Severe storms for Wagga and Lismore | Australia weather Sat 31 Oct morning | Gus's Weather

Severe storms for Wagga and Lismore, catastrophic fire risk SA - Sat 31 Oct

[c06_radar_now]

GUS G'day, I'm Gus, and this is your Gus's Weather morning bulletin for Saturday the 31st of October.

GUS The big story today: severe storms for inland southern New South Wales and Canberra tonight, then north-east New South Wales on Sunday.

GUS It's about 6 am in Brisbane at the time this is uploaded.

GUS This is the Bureau of Meteorology's real national radar, the actual measured picture, not a model, and the newest sweep is only a few minutes old.

GUS The heaviest rain in the country is out near Kununurra in Western Australia, a very heavy patch over cattle station country, and the model's simulated radar has it in much the same place.

GUS Closer to people, there's heavy rain near Airlie Beach and the Sunshine Coast in Queensland, moderate rain near Kingaroy, and a very heavy burst near Hughenden, plus heavy rain north-west of Warrnambool in Victoria.

GUS Among the capitals, Brisbane and Canberra both have heavy rain, Sydney and Perth have rain, Adelaide, Melbourne and Hobart have light rain, and Darwin is clear.

GUS Tell me in the comments what the sky's doing where you are this morning, I do read them through the day.

[c05_obs_now]

GUS Right, let's check the Bureau's actual rain gauges, always worth a look before trusting any model.

GUS A millimetre of rain is how deep the water would be if it collected in a gauge: a few millimetres is a sprinkle, 25 millimetres is a proper drenching.

GUS Charleville in Queensland is the wettest spot in the country since 9 this morning with 52.8 millimetres of rain, and the strongest gusts in the country, 85 kilometres an hour, were in Victoria's high country.

GUS It's raining right now at Townsville in Queensland, with gusty bursts.

GUS That's all measured by Bureau of Meteorology weather stations, credit to them for the data.

[c07_lightning_now]

GUS We also track lightning now, using the Blitzortung network, a volunteer lightning detection system, and it's a nice early warning of where storms are actually firing.

GUS The busiest cluster is still over Hughenden in Queensland, with about 300 strikes in the last six hours and holding steady.

GUS Smaller, quieter clusters sit further inland, including near Kununurra and out at sea west of Darwin.

GUS This is a sample of strikes, not a full count, so I'll never give you an exact total, just where it's active and whether it's growing or easing.

[c04_satellite]

GUS Satellite measures how cold, and so how high, a storm's top is, which tells us how strong it really is, and it can see areas the radar can't reach.

GUS The coldest storm top in the country is out near Kununurra in Western Australia, minus 77 degrees Celsius, a genuinely powerful storm over cattle station country.

GUS On the satellite loop, Brisbane, Melbourne, Hobart and Darwin have deep, cold storm cloud nearby, while Sydney, Adelaide, Perth and Canberra are clear of it.

GUS So the headline for today: severe thunderstorms for inland southern New South Wales and the Top End tonight, then north-east New South Wales on Sunday, alongside catastrophic fire danger in South Australia.

GUS For the weekend verdict: Canberra and inland southern New South Wales see storms likely tonight, Sydney and Melbourne stay largely clear of this system, Brisbane just sees periods of rain, and Sunday near Lismore is the day to watch in the north-east.

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

[c01_verification]

GUS Before I tell you what's coming, it's only fair to check how I went yesterday.

GUS Across 46 towns my daytime highs were off by an average of 1.8 degrees, with a small cool bias, and Perth was my worst miss, 6.6 degrees under what actually happened.

GUS My rain calls were mostly right, but I missed rain that didn't show up at Cairns, Coober Pedy, Darwin, Esperance and Longreach, so treat isolated rain calls with a bit of healthy doubt.

[c02_mslp_fronts]

GUS Here's the big picture, the pressure pattern across the whole country, think of the lines like contours on a map, except they're joining up places with equal air pressure, and tightly packed lines mean stronger wind.

GUS There's a high building over eastern South Australia near Whyalla, 1018 hectopascals, that's the lazy old fellow keeping things settled behind it.

GUS A low sits over the Nullarbor in Western Australia, with another near Mount Isa in Queensland.

GUS High above, the jet stream, a fast ribbon of wind near the top of the atmosphere, like a conveyor belt steering and energising the weather underneath it, is running near 300 kilometres an hour out over the Indian Ocean.

GUS There's something quietly amazing about that: a river of wind moving faster than a Formula One car, thousands of kilometres from anywhere, and the southern edge of it is what's dragging energy and spin across inland New South Wales and the Top End.

GUS That combination, warm moist air at the surface and a disturbance aloft, is exactly the recipe for tonight's storms.

[c08_skewt]

GUS This is a model sounding, a core sample through the air, showing how temperature and moisture change with height.

GUS About 50 kilometres south of Lismore, stored storm energy is about 1568 joules per kilogram, plenty to build tall storms by Sunday afternoon.

GUS The cap is weak, moisture is plentiful, and downdraft energy near 1078 joules per kilogram can drive damaging wind gusts.

[c11_shear]

GUS Wind shear is how much wind changes speed and direction with height, like cars in different lanes moving at different speeds.

GUS Here it's about 83 kilometres an hour through six kilometres of air, strong enough for a storm that can start to spin.

GUS That supports large hail and damaging wind as the main risks by Sunday afternoon.

[c07_cape]

GUS The other storm area is south-west of Canberra near Wagga Wagga, firing earlier tonight around 5 pm local.

GUS There's a bit less of that stored storm energy here, about 1171 joules per kilogram, but the wind shear is even stronger, about 103 kilometres an hour through six kilometres of air.

GUS That stronger shear pushes the supercell value up to a similarly high level here, and the rotation value is even higher, a strong value, so a rotating storm is a real possibility tonight.

GUS This air is drier higher up, which favours strong downdraughts, so damaging wind gusts and large hail are the headline risks here, not so much tropical-style heavy rain.

GUS Canberra itself sits just north-east of this, and its own forecast already shows rain and gusts to 56 kilometres an hour tonight.

[c14_rain_wind]

GUS Let's run through today's storms in the order they actually arrive, earliest first.

GUS First, tonight, inland near Wagga Wagga: thunderstorms with hail, damaging wind and heavy rain all possible.

GUS Storms with hail and damaging wind also threaten the Top End near Kununurra tonight.

GUS Storms can join into one bigger cluster overnight, think of separate cells merging like cars bunching into a traffic jam, with heavier pockets embedded inside it, which is why one town gets hammered and the next gets almost nothing.

GUS Sunday afternoon, the same risk shifts to north-east New South Wales.

GUS Sunday evening also brings a chance of storms over the Gulf Country in Queensland, around towns like Normanton and Burketown, and inland south-east Queensland near Roma, both out where people live around stations, highways and small towns, but with less dramatic numbers than the main two areas.

GUS Nearer the coast around all these systems it's more luck of the draw, patchy showers for some, nothing for others, so don't lock in exact rain totals, just expect the chance.

[c19_plume]

GUS I always check more than one model before I commit to a number, because no single model gets it right every time.

GUS There, the American GFS, the European model and the European AI model cluster around 4 to 8 millimetres of rain over the next two days.

GUS Near Wagga Wagga, all three agree closely on about 7 to 9 millimetres tonight, then almost nothing tomorrow once the storms move through, that's a strong agreement, over 90 per cent.

GUS Those are area averages though. Individual storm cells can dump far more than that in a short burst, some spots near these systems could see rain rates over 20 millimetres an hour under the heaviest cells.

GUS I'm leaning toward the models' own ensemble figure rather than the single wettest run, so patchy totals in that 5 to 10 millimetre range away from the storm cores, with isolated heavier falls right under them.

[c15_index_map]

GUS This next one isn't a joke, so let's be plain and careful here.

GUS Forecasters use a fire danger index that blends heat, wind, dryness and how much dry fuel is around, to say how dangerous a fire would be if one started.

GUS About 40 kilometres south-west of Coober Pedy in northern South Australia, that index reaches an extreme level on Sunday evening, which is catastrophic, the worst category there is.

GUS The ground there has been drying for a long time, the Bureau's drought factor measure, built from actual rainfall history, is right near the top of its scale, about as dry as it gets.

GUS Coober Pedy is home to about 1,400 people, and this country also has mining operations, stations and a highway running through it, all exposed if a fire starts in these conditions.

GUS In catastrophic conditions a fire can be unpredictable and extremely dangerous, so please check total fire ban notices and official advice at bom.gov.au.

[c92_river_gauges]

GUS The Bureau of Meteorology has an Extreme Heatwave Warning for the Tiwi District and a Severe Heatwave Warning for the Arnhem District, both near Darwin, as of 4:36 am Brisbane time.

GUS There's also a Major Flood Warning for the Condamine River downstream of Oakey Creek to Cotswold, where levels are sitting above 8 metres in places.

GUS The Bureau also has a Severe Heatwave Warning for the Peninsula and Gulf Country districts in far north Queensland, where afternoon temperatures are expected to reach about 41 degrees for several days in a row.

GUS On top of those, there's a Moderate Flood Warning for the Bulloo River to Quilpie and at Quilpie itself, with the river forecast to peak around 4.5 metres in the next day or two, plus Moderate Flood Warnings for the Condamine River downstream of Warwick to Oakey Creek and the Warrego River downstream of Charleville.

GUS Looking at the rivers the Queensland Government measures, the Logan River at Yarrahappini is at 2.8 metres and falling, the Mary River at Miva is at 3.3 metres and falling, and the Fitzroy River at The Gap is steady around 6.2 metres.

GUS Ground in south-east Queensland and northern New South Wales is already very wet from recent rain, so fresh rain there runs off faster and rivers can rise quicker than the rainfall alone suggests, credit to SILO and the Queensland Government for that rain history.

GUS I never put a flood category on these river numbers myself, that call belongs to the Bureau, so for all the official warnings check bom.gov.au.

[c90_events]

GUS A few big outdoor events to flag for today and tomorrow.

GUS Sydney has big events this weekend, including Sculpture by the Sea, with a thunderstorm risk and gusts near 49 kilometres an hour.

GUS In Melbourne, Derby Day at Flemington, around 86,000 people expected, also has a thunderstorm risk with similar gusts, so pack a coat with the fascinator.

GUS Perth's Halloween event at Wellington Square should get a couple of millimetres of rain but a lower storm risk.

GUS If you're at any of these, keep an eye on the sky, lightning means play or performances stop, and always follow what the organisers tell you to do.

[c16_temp]

GUS Darwin itself sits around a top of 31 this weekend, but the country around it is a different story.

GUS Those heatwave warnings near Darwin mean several days of dangerous heat stacking up, harder on the body than one hot day.

GUS Inland, the hottest reading today is about 43 degrees east of Darwin.

GUS This is the build-up season up north, when trade winds swing around, humidity climbs, and monsoon rain doesn't arrive until December.

GUS In a heatwave, check on anyone elderly or unwell, and drink plenty of water, that's not a joke, it's just good sense.

[c20_town_table]

GUS Right, here's every capital, today's daytime high, and tomorrow's overnight low and daytime high, plus the rain for each day.

GUS Brisbane: today's high 24 degrees, tomorrow's low 18 degrees and high 28 degrees, with basically no rain either day, nothing to worry about.

GUS Sydney: today's high 28 with no rain, tomorrow's low 20 and high 24, with about 2 millimetres of rain, worth an umbrella in the bag.

GUS Melbourne: today's high 23 degrees with about 2 millimetres of rain, tomorrow's low 11 degrees and high 20 degrees, with a soggier 5 millimetres, pack a coat.

GUS Why did the cold front break up with the high pressure system? It just couldn't handle the pressure. Sorry, not sorry, back to the forecast.

GUS Canberra: today's high 24 with storms tonight, tomorrow's low 10 and high 23, with about 6 millimetres of rain.

GUS Hobart: today's high 19 degrees with no rain, tomorrow's low 12 degrees and high 17 degrees, with about 5 millimetres, that's a jumper-and-a-cuppa start to Sunday.

GUS Adelaide: today's high 19 degrees with about 5 millimetres of rain, tomorrow's low 13 degrees and high 25 degrees, drying out nicely, the washing will finally get a go.

GUS Perth: today's high 22 degrees with a decent 5 millimetres of rain, the garden will love that, tomorrow's low 15 degrees and high 20 degrees with another 3 millimetres, take an umbrella.

GUS Darwin: today's high 34 with about 7 millimetres of rain, tomorrow's low 26 and high 34 with 4 millimetres, typical build-up weather.

[c18_model_compare]

GUS Now let's look further out, days two through eight, using a European model's longer range rain signal. It's rain only, it carries no thunderstorm or hail information, so it can say wet, never storms.

GUS South-east Queensland, Sydney, Canberra and Melbourne stick with the rain and storm chances from the capitals roundup.

GUS Looking further out, south-east Queensland gets another shower signal on Tuesday, then turns quieter through the week. The stored storm energy returns there Tuesday with little obvious trigger, so that's worth watching but don't lock it in.

GUS Northern New South Wales shows a genuinely wet signal Sunday, with both plenty of storm energy and a trough to set it off arriving Tuesday, a stronger setup worth watching.

GUS Victoria and Tasmania get a proper soaking Monday and again Wednesday next week, both models agree it's wet, Melbourne, Geelong, Ballarat and Bendigo all in for it.

GUS The Top End keeps firing most days this week, with the models disagreeing on exactly where the storms land.

GUS What do you call a thunderstorm that's brilliant at maths? A calcul-rain-tor. I'll see myself out.

GUS Days two and three here are a reasonable guide, days four and five more of a rough guide, and day six onward is only a signal that can flip completely by the next bulletin, because tiny errors in a model grow larger every day.

[c20_town_table]

GUS My overall confidence in today's call is high today, mostly because the models agree closely on rainfall amounts and on where that low pressure system sits.

GUS Where I'm less certain is exactly where the heaviest hail and wind fall within these storm bands, which can shift by tens of kilometres at short notice.

GUS Here's your homework: this afternoon, watch for tall, anvil-shaped cloud tops building to the west, a sign a storm is maturing before it reaches you.

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

GUS My next bulletin is this afternoon, so 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, and if you want these every morning and afternoon, subscribe.

GUS Thanks for watching, I appreciate you starting your Saturday with me.

GUS Gus's Weather is a PandaVision production.