NSW Storm Warning, QLD Flooding & SA Fire | Australia weather Sat 31 Oct afternoon | Gus's Weather

NSW Storm Warning, QLD Flooding & SA Fire Danger - Sat 31 Oct

[c06_radar_now]

GUS G'day, I'm Gus, and this is your afternoon bulletin for Saturday the thirty first of October.

GUS The biggest story this afternoon is severe weather right across the country: a severe thunderstorm warning for inland New South Wales, major flooding on Queensland's Condamine River, and catastrophic fire danger in outback South Australia.

GUS It's about 4 pm in Brisbane at the time this is uploaded.

GUS If you're seeing hail, heavy rain or wind right where you are this afternoon, pop it in the comments, I'd love to know.

GUS Let's start with the Bureau of Meteorology's real national radar, not a computer model, this is the actual rain being measured, and the picture is about ten minutes old.

GUS The heaviest cell on the continent, top of the Bureau's scale, sits about 106 kilometres south east of Kununurra. There's very heavy rain near Forbes and Albany, top of the scale near Nowra, and heavy rain near Bairnsdale and Dubbo.

GUS Looking at the capitals, Sydney and Canberra both have heavy rain on the radar right now, so does Darwin, Hobart has rain, Brisbane and Perth just light rain, while Adelaide and Melbourne are clear.

GUS Our model had some of today's cells roughly right, but missed the big one near Kununurra. Everything in this bulletin is indexed in the description, so you can jump straight to the part you want from the chapters down there.

[c04_satellite]

GUS Now the satellite. Radar only sees rain that's already falling, but the satellite measures how cold, and therefore how high, a storm's top is, which tells us how strong a storm really is.

GUS The biggest storm on the satellite is inland of Kununurra, with a cloud top down to minus 87 degrees Celsius, colder than it ever gets at the South Pole.

GUS That one storm covers about 71,000 square kilometres, roughly the size of Tasmania, built entirely of ice flung twelve kilometres into the sky.

GUS Cloud tops that cold usually mean a storm is punching hard into the upper atmosphere.

GUS That's the kind of detail only the satellite gives you, radar shows rain, the satellite shows how fierce the storm is.

[c07_lightning_now]

GUS We're also tracking lightning now, across the whole country, using the Blitzortung lightning network, a volunteer detection system.

GUS The busiest cluster in the last six hours is out to sea, about 73 kilometres south east of Nowra in New South Wales, with well over 2,000 strikes picked up.

GUS There's a growing cluster near Melbourne too, about 35 kilometres north of the city.

GUS Canberra has had lightning nearby in the last six hours as well, and lightning across the country overall is growing this hour, not easing.

GUS This feed is a sample of strikes, not an exact count, so I'll never give you a hard total, just where it's busy and whether it's building.

[c05_obs_now]

GUS Here's what's actually been measured falling since nine o'clock this morning at Bureau of Meteorology weather stations, not a forecast, the real thing.

GUS Tasmania's alpine country is the wettest in the nation, Mount Read has had 48 millimetres of rain since nine, and Luncheon Hill 22 millimetres.

GUS Victoria's high country also got 22 millimetres at Mount Buller and Eildon Fire Tower, and Cape Naturaliste in WA picked up nearly 21 millimetres.

GUS It's raining now at Parkes, almost 9 millimetres since nine, and around Trentham East in Victoria.

GUS The strongest gust measured anywhere today is a howling 93 kilometres an hour on top of kunanyi, Mount Wellington above Hobart. I'm a robot, I don't feel the cold, but even my circuits would rattle up there.

GUS Credit to the Bureau of Meteorology for all of that, it's the real, measured weather, not a guess.

[c92_river_gauges]

GUS As of 6:57 pm Brisbane time, the Bureau's most serious warning today is a Major Flood Warning for the Condamine River downstream of Oakey Creek, through to Chinchilla, in Queensland.

GUS There's also Moderate Flood Warnings for the Bulloo River at Quilpie, the Warrego River below Charleville, and the Barcoo River between Blackall and Isisford, for every detail go to bom.gov.au.

GUS Away from the warnings, Queensland's rivers are mostly easing, the Fitzroy River at The Gap is steady near 6.3 metres, while the Bremer, Logan and Mary Rivers in the south east are all falling after this week's rain.

GUS This feed only gives me the level and whether it's rising or falling, not flood categories, so for the official flood warning levels always check bom.gov.au.

GUS One more thing before any new rain falls, how wet the ground already is matters. Dry ground soaks rain up like a sponge, wet ground can't take any more and it runs straight off.

GUS Around Brisbane, the ground is already very wet, about 70 millimetres in the last week.

GUS It's a similar story near Coffs Harbour, nearly 130 millimetres in a week.

GUS That means any new rain from Sunday's storms is more likely to run off fast than soak in, especially for anyone near Brisbane's rivers or the creeks around Coffs Harbour, worth keeping an eye on local levels this weekend.

GUS Credit to the Queensland Government and SILO for the river and rainfall data.

[c02_mslp_fronts]

GUS Let's zoom out to the whole weather map. A high near 1018 hectopascals sits over the Great Victoria Desert in South Australia, keeping the centre settled.

GUS Out over the Indian Ocean south west of Perth there's a low, 1010 hectopascals, with an upper trough running south from it, that's the feature stirring up today's showers in the state's south west.

GUS There's also a weak low near Mount Isa and a broad low over Indonesia feeding moisture into today's storms.

GUS Up at jet stream height, there's a fast ribbon of wind over the Indian Ocean north west of Perth, blowing up to 288 kilometres an hour, the kind of energy that can help spin up weather systems underneath it.

[c03_upper_500]

GUS Because it's cyclone season, I check for tropical systems every bulletin, even when there's nothing happening close to home.

GUS Right now there's no official tropical cyclone anywhere near Australia from the Joint Typhoon Warning Centre, and no cyclone like low showing up in our own model either.

GUS The European ensemble is watching a cluster of thunderstorms out near the dateline, with some of its forecast runs suggesting it could eventually become a system, but it's a long way from Australia and nothing to worry about yet.

GUS I'll keep an eye on that one and let you know if it ever turns our way.

[c16_index_map]

GUS Northern Western Australia is sweating through a top of 42, about 250 kilometres south of Broome, part of why the Bureau has a Severe Heatwave Warning for the Kimberley and North Interior districts.

GUS The Bureau also has a Severe Heatwave Warning for the Peninsula and Gulf Country districts of Queensland.

GUS There's also a Severe Heatwave Warning for the Tiwi, Arnhem and Carpentaria districts near Darwin.

GUS Darwin's own top today is 30, and it's the hot, sticky nights with little recovery that make this a heatwave warning, so take care if you're older or outdoors, keep the fluids up, and check on anyone vulnerable through the build up.

GUS Meteorologists use a fire danger dial called the FFDI, think of it running from zero to over one hundred, combining heat, dryness, wind and how dry the bush already is.

GUS Near Coober Pedy in northern South Australia that dial is reading 112, category catastrophic, with a drought factor of 9.9 out of 10, meaning the ground there has barely a drop of moisture left.

GUS That's the highest fire danger reading in the country today. Listen for any total fire ban out there and follow it.

[c07_cape]

GUS Now let's look at why storms can get going at all. Meteorologists measure the energy a storm can feed on, think of it like the petrol in a storm's tank, and they call it CAPE.

GUS About 50 kilometres south of Lismore, that tank reads 1,715 joules per kilogram by Sunday afternoon, decent fuel for the season, with a weak cap a trough should break open.

GUS Fuel alone isn't enough, you also need something to light the match, forecasters call that lid the cap, like a lid on a pot stopping bubbles rising.

[c12_index_map]

GUS Wind matters too. If the wind blows a different speed and direction higher up than it does near the ground, that's called shear, and it can tilt a storm's updraft and get it spinning. There, shear is strong, about 93 kilometres an hour through the lowest six kilometres of air.

GUS Forecasters combine CAPE and shear into one number, a supercell index, reading about 6 there, which is high, meaning any storm that forms could start to rotate.

GUS A supercell can bring large hail and damaging wind, so that's worth keeping an eye on through Sunday afternoon.

GUS These indexes are guidance, not a guarantee of hail or damage.

[c15_rain_wind]

GUS Let's put the country's storm risk in order, earliest first, because that's genuinely how a forecaster reads a day like this.

GUS First, this evening inland of Kununurra in the Top End, thunderstorms with hail, damaging wind and heavy rain are likely over cattle country and the highway there.

GUS Overnight, a similar risk sits about 200 kilometres west of Tamworth in northern New South Wales, again over grazing country rather than towns.

GUS Sunday afternoon that same northern inland system fires up, and that's also when the Bureau's current Severe Thunderstorm Warning for damaging winds and large hail covers the Central Tablelands, North West Slopes and Plains, and Central West Slopes of New South Wales.

GUS Sunday evening the fire danger near Coober Pedy peaks, as we covered a moment ago.

GUS Monday morning there's also a thunderstorm risk over the Gulf Country near Normanton, and inland of Ballarat in western Victoria, both over farming districts.

GUS None of tonight's or tomorrow's storm risk sits directly over a capital city, which is the main reason this isn't a bigger story for most of you, but it's a real one if you're in those areas.

[c94_sounding_compare]

GUS Here's a trick forecasters use to compare how wet the atmosphere is in two places at once, think of it as a core sample through the air.

GUS The line on the right of a chart like this is the air temperature, the line on the left is the dew point, a measure of moisture. Where they sit close together the air is nearly saturated, where they're far apart it's dry.

GUS Over Kununurra, that moist layer reaches all the way up past 300 hectopascals, high in the atmosphere, basically top to bottom moist air, which is why those storms there got so tall today.

GUS Over that same northern New South Wales hotspot, the moist layer only reaches about 650 hectopascals, lower down, so there's fuel near the ground but a drier cap above it that needs breaking before storms take off.

GUS This is a model's best guess at the column of air, not an actual weather balloon, but it's a handy way to compare two places at a glance.

[c20_plume]

GUS Before I trust any of this, I check whether our different computer models agree. There, the American GFS, the European model and the European AI model all broadly agree on today, but spread out more by Sunday.

GUS For the 24 hours to Sunday afternoon, the American model has about 3.5 millimetres, the European model 4.1 millimetres, and the European AI model nearly 6 millimetres, so they agree on some rain, not exactly how much.

GUS None of the three models put more than about 10 millimetres down in that 50 kilometre square over the next two days, which tells me this is a few showers and a possible strong storm, not a widespread soaking.

GUS I'm leaning toward the lighter end of that range being closer to the mark, but it's not locked in yet, check back in the next bulletin.

[c90_events]

GUS If you've got plans this weekend, here's what the weather means for them. Sydney's Halloween Festival and the BIGBANG concert tonight carry a real lightning risk, with storm energy near 1,250 joules per kilogram building over the city.

GUS Sculpture by the Sea at Bondi, drawing around 450,000 people into Monday, also faces a thunderstorm risk, so have a shelter plan since play stops when lightning starts.

GUS Sunday's Rugby League World Cup games at Parramatta carry the same storm risk through the afternoon and evening.

GUS Melbourne's Cup Day on Tuesday looks wet rather than stormy, models give a 90 per cent chance of at least 5 millimetres, so fascinators will get damp.

[c21_town_table]

GUS Brisbane's high today was 24, tonight's low near 17, tomorrow's high 28 with a low of 17, and about 1.4 millimetres of rain, nothing to worry about, a normal Saturday for the washing and the barbecue.

GUS Sydney's top today was 28 degrees with about 1 millimetre of rain, tomorrow's low 19 and top 24, with just over 2 millimetres, worth an umbrella given tonight's storm risk, with the Halloween Festival and the BIGBANG concert sitting right under that storm energy we mentioned, so take a lightning plan if you're headed into the city.

GUS Melbourne's top today is 23 degrees with 4 millimetres down already, tomorrow's low 10 and top just 20, with another 5 millimetres likely, a jumper and brolly weekend for the footy, and with the cricket season just starting, pad up and pack a rain jacket too.

GUS Canberra reached 24 degrees today with a millimetre of rain, tomorrow's low is about 10 degrees and the top 23 degrees, with 6 millimetres forecast, a damp start to Sunday in the capital, grab an umbrella if you're heading to the markets.

[c21_town_table]

GUS Adelaide's top today was 18 degrees, tomorrow's low about 13 degrees and the top 23 degrees, with barely any rain, good drying weather, the washing will be laughing on the line.

GUS Perth reached 20 degrees today with about 2 millimetres of rain, tomorrow's low near 13 degrees and top of 20 degrees brings a similar light shower, nothing that'll spoil a Sunday barbecue, a classic Perth weekend, sunshine with just a token shower.

GUS Darwin's top today is 30, under that heatwave warning tomorrow's low stays near 27 with a top near 34 and about 4 millimetres of rain, the classic build up feel.

GUS Hobart's top today was 17 degrees with just over a millimetre of rain, tomorrow's low around 12 degrees and top of 17 degrees brings almost 4 millimetres, a jumper and a cuppa kind of day down there, good excuse to stay in and watch the footy on the couch.

[c21_town_table]

GUS Now the week ahead, using a nine day rain outlook from a European model, this signal only tells us about rain, nothing about thunderstorms or hail, so I'll choose my words carefully.

GUS In south east Queensland, Tuesday looks showery with up to about 11 millimetres at the Sunshine Coast, but the ingredients outlook flags plenty of stored storm energy and nothing obvious to set it off that day, what I'd call storm fuel with nothing to set it off, storms might just fizzle.

GUS Why don't troughs ever win at poker? Because forecasters can always read their tell. Sorry, not sorry, back to the forecast.

GUS Northern New South Wales has what I'd call storm fuel with a trigger to set it off by Tuesday, plenty of stored storm energy and a trough arriving to set it off, worth watching from Coffs Harbour to Tamworth.

GUS Central Queensland looks quiet for storms early in the week, but by next weekend the rain signal turns heavy, up to 23 millimetres at Bundaberg, with the models disagreeing on exact timing.

GUS Victoria and Tasmania have the wettest signal of the lot, with both rain models agreeing on over 27 millimetres for Melbourne and over 23 for Bendigo by Monday.

GUS Zooming out from today's specific numbers to the pattern through the week, here's my one line verdict for the big population centres: south east Queensland, storms possible with storm fuel with nothing to set it off Tuesday; Sydney, showers but no severe signal; Canberra, a showery Sunday; Melbourne, wetter than average through midweek, the one to watch. Days two and three of all this are a reasonable guide, by day five or six it's only a signal that can flip in the next computer run. None of it looks like trouble getting around this weekend, just worth keeping an umbrella handy.

[c18_ens_prob]

GUS Overall, how confident am I in today's picture? I'd call it medium confidence today, clearly more sure than not, but well short of certain.

GUS The best agreement is on the quieter spots, we're virtually certain nothing much happens over most of the country tonight, it's the exact low pressure tracks two days out over South Australia where the models still disagree the most.

GUS If that changes, I'll update you in the next bulletin.

[c06_radar_now]

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

GUS My next bulletin is tomorrow morning, with an updated look at that inland storm risk and the Queensland flooding.

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

GUS Tonight's homework, if you're out after dark, look toward the west and see if you can spot a tall, anvil shaped cloud catching the last of the light, that's a storm spreading out at the top.

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

GUS Gus's Weather is a PandaVision production.