikely tonight, this should mostly be ordinary but gusty thunderstorms.

GUS There's also good downdraft energy, about 620 joules, which powers the cold rush of air out of a storm's base.

GUS That points to a real chance of some locally damaging wind gusts under any storm that forms, along with hail.

[c14_rain_wind]

GUS Put it together and here's my call for Sydney. Storms are likely from this evening, easing again overnight.

GUS Rain with them should mostly be light to moderate, around 2 millimetres on average, this is a storm day, not a soaking day.

GUS The main risks are hail, maybe large enough to dent a car, gusty wind, and lightning, not flooding rain.

GUS If you're out tonight, keep half an eye on the sky, and bring the washing in and park under cover if you can.

GUS That's about four point seven million people who could see a storm tonight, so it's worth a simple plan.

[c14_rain_wind]

GUS Down in Melbourne, more rain, Victoria's really earning its nickname this week.

GUS Today's top is 21.7 degrees, after heavy showers through the morning, with about 6 millimetres of rain and counting already down.

GUS Tomorrow is milder and showery too, a low of 8 degrees and a high of 18 degrees, with another 8 millimetres of rain or so likely.

GUS If you're heading to Sandown for the Supercars this weekend, pack a jacket, more on that later.

[c16_temp]

GUS Up in Brisbane, it's steamy and dry, the kind of day that makes you grateful for air conditioning and iced coffee.

GUS No rain on the cards and no storm risk either today or tomorrow.

GUS Today's top is 31.8 degrees, climbing to 33.7 degrees tomorrow, properly warm for early November.

GUS The ground here is still on the wet side from recent rain, so it won't take much for the parks and gardens to up again.

[c16_temp]

GUS Across in Perth, same old same old, sunshine, clear skies, and probably a smug coffee in hand.

GUS Today's top is 24.6 degrees, easing only slightly to 25.1 degrees tomorrow, pretty pleasant for this time of year.

GUS Nothing on the radar or the satellite near Perth right now, so enjoy it.

[c12_index_map]

GUS Out off Hervey Bay and Bundaberg in Queensland, there's a pocket of strong storm energy building for Thursday afternoon.

GUS About 2200 joules of stored energy there, with decent wind shear too, so a few storms could turn out hail and squally wind.

GUS It's not locked in yet, the trigger is marginal, so keep an eye on the forecast rather than planning around it.

[c15_index_map]

GUS Now a genuine warning. As of 2:03 pm Brisbane time, the Bureau of Meteorology has an extreme heatwave warning out for the Kimberley and North Interior districts of Western Australia.

GUS South of Broome, inland, our models put the fire danger index at a reading of 87, which is in the extreme category, with ground that's been drying out for a long time.

GUS That drought factor, how much dry fuel is sitting on the ground, is about as high as it gets, close to 10 out of 10.

GUS Air temperatures in that area are forecast near 47 degrees, properly dangerous heat for anyone working or travelling through that country.

GUS For the official warning and any total fire bans, check bom.gov.au.

[c15_index_map]

GUS Also from the Bureau, there are now two severe heatwave warnings current for the Pilbara district of Western Australia.

GUS The first covers Karratha, Port Hedland and the mining towns around them, with daytime temperatures forecast to sit near 44 degrees for several days running,

GUS hot enough that anyone working outside needs regular water breaks and shade, and anyone without air conditioning checked on.

GUS The second covers the same district further inland around Newman and the mining country there,

GUS where overnight lows are only easing to about 29 degrees, giving bodies little chance to cool down before the heat builds again each day.

GUS For the latest on both warnings and any other alerts, check bom.gov.au.

[c16_temp]

GUS The Bureau also has a heatwave warning for the Daly, Arnhem and Carpentaria districts, inland from Darwin.

GUS Tomorrow is 35.2 degrees for the high with about 2 millimetres of rain likely as storms build to the south, more on that shortly.

[c07_cape]

GUS Storms are also possible right near Broome later today, with plenty of energy in the air.

GUS Broome is a coastal town, home to about 15,000 people, so it's worth keeping an eye on the sky there too.

[c16_temp]

GUS Over in Adelaide, it's mild, dry and quiet, no rain and no fire worries today or tomorrow.

GUS Today's top is 17.7 degrees, and tomorrow's a similar low of 10.7 degrees and high of 17.6 degrees.

GUS Good drying weather in Adelaide, so the washing's laughing while the rest of the country gets wet or hot.

[c20_town_table]

GUS Canberra gets a top of 21.6 degrees today, and tomorrow a chilly low of 6.6 degrees, a high of 21.2 degrees and a touch of rain, about 1 millimetre.

GUS Hobart's top today is 16.3 degrees, and tomorrow's cooler again, a low of 11 degrees and a high of 18.4 degrees, with a decent 8.6 millimetres of rain likely.

GUS That's actually the wettest signal among the capitals tomorrow outside Sydney, so keep a coat handy down south.

[c10_sim_radar]

GUS Looking ahead to tomorrow, Thursday, the biggest storm energy in the country sits across the Top End and Gulf Country.

GUS First, Thursday afternoon, storms are likely near Normanton in Queensland's Gulf Country, with heavy rain, hail and damaging wind all possible.

GUS That storm signal sits in the north-west Northern Territory, about 120 kilometres south of Darwin, over cattle station country along the Stuart Highway.

GUS Then Thursday evening, the action shifts to just south of Darwin, where the supercell composite is genuinely huge.

GUS I don't say this often, but the supercell number there is about as high as it ever gets, close to the top of the scale used anywhere in the world.

GUS Later still, storms can also reach further east near Borroloola, overnight, as individual storms often join into one larger cluster as they move.

GUS Darwin itself is home to about 122,000 people, so that evening storm risk is one to watch, even though it's a day away.

[c18_model_compare]

GUS Three models feed this forecast, the American GFS, the European model, and the European AI model, and for the Darwin storm rain they mostly agree.

GUS Over the next two days the American and European AI models both point to 17 to 19 millimetres near that hotspot, the European model is drier, around 8 millimetres.

GUS When two models agree and one is the outlier, I lean towards the wetter pair, so I'm expecting a decent soaking there, not just a token shower.

[c92_river_gauges]

GUS The Bureau also has a moderate flood warning out for the Balonne River, from Surat down to Warkon, and also for the Barcoo River further west, both in southern and western Queensland.

GUS On the Balonne, the gauge at Weribone is at 4.44 metres and rising, with Dogwood Creek near Surat up to 2.32 metres and still climbing.

GUS On the Barcoo, the gauge at Isisford is 4.87 metres and rising, while further downstream at Coolagh it's actually started falling, 5.05 metres now.

GUS That affects Isisford and Barcoo River communities including around Blackall, home to a bit over a thousand people, so check bom.gov.au for the detail.

GUS Elsewhere, nothing like flood levels, but the Grose River near Sydney is up to 1.05 metres and rising.

GUS Those are both just reflecting today's rain, not a flood risk, I'm simply keeping an eye on rivers right across the country, not just in Queensland.

[c15_index_map]

GUS One more warning from the Bureau, this one covering the Peninsula, the Gulf Country and parts of inland Queensland, including around Flinders.

GUS That's hot, dry country already, so take it seriously if you're travelling or working out there, water and shade matter.

[c06_pwat]

GUS One more thing worth knowing, the ground under south-east Queensland is already very wet, based on rainfall records from SILO, the Queensland Government's climate database.

GUS About 20 millimetres has fallen there in the last week, well over what's usual, so new rain runs off faster than it soaks in.

[c90_events]

GUS A quick look at the weekend's big events and what the weather means for them.

GUS In Newcastle, Saturday's Rugby League World Cup semi-final could see about 8 millimetres of rain during the match, worth an umbrella if you're going.

GUS At Rosehill in Sydney for Everest Carnival Ladies Day, expect a few millimetres of rain and breezy conditions, pack a coat as well as your fascinator.

GUS Down at Sandown for the Supercars meeting in Melbourne, there's a touch of rain forecast but nothing that should trouble the racing.

GUS Everything else this week, from the Foo Fighters in Brisbane and Sydney to the Melbourne Cup carnival at Flemington, looks weather kind.

[c20_town_table]

GUS Now the week ahead, using a European model's nine-day outlook. This is a rain and temperature signal only, nothing about thunderstorms or hail.

GUS Confidence is good for the next two or three days, a reasonable guide four to five days out, and only a rough signal by days six to eight.

GUS South-east Queensland sees little rain through Thursday and Friday, then showers return by the weekend, Gympie the wettest at around 6 millimetres.

GUS Central Queensland picks up showers Saturday through Monday, Gladstone and Rockhampton the wettest, while northern New South Wales gets a heavier burst, Newcastle near 15 millimetres Saturday.

GUS Victoria and Tasmania are the wettest corner again this Saturday, with Melbourne likely well over 15 millimetres.

GUS Darwin and Katherine both stay wet most days as the build-up season rolls on.

[c20_town_table]

GUS So the weekend verdict for the big population centres. South-east Queensland looks mostly dry through Friday, with showers returning by Saturday, nothing severe flagged yet.

GUS Sydney looks showery and unsettled through the weekend, keep an eye on Saturday in particular.

GUS Canberra looks mostly dry and cool, with just a touch of rain possible.

GUS Melbourne is the one to watch, heavy rain is likely Saturday, with 15 to 20 millimetres possible.

[c07_cape]

GUS Looking further out using the American GFS model's storm ingredients, not a storm forecast, just the raw ingredients in the air.

GUS Saturday and Sunday, both south-east Queensland and the Top End have plenty of stored storm energy in the air, the same kind of energy we talked about with Sydney earlier.

GUS But there's no obvious trigger to set it off yet, so storms could easily fizzle instead of firing.

GUS North Queensland looks similar Saturday and Sunday, plenty of energy, an uncertain trigger.

GUS Confidence drops the further out we go, by day five or six this is only a rough signal, and the next bulletin will update it.

[c02_mslp_fronts]

GUS Overall my confidence in today's forecast is high, mostly because the models agree well on this weekend's rain.

GUS What would change my mind is if the European model's drier signal for the Top End storms turns out right instead of the wetter American and AI models.

[c06_radar_now]

GUS For all the official warnings, check bom.gov.au.

GUS My next bulletin is tomorrow morning.

GUS If you've got a weather question, pop it in the comments and I'll get to as many as I can during the day.

GUS And tell me what the sky's doing where you are right now, I like knowing what's actually happening out there.

GUS Here's your homework, watch how fast the clouds build over Melbourne tomorrow, the tell-tale sign of Saturday's rain arriving early.

GUS Look up now and then, the sky's the best show in town.

GUS Gus's Weather is a PandaVision production.