Storms build for inland Qld, NSW and Vic; | Australia weather Fri 30 Oct morning | Gus's Weather

Storms build for inland Qld, NSW and Vic; heatwave up north

[c06_radar_now]

GUS G'day, I'm Gus. This is your Gus's Weather morning bulletin for Friday the 30th of October, and it's about 6 am in Brisbane at the time this is uploaded.

GUS Severe storms are lining up for inland Queensland, New South Wales and Victoria from tonight into the weekend, and a severe heatwave is building over the Top End and Cape York.

GUS This is the Bureau of Meteorology's own national radar, the real measurement, not a model guess, and the newest sweep is only 2 minutes old.

GUS The heaviest patch on the continent is a heavy cell just north of Ceduna in South Australia, about 9,000 square kilometres, with another heavy cell 247 kilometres south west of Townsville.

GUS A very heavy, intense cell sits just 48 kilometres east of Darwin itself, smaller at about 690 square kilometres but right on a capital city's doorstep.

GUS Of the eight capitals, Darwin has heavy rain, Perth has rain, and Adelaide, Canberra and Brisbane have a touch of light rain about.

GUS Sydney, Melbourne and Hobart are clear on the radar, and a model picture for this hour broadly matched what that real radar is showing.

GUS The big story today is storms building inland over the next two days, plus fire and heat risk up north. Everything here is indexed in the description, so jump to the chapters if you're in a hurry.

[c07_lightning_now]

GUS Lightning across the country in the last six hours, from the Blitzortung lightning network of volunteer ground sensors, which catches strikes even where radar coverage is thin.

GUS That same cell near Ceduna is also the busiest lightning spot in the country, over 900 strikes in the last six hours, though it's easing now, out over remote country.

GUS Smaller clusters are easing near Alice Springs and south of Hughenden, while one near Yulara is growing, about 150 strikes in the last hour, in tourist country near Uluru.

GUS Over 2,000 strikes nationwide in six hours, mostly inland, nothing threatening near a capital city.

[c05_obs_now]

GUS Here's what's actually fallen since 9 this morning, measured at Bureau of Meteorology weather stations, not a forecast.

GUS Hughenden in Queensland leads with 44 millimetres of rain, a millimetre being how deep the water would sit in a gauge, so that's a solid drenching.

GUS Ernabella in South Australia and Yulara in the Northern Territory have both had 41 millimetres, Wadeye in the Territory 36 millimetres, and Cloncurry in Queensland 28 millimetres.

GUS The strongest gusts anywhere this morning, around 50 to 54 kilometres an hour, were at remote stations down in Tasmania's far south. That's all rain already fallen, credited to the Bureau of Meteorology.

[c04_satellite]

GUS Now the satellite, because it measures how cold, and therefore how high, storm tops are, which tells us how strong a storm really is, and it sees where radar can't.

GUS The coldest, tallest storm cloud right now is out over the Indian Ocean, colder than minus 74 degrees Celsius at the top, a long way north west of Broome, over open water.

GUS There's also deep storm cloud right over Darwin, matching the heavy rain already on radar there, though the model's own radar missed that storm, so trust the satellite and the real radar over the model this morning.

[c01_verification]

GUS Quick check on yesterday's call first, since that tells you how far to trust today's forecast.

GUS My overnight lows were spot on in Adelaide, Darwin and Sydney, close elsewhere except Perth which ran about 3 degrees too mild, and nationally my daytime highs were off by less than 2 degrees on average, so confidence today is reasonably good.

[c02_mslp_fronts]

GUS Let's look at the big picture, because the pressure pattern explains both today's fire risk and the storms building for the weekend.

GUS A high of 1027 hectopascals, a measure of air pressure, sits near Coffs Harbour in northern New South Wales, and a low of 1006 hectopascals is parked over the Nullarbor in Western Australia.

GUS In between, a long trough, a stretched out line of lower pressure that lifts air and can set off storms and rain, runs from the Coral Sea east of Brisbane down into northern New South Wales, dragging in warm moist air that digs out instability right across inland Queensland, New South Wales and Victoria over the next two days.

GUS The Bureau of Meteorology has a major flood warning out for the Condamine River downstream of Oakey Creek to Cotswold in southern Queensland, with the river near 8 metres this morning.

GUS There's also a moderate flood warning for the Warrego River downstream of Charleville and at Bakers Bend, sitting around 4 metres and rising slowly.

GUS And a moderate flood warning for the Weir River downstream of Giddi Giddi South and at Talwood, near 3 metres this morning, all as of 5:19 this morning.

GUS Around Brisbane and south east Queensland the ground is already very wet, about 105 millimetres of rain in the last week, more than six times normal, measured using SILO data from the Queensland Government, so new rain runs off faster into those rivers.

GUS On the gauges themselves, the Logan River at Yarrahappini and the Mary River at Miva are both falling, while the Fitzroy River at The Gap has been slowly rising to 6.3 metres; none of that is a flood call, that belongs to the Bureau.

GUS There's a severe heatwave warning current for the Tiwi and Arnhem districts in the Northern Territory, with little overnight relief below the high twenties.

GUS And a separate severe heatwave warning for the Peninsula and Gulf Country in far north Queensland, with afternoon temperatures near 40 expected to continue into the weekend.

GUS For the exact towns and rivers covered, the official warnings are at bom.gov.au.

[c07_cape]

GUS Now let's build the storm forecast from the ground up, starting with fuel, because a storm needs energy to grow tall, the way a car needs petrol.

GUS Meteorologists measure that stored energy in the air and call it CAPE, in joules per kilogram. The higher the number, the more energy is sitting there to build a storm.

GUS In southern Victoria near Sale there's about 1,150 joules per kilogram, in southern Queensland south east of Longreach about 810, and in central New South Wales near Dubbo also about 810, a solid tank for this time of year at every one of them.

GUS None of that guarantees a storm by itself, it just means the ingredients are sitting there waiting for something to set them off, which is what we look at next.

[c11_shear]

GUS At those same hotspots, let's check the lid. Warm air sits above the ground like a lid on a pot and stops rising air breaking through, until something lifts it or burns it off.

GUS Over Sale in Victoria that lid is basically gone, so storms can fire easily there this afternoon, with wind shear around 91 kilometres an hour, a supercell value of about 7.

GUS Near Dubbo the shear reaches about 114 kilometres an hour, with a supercell value of about 3.

GUS A supercell is a thunderstorm with a long lived, rotating updraft, like a spinning top the storm manages to stand upright, and it's the storm type that can produce large hail and damaging wind. The hail signal isn't lit up strongly in today's numbers, so rotation and damaging wind look like the bigger risk here, more than giant hail.

[c10_sim_radar]

GUS Let's take the hazards in the order they'll actually arrive, starting tonight and running through the weekend. This afternoon it's mostly a fire and heat story over inland South Australia, covered shortly.

GUS Tonight, storms fire south east of Longreach in southern Queensland near Blackall, home to just over a thousand people, bringing hail, damaging wind and heavy rain through the evening.

GUS The models agree closely there, a reliable rain signal, nothing dramatic. Keep an eye on the evening sky out that way; the next bulletin will update the totals.

[c10_sim_radar]

GUS Saturday is the bigger day, with storms expected over Victoria by early afternoon and near Dubbo by early evening.

GUS Think of it as two zones. Right where the trigger meets the moist, unstable air, storms can be strongest, large hail, damaging wind gusts and heavy rain. Closer to the coast it's patchier, some towns get soaked, others miss out entirely, just luck of the draw.

GUS Gippsland in Victoria is in the strong zone Saturday afternoon, Dubbo and Orange in New South Wales that evening, and the country's strongest reading, a supercell value of about 8, sits just west of Canberra around 5 pm.

GUS Overnight, these separate storms can join into one bigger cluster, forecasters call it a mesoscale convective system, which can drift toward the coast, so don't be surprised if a coastal town gets a late storm that wasn't obviously in the firing line during the day.

GUS Melbourne could catch the edge of Saturday's activity too, with a bit of rain moving through.

GUS None of this is locked in yet, the placement is the uncertain part even when the energy is fairly well agreed on, so check back this afternoon for an update.

[c15_index_map]

GUS Now the other big story today, fire danger, because dry fuel and strong, hot wind can make a fire very hard to control.

GUS Forecasters use an index called the Forest Fire Danger Index, which rolls temperature, wind, dryness and fuel together into one number.

GUS Today South Australia's worst reading, about 66, rated severe, sits north of Coober Pedy, driven by heat, dry air and gusty wind.

GUS Further west, inland Western Australia's Gibson Desert is running even higher, an extreme reading, but that's country with stations, mines and the highway rather than towns, so the real risk there is to travellers and livestock, not a population centre.

GUS If you're travelling that stretch of highway today, keep an eye on fire information for South Australia, and remember all official warnings are on bom.gov.au.

[c94_sounding_compare]

GUS Here's a core sample straight up through the atmosphere at two spots, one in Victoria and one in Queensland. The line on the right is air temperature, the line on the left is dew point, a measure of moisture; where they sit close together the air is nearly saturated.

GUS Over Victoria that moist layer reaches up to about 300 hectopascals, over Queensland about 350, a lower number meaning deeper moisture, so both have enough depth to support heavy rain, not just a sprinkle.

GUS This is a model's best guess at the atmosphere, not an actual weather balloon, so treat it as a guide.

[c18_model_compare]

GUS How much do the American GFS, the European model and the European AI model agree on today's rain? Near Longreach the three models agree closely, about 21 to 24 millimetres, a reliable signal.

GUS Over Victoria the models spread out more, from almost nothing to about 9 millimetres, so I'm leaning toward the lighter, patchier end of that range.

GUS Near Coober Pedy the models disagree a lot on rain, so treat that number loosely. The energy is fairly well agreed on, but exactly where and how much it rains is the uncertain part.

[c20_town_table]

GUS Let's do the lap of the capitals: today's high, tomorrow's low and high, and the rain, because someone has to tell Perth it is not always sunny there.

GUS Brisbane, a high today of 25, little to no rain. Overnight down to 16, then 26 tomorrow with next to no rain again, nothing to worry about.

GUS Sydney, a high today of 23 and dry. Overnight down to 14, then up to 27 tomorrow, still dry, good washing weather.

GUS Melbourne, a high today of 26 and basically dry. Overnight down to 8, then 24 tomorrow with a bit of rain, about 1 millimetre, enough to dampen the barbecue plans but not ruin them.

GUS Perth, a high today of 22 with a touch of rain. Overnight to 16, then 22 tomorrow with a more decent soaking, around 8 millimetres, worth having an umbrella handy.

GUS Adelaide, a high today of 25 and dry. Overnight to 17, then down to 20 tomorrow with about 5 millimetres of rain.

GUS Canberra, a high today of 25 and dry, overnight to 7. Hobart, a high today of 21 and dry, with no rain expected, overnight down to 7.

GUS Darwin, a high today of 33 with a bit of rain under that heatwave warning, overnight down to 26; typical build up weather, hot and sticky.

[c90_events]

GUS Quick look at the week's big events, because weather can make or break a crowd day.

GUS Saturday's Victoria Derby Day at Flemington in Melbourne has the biggest weather signal, a supercell value of about 3, a modest reading, near the track, gusts to 60 kilometres an hour and a good chance of thunderstorms, so have a plan for when play pauses for lightning.

GUS Sydney has a busy weekend too: Sculpture by the Sea opens Friday on the Bondi to Tamarama walk with about 450,000 visitors expected, and Saturday's Golden Eagle Day and Halloween Festival both carry a chance of thunderstorms and a few millimetres of rain, so take an umbrella.

[c20_town_table]

GUS Now the week ahead, days two through eight, and fair warning Queenslanders, there's a decent dose of rain pencilled in for next week. This comes from a European model's nine day rain forecast, and it only tells us about rain, not thunderstorms or hail, so it can say wet, never storms.

GUS In south east Queensland, Tuesday the 3rd of November looks wettest, Toowoomba around 15 millimetres, with Brisbane and the coast picking up a few millimetres too.

GUS In Victoria and Tasmania, Monday the 2nd of November looks heaviest, Bendigo around 29 millimetres, with Melbourne, Geelong and Ballarat all catching some of it too, good news if you've been waiting to fill the water tank.

GUS Over the Top End, Sunday looks wettest, Darwin around 17 millimetres, part of the build up to the wet season. In the south west of Western Australia, tomorrow Saturday is the wettest day, Bunbury around 19 millimetres and Perth getting a decent share too.

GUS Days two and three are fairly reliable, days four and five more of a guide, and from day six onward it's only a signal that can change completely by the next bulletin, so treat anything that far out loosely.

GUS For the weekend: south east Queensland looks dry and settled, Sydney dry Saturday with a shower chance Sunday, Canberra watching that storm signal to its west Saturday evening, and Melbourne catching a possible shower or storm Saturday afternoon.

[c18_model_compare]

GUS Looking further out, days three to seven, using the ingredients only, not a storm guarantee.

GUS Monday the 2nd of November, south east Queensland and north Queensland both have what I'd call storm fuel with nothing to set it off, plenty of that stored storm energy we looked at earlier but nothing obvious yet to set it off, so storms could easily fizzle.

GUS Tuesday the 3rd looks more interesting: northern New South Wales has storm fuel with a trigger to set it off, energy plus a trough arriving to trigger it, and both the American and European models agree it gets wet. North Queensland carries that same storm fuel with nothing to set it off pattern that day; south east Queensland's Tuesday rain is the wet signal we already covered in the week ahead.

GUS Wednesday the 4th, confidence drops further out, but south east Queensland, north Queensland and central Queensland still show that storm fuel with nothing to set it off pattern, energy without an obvious trigger, and the Top End carries the same pattern on top of the wet season build up rain we mentioned earlier.

GUS None of this is a promise of storms, it's a read of the ingredients, so worth watching, and I'll update it in every bulletin as the picture firms up.

[c17_ens_prob]

GUS So how confident am I in today's call overall? I'd call it high confidence, comfortably in the upper part of my scale.

GUS That's built on the models broadly agreeing on the position of the weekend's storm troughs and the low pressure systems moving through the south, though they disagree more on exact rain totals in a few spots.

GUS What would change my mind: if the trigger over inland New South Wales and Victoria weakens or shifts track, the storm risk there could ease or move to a different corridor of towns. I'll know more by this afternoon's bulletin.

[c06_radar_now]

GUS That's the picture for Friday the 30th of October: storm energy building across the inland ahead of a big storm weekend, fire danger over parts of South Australia and Western Australia, and heatwave warnings in the north.

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

GUS I'm back again this afternoon with the next bulletin.

GUS If you've got a weather question, or you're seeing rain, hail or wind where you are right now, pop it in the comments and I'll get to as many as I can today. Thanks for watching, and if you haven't already, consider subscribing.

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