Gulf Country storms, Darwin heat warning | Australia weather Thu 5 Nov afternoon | Gus's Weather

Gulf Country storms, Darwin heat warning and WA fire danger: Thu 5 Nov

[c06_radar_now]

GUS G'day, I'm Gus, and this is your afternoon bulletin for Thursday the 5th of November.

GUS Right now there's heavy rain over Sydney, a severe heatwave warning is current for Darwin, and extreme fire danger is building over inland Western Australia.

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 this picture is only one minute old.

GUS The heaviest rain is very heavy and sitting near Townsville, again south-east of Townsville, near Mackay, and near Wagga Wagga in New South Wales, all on land and near people.

GUS On the capitals, Sydney has heavy rain right now, Canberra and Brisbane have rain, and Perth, Adelaide, Melbourne, Hobart and Darwin are clear on the radar.

GUS The model's own simulated radar for this hour also had rain building near Darwin and inland Queensland, but it missed the band now moving through Sydney, so trust the real radar there.

GUS I'll come back to the storm risk up north shortly, this is your overview.

[c06_radar_now]

GUS Every day I check each of the 6 weather models I use against what actually happened, and I re-tune how much I trust each one.

GUS I review them over a day, a week and a month, then three months and six months as the record grows.

GUS Over the last week, GFS has had the smallest error on daytime highs, about 2.3 degrees.

GUS On rain it's the American AI model that has been closest.

[c05_obs_now]

GUS Now the measured numbers from Bureau of Meteorology weather stations, since 9 am this morning.

GUS Lord Howe Island has picked up 9.8 millimetres of rain, the wettest spot in the country, with Victoria's East Gippsland not far behind: Combienbar 4.2 millimetres, Gelantipy 3.0 millimetres, Mallacoota 2.4 millimetres.

GUS It's actually raining right now at Mallacoota and at Tumut in southern New South Wales.

GUS The strongest gusts measured are way down south: Maatsuyker Island in Tasmania at 80 kilometres an hour, Gabo Island in Victoria at 72 kilometres an hour, Hartz Mountains at 67 kilometres an hour.

GUS That's a cool, blustery pocket in the south-east this afternoon while the north cooks.

[c07_lightning_now]

GUS Next, lightning strikes picked up by the Blitzortung lightning network, a volunteer network of ground sensors, over the last six hours.

GUS About 400 lightning strikes in the last six hours nationally, with the last hour's count growing to about 80 strikes, so activity is building again this afternoon.

GUS The busiest cluster is out at sea, well south-east of Sydney, but it's easing.

GUS The one to watch is about 74 kilometres east of Normanton, home to about 1,500 people.

GUS That matches exactly where our storm energy numbers are highest today, more on that shortly.

[c04_satellite]

GUS Here's the satellite, Himawari-9, which measures how cold the tops of clouds are in degrees,

GUS and cold means tall, and tall usually means a strong storm, so we can check what the radar can't show us.

GUS This is an observed picture, not a model, from one-thirty this afternoon, and it can see storm tops even where ground radar can't.

GUS Oh, I love this one: minus 80 degrees Celsius is about as cold as cloud tops get anywhere on Earth, that storm is punching into the very top of the atmosphere.

GUS There's also a storm about 150 kilometres south-west of Darwin with a top near minus 69 degrees.

GUS None of the eight capital cities have storm cloud overhead right now.

GUS The model's own storm map for this hour also missed that same storm, so today the model is running a touch behind what's actually happening.

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.

[c02_mslp_fronts]

GUS Zooming out to the pattern driving all this: a high sits over the Great Australian Bight at 1024 hectopascals,

GUS a unit of air pressure, and it's the lazy old high steering most of the country's weather.

GUS That same low in the Tasman Sea sits near 998 hectopascals, feeding the cool south-east change into Tasmania, Victoria and southern New South Wales.

GUS Up north weak, shallow low pressure areas near Broome and Mount Isa are helping draw moisture in off the warm seas.

GUS Out in the tropics, the European model's ensemble is watching two weak lows well out in the Pacific, each with around ten or eleven of its fifty-one members eventually reaching tropical storm strength.

GUS They're thousands of kilometres from Australia, there's no official warning, and it's far too early to say if either reaches our coast, so nothing to act on, just something forecasters watch.

[c07_cape]

GUS First stop on the storm ingredients: near Darwin, where storms build Friday afternoon.

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

GUS Near Darwin on Friday afternoon there's about 4500 joules per kilogram of it, a very full tank for early November.

GUS That energy comes from warm, humid air: the moisture in the air there, called the dew point, is about 25 degrees,

GUS and the air holds about 53 millimetres of moisture if you squeezed it all out, both very high numbers.

[c10_sim_radar]

GUS Next question: with all that fuel, what keeps a lid on it until the storm actually fires?

GUS Warm air sitting above the surface can act like a lid on a pot, stopping the bubbles of rising warm air underneath from breaking through.

GUS Near Darwin that lid is worth about minus 27 joules per kilogram, basically no lid at all.

GUS With barely any cap in place, the afternoon heating alone should be enough to pop storms up by mid-afternoon Friday.

[c12_index_map]

GUS Now the wind through the atmosphere, called shear, which is the difference in wind speed and direction from the ground up to about 6 kilometres.

GUS Near Darwin that shear is about 58 kilometres an hour, enough to tilt a storm's updraft and keep it organised.

GUS Picture a spinning top: on its own that's modest, but this shear can tilt a storm's spin upright and start it turning.

GUS Forecasters combine that into a supercell value, near Darwin it's high, meaning some of Friday's storms could rotate.

GUS A storm that starts to spin here isn't what Americans chase and call by that other name, here we'd call it a storm with destructive winds and large hail, and the Bureau watches those closely.

[c07_cape]

GUS Saturday night, similar storm fuel builds back up near Normanton in the Gulf Country, about 4500 joules per kilogram.

[c14_rain_wind]

GUS A wind change there should trigger storms overnight, with shear around 61 kilometres an hour and a risk of hail and damaging wind.

[c94_sounding_compare]

GUS Quick comparison between these two spots using a model's vertical slice of the atmosphere, think of it as a core sample through the air.

GUS The line on the right of this chart is the air temperature, the line on the left is how much moisture is in the air,

GUS and where they sit close together the air is nearly saturated.

GUS Near Normanton that moist layer reaches up to about 300 hectopascals, meaning the moist air goes very deep.

GUS Near Darwin the moist layer only reaches about 600 hectopascals, shallower than Normanton.

[c18_model_compare]

GUS I always check more than one model before I commit to a call, because they don't always agree.

GUS For Darwin over the next two days, GFS, the European model and the European AI model all land close together, around 8 to 9 millimetres of rain, so I trust that number.

GUS For the Gulf Country they spread more, from about 2 to 5 millimetres on average, so the amount is less certain.

GUS Storms can also join together overnight into one bigger cluster, called a mesoscale convective system, which is why one town can get a soaking while the next one misses out entirely.

GUS So the order for the next two days: Friday afternoon, strong storms near Darwin, then Saturday overnight, the same risk shifts to the Gulf Country near Normanton.

GUS Closer to the coast in both areas it's more a case of luck of the draw, some spots get a downpour, others stay dry, don't lock in any one town yet.

[c15_index_map]

GUS Fire danger is measured with an index that blends heat, dryness, wind and how dry the bush itself already is, called the drought factor.

GUS About 80 kilometres south of Port Hedland that index reaches 88 points, which the Bureau rates as extreme,

GUS with a drought factor measured from actual rainfall history at the top of that scale, as dry as it gets.

GUS A severe heatwave warning is also current for the Peninsula, Gulf Country, Northern Goldfields and Upper Flinders districts, where that same drought factor is at the top of the scale.

GUS An extreme heatwave warning from the Bureau is current for the Kimberley district in Western Australia, issued yesterday afternoon.

GUS Out here that means stock, stations and highway travellers, any fire that starts in country this dry and hot can run fast, so check bom.gov.au if you're in that area.

[c16_temp]

GUS The Bureau also has a severe heatwave warning current near Darwin, covering the Daly, Arnhem and Carpentaria districts, issued this afternoon.

GUS A severe heatwave warning is also current for the Pilbara and North Interior districts of Western Australia, where afternoon temperatures are reaching about 46.6 degrees.

GUS A further severe heatwave warning update for the Pilbara and North Interior districts keeps that danger in place, with the fire danger index there at 88 points.

GUS A heatwave warning means several hot days in a row, which is harder on the body than just one, especially for anyone older or working outdoors.

GUS If you're in any of these warned areas, check on elderly neighbours and keep up the fluids, the official detail is on bom.gov.au.

[c92_river_gauges]

GUS The Bureau also has a moderate flood warning current in Queensland for the Balonne River around Surat and Warkon, and for the Barcoo River downstream of Isisford and at Retreat and Blackall.

GUS There's also a moderate flood warning for the Balonne River to Surat, the Balonne River at Warkon, and the Balonne River at Mungindi, with levels tracked on the same gauge network.

GUS On the gauges, the Barcoo at Isisford Post Office is at 5.42 metres and rising, the height of the water on the gauge, not how deep it is at your feet.

GUS The Balonne at Warkon is at 7.87 metres and also rising, both tied to the Bureau's warnings, so check bom.gov.au for what that means for those towns.

GUS Elsewhere, rivers are rising after rain in several states: the Macintyre at Boggabilla in New South Wales,

GUS the Bunyip at Cora Lynn in Victoria, the Forth below Wilmot in Tasmania, and Cooper Creek at Walkers Crossing in South Australia.

GUS By contrast the Southern River near Perth and the Adelaide River near Darwin are both quiet, barely moving.

GUS Credit there to the Bureau of Meteorology's flood warning network for all those gauge readings.

GUS On the ground itself, SILO's rainfall data from the Queensland Government shows south-east Queensland and Victoria both running very wet,

GUS while the Top End is sitting dry, which is exactly the kind of country that bakes hard before a storm.

[c90_events]

GUS A quick look at the weekend's big outdoor events, because the weather matters for a few of them.

GUS At Rosehill Gardens in Sydney on Saturday for the Everest Carnival's Ladies Day, there's a real chance of thunder, so if lightning starts, the track will pause racing.

GUS At Flemington in Melbourne, both Champions Stakes Day Saturday and the Sandown 500 car racing this weekend carry a small chance of thunder, pack a jacket.

GUS Also over the Coral Sea about 40 kilometres north-east of Hervey Bay there's a pocket of storm energy today, mainly a concern for boats out that way rather than the coast itself.

GUS Punters at Flemington for Oaks Day this afternoon can leave the brolly at home, that one looks dry and calm.

GUS The Rugby League World Cup semi-final in Newcastle carries a smaller chance of thunder, worth a glance at the sky before kick-off.

[c20_town_table]

GUS Now the lap of the capitals, starting with the east coast.

GUS Brisbane's today high is around 35 degrees, a top of 26 degrees tomorrow with an overnight low of 19 degrees, and no rain forecast, nothing to worry about there.

GUS If you're mowing the lawn in Brisbane, best get it done before the warm change slides through.

GUS Sydney clears through this afternoon.

GUS Melbourne sits at 18 degrees today, dropping to a top of 22 degrees tomorrow with a low of 7 degrees, and no rain, dry but noticeably cooler.

GUS Why doesn't Melbourne ever get bored with its own weather? Because it never sticks to one forecast for long.

GUS That's one for the dads.

[c20_town_table]

GUS Perth's doing its usual thing, sunshine, and a bit of smugness about it.

GUS Adelaide's at 18 degrees today, a top of 21 degrees tomorrow with an overnight low of 11 degrees, dry both days, so good drying weather, get that washing out.

GUS Canberra sits around 19 degrees today, overnight low near 4 degrees tomorrow, and barely any rain, a cool one for spring so keep a jumper handy for the evening.

GUS Hobart's at 18 degrees today, cooling to a top of 16 degrees tomorrow with an overnight low of 12 degrees, and a touch of rain, about half a millimetre.

GUS Darwin stays in the mid thirties today and tomorrow, with an overnight low of 27, under that same heat warning.

[c01_verification]

GUS Quickly, how did I do calling yesterday's weather, checked against the Bureau's SILO observations.

GUS On whether it rained or not, I was right at 37 of 47 towns checked,

GUS and my daytime highs were off by about 2 degrees on average, generally a touch cool compared to what actually happened.

GUS Not a bad run, and it tells you roughly how much to trust today's numbers.

[c20_town_table]

GUS Now further out, using a European model's nine-day rain signal, this is rain only, it carries no thunderstorm information, so it can say wet, never storms.

GUS For the weekend itself, Brisbane, Canberra and Melbourne all look quiet, no organised storm signal flagged, though Melbourne gets a sharp cool change on Saturday, down near 13 degrees for the top.

GUS The signal to watch is mid next week: south-east Queensland turns wet Wednesday the 11th and Thursday the 12th, with the Gold Coast the wettest spot, up near 50 millimetres.

GUS Why did the Gold Coast cancel the beach day next Wednesday? Fifty millimetres of rain is a lot of sand to wash away.

GUS I'll see myself out.

GUS Central Queensland also turns wet around Sunday the 8th near Gladstone, and Victoria and Tasmania pick up showers this weekend then heavier falls again around Ballarat next Wednesday.

GUS Days two and three of this are fairly reliable, days four and five more a guide,

GUS and anything past that is only a signal that can shuffle completely by the next bulletin, so don't lock in plans around it yet.

GUS Where the ingredients line up with that rain, like south-east Queensland, the Top End and northern New South Wales around next Wednesday,

GUS there's plenty of that stored storm energy but nothing obvious yet to set it off, so it's worth watching rather than banking on.

[c02_mslp_fronts]

GUS My confidence in today's call is high, built mostly from strong agreement between the models on the rain near Darwin and on where the low pressure areas are sitting.

GUS What would change my mind: if that Pacific tropical low actually starts tracking toward Australia, or if Saturday's Gulf Country trigger arrives earlier or later than expected.

GUS I'll update all of that in the next bulletin.

[c06_radar_now]

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

GUS My next bulletin is tomorrow morning.

GUS If you'd like more of these, hit subscribe, and 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 Tell me in the comments what the sky's doing where you are right now, I do read them.

GUS Homework for today: if you're anywhere near Darwin tomorrow afternoon, watch for that first tower of cloud building early, it's usually the one that means business.

GUS Stay curious, and keep a brolly handy.

GUS Gus's Weather is a PandaVision production.