The reports here summarise weather events and climate news, including a round-up of their media coverage. They are archived in the relevant day's Daily Weather Summary to help make it a more complete record of the day's events. Timeliness of the reports is entirely at the mercy of my available time so, for the most up-to-date information, make good use of my media links here.
|Thursday 28 November 2019
Heat and dry to continue says BoM Climate Outlook
Thu 28 Nov 2019
The BoM issued its main monthly Climate Outlook today giving a high likelihood that warmer and drier than average conditions will continue through summer for almost all of the continent. The exception is that better than average rain is expected in NW WA from January, with this improvement slowly spreading east through to the end of the outlook period in March. However, apart from keeping daytime temperatures down in NW WA from January, the effect on both maximum and minimum temperatures is expected to be minimal, with over 80% probability of them being above average at least to the end of February.
The main driver of these conditions continues to be one of the strongest positive Indian Ocean Dipole events (IOD) since accurate records began in the early 1960s. It is caused by an anomaly in sea surface temperatures across the Indian Ocean: 1 to 2° below normal in the east near Australia and 1 to 2° above in the west near Africa. The cooler waters are producing our lack of rain while warmer waters have given large parts of eastern and central Africa disastrous flooding for months. Added to cooler SSTs in the Indian Ocean are cooler than normal SSTs to our east in the Coral and Tasman Seas and to our south in the Southern Ocean, so wherever the air comes from it will bring below average moisture.
The IOD normally begins to break down during December, but this year that breakdown is expected to be well into January. The strongly positive IOD will also influence the arrival of the Australian monsoon. The monsoon trough has been exceptionally late in leaving India this year; its normal arrival in Darwin is the last week of December, but this year it is not expected until well into January.
The second climatic factor that has been exacerbating fires and drought across southern Australia has been the continuing strongly negative Southern Annular Mode (SAM). Frontal systems have been pushing farther north than normal, but with a lack of moisture have only produced strong, drying NW to SW winds and duststorms, intensifying the danger of bushfires.
New regional climate guides designed for farmers
Thu 28 Nov 2019
The BoM and CSIRO have produced a set of 56 Regional Weather and Climate Guides produced specifically for farmers and mostly based on Australia's Natural Resource Management Districts. There is a strong focus on each region's climate risk, especially the changes that have occurred in recent years.
They have had considerable local input. The detailed FAQ says they have "been informed through interviews with local producers, agricultural advisers, local government, and other relevant stakeholders from the 56 NRM regions in Australia. Importantly this involved visiting the regions and gaining insights into what is relevant, and what's not, with regard to weather information used to inform agricultural decisions."
After a summary of significant changes in weather and climate in the last 30 years and a thumbnail sketch of the region's agriculture, there are sections that cover annual rainfall, rain reliability and timing, and temperature. Depending on region there may be sections on evaporation, frost, wet season timing, timing of autumn and spring breaks, evaporation and frequency of useful rain events. Each region covers the weather and climate issues that are specific to it so there is some variation, but all deal in detail with the impacts of climate change that have been occurring in the past 30 years.
If you haven't discovered these guides yet, visit the one for your area now.
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Widespread though patchy rain over central and SW QLD
Thu 31 Oct 2019
An average of 25mm has fallen over a large area of central and South West Queensland over the past 2½ days. Best falls were in an area bounded by Windorah to Blackall to Springsure to Clermont to Longreach to Windorah. The Bureau's flood raingauge maps show the location of rain for the 24 hours to 09:00 Wednesday 30th and today 31st, and the 12 hours to 21:00 today. As mentioned in my Tuesday post, the rain came courtesy of a slow-moving trough and upper low interacting with an infeed of moist air from the Coral Sea and northern QLD. It's been a while since we've seen such a happy coincidence.
Thunderstorms abounded in the unstable air, and those lucky enough to be under one or more had 50mm or better. Blackall scored best with 106mm at the Airport and 118mm at the Blackall Alert flood gauge, just east of town, between 09:00 Tuesday and 21:00 today. This was due to the town receiving five substantial dumps from thunderstorms. The mid-morning one on Wednesday produced 37.2mm in the hour to 11:10 of which 26.8 fell in the first 20 minutes. For Blackall, it is the first rain of any significance since 182mm fell on 27 and 28 March: only 26.4mm has fallen since then, and for the past 3½ months there has been zero rainfall.
Other significant totals in the 2½ days to 21:00 today were Echo Hills 88mm, Wharton Creek 78 and Mantuan Downs (West) 70 (all about 200km east of Blackall), Mount Harden 81 (70km SW of Blackall) and Glencoe 73 (just SE of Jericho).
This story from the ABC gives an idea of the joy the rain is bringing.
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QLD, NSW: Rain on the way
Tue 29 Oct 2019
The planets seem to be aligning for some widespread half-decent rain across drought-stricken central and southwestern areas of QLD in the next couple of days, then western, central and southern parts of NSW over the weekend.
The rare and welcome visitor is an infeed of moisture from the Coral Sea and waters north of QLD into the state. It has combined with a trough through central QLD and a very slow-moving upper low over the state's southwest to produce a mix of showers, areas of patchy rain and thunderstorms.
Rain began this afternoon in an area of central QLD bounded roughly by Blackall, Charleville, Injune, Alpha, Longreach and Blackall with light rain also extending into parts of the South West. Totals to 23.00 AEST this evening have been variable, as that's the nature of the system, but higher reports include Blackall AP 17mm, Chesterton (90km NE of Augathella) 26, Fairview Alert gauge (SE of Alpha) 30 and Jericho 21. Almost all of the BoM automatic raingauges in the area reported between a few and 10mm with over a dozen in the teens. The rainy spell is expected to last into Thursday 31st, with the southwestern quarter of the state likely to average 25 to 50mm, though some places will do better and others worse.
The area of moist air will be slowly drawn south into NSW by Friday in the northerly airstream ahead of the next southern frontal system which will also provide the lifting mechanism to turn the moisture into precipitation. Once again, a mix of showers, patchy rain areas and thunderstorms can be expected across the west, south and central parts of the state ahead of the front on Saturday and Sunday with an average of 15 to 25mm looking likely. The North West Slopes and Plains and Northern Tablelands should also see a little of that rain on Monday, possibly an average of 10 to 15mm.
Rainfall is the hardest weather element to forecast because of its variability over short distances, so it's best to take all forward estimates as best-guess averages for your broad area. As with the QLD situation, rain in NSW will be patchy, and the presence of thunderstorms can give you nothing or a lot depending on whether you bag one or not.
In addition, the models each paint different scenarios for what they calculate will happen - sometimes slightly different, sometimes significantly so. Right now, three main models (US, European and Australian) are predicting 53, 7 and 20mm for my home near Orange through to Tuesday 5th. The reason the European model amount is so low, for example, is that it expects the front at the weekend to take a more southern track, reducing its influence over northern and central NSW. The moisture would still be there, but the mechanism to make it fall as rain would be reduced. Successive model runs with updated information will continue to fine-tune the expected scenarios and show up as variations in each new issue of the OCF forecasts.
It won't be a drought-breaker in either state, but I hope it puts a smile on a lot of dusty faces.
NT, QLD: Record heat adds to dry season discomfort
Tue 22 Oct 2019.
A hot airmass brought bushfires† and storms to NE NSW and SE QLD around Thursday 17th before a cooler change pushing through southeastern Australia shifted the heat into the NT on Friday 18th.
In SE QLD, the heat ahead of the cooler change led to a record warm October night in places on the morning of Thursday 17th, with minimum temperatures of 22.3 at Injune and 22.4 at Texas their hottest for October in half a century of observations. At the same time, the hot airmass was driven into the NT Top End and far northeastern WA Kimberley and didn't budge until around Tuesday 22nd, setting new records every day.
In an area south of Darwin, the BoM rated the heatwave severe to extreme, the two highest levels. Tindal RAAF Base, just SE of Katherine, broke its previous all-time maximum temperature record twice recording 42.7 and 42.6 on the 17th and 18th (previous record 42.5 in a 32-year history). Douglas River Research Farm, 150km SSE of Darwin, exceeded their previous all-time record of 42.6 on three successive days with 43.2, 42.8 and 44.1 from the 18th to the 20th (34-year history). Darwin Airport, with a 78-year station history, got to within 0.7° of their all-time record of 38.9 on Monday 21st and may have gone higher except that a cooling seabreeze blew in at 12.30. See the records section in each day's Daily Weather Summary for details of all new records set.
The hot, dry and windy conditions across the Top End produced severe fire weather as this Bureau's satellite imagery shows. [SMH, ABC, Andrew Miskelly.]
Thu 17 Oct 2018. Outlook briefs
A throng of outlooks have been issued by the BoM in the past few days. Here we go:
- The mid-month Climate Outlook Update* (Archive summary here) was issued today. It firms up on earlier hints that more normal rainfall will spread unevenly across the country from early summer. An encouraging sign is that, even though the Indian Ocean Dipole (IOD) hit a record +2.15° last week, warmer than average sea surface temperatures are forecast to develop soon off the NW WA coast, bringing good chances of above normal rain in the northwest over the next few weeks and from December.
For most of the rest of the country, a weak negative phase of the Southern Annular Mode (SAM) together with a slow retreat from record positive levels of the IOD will keep things dry with likely heatwaves in the south and east from now into December. Also, as we're already beginning to see, positive IOD events are linked with more severe bushfire seasons in SE Australia. The Update video is worth a look, and the forward rainfall maps* help narrow down expectations for your neck of the woods in what is a fairly complex shift from dry to normal.
- As an aside, if you can't tell your SAMs from your IODs, ENSOs and SOIs - and they're critical in driving our climate over periods of months rather than days - here are some good videos, best viewed on something larger than a mobile. Starting with SAM, there's an enjoyable quick introduction from the VIC DPI. It was made in 2010 and is slanted, naturally enough, to Victorian farmers. The much more recent BoM explainer brings the science up to date, but lacks a cute cattle dog.
Same with IOD. Here's the Victorian one and here's one from BoM.
And the El Niño-Southern Oscillation (ENSO) - the VIC DPI with dog and BoM. Go here for more detail on the Southern Oscillation Index (SOI), how it's calculated and what it means.
(If you're hooked on the cattle dogs, here's a complete list of the Climatedogs videos.)
- The ENSO Wrap-Up and Climate Model Summary were issued on Tuesday. Most ENSO indicators remain neutral and are expected to remain so into 2020. Unusually, the Southern Oscillation Index, which is based on the difference in atmospheric pressure between Darwin and Tahiti, is El Niño-like due to very high pressure at Darwin. However, this is an anomaly caused by the very high IOD which has encouraged strong easterly trade winds across the northern Indian Ocean, causing upwelling of cooler water near Australia. The Overview tab of the ENSO Wrap-Up is a succinct explanation of how it fits together and what it means for the next few months.
- The annual Tropical Cyclone Outlook was released last Friday. It expects fewer cyclones than average in the Australian region during the cyclone season, which runs from 1 November to 30 April. Between 9 and 13 tropical cyclones occur each season in our region, of which four typically cross the coast. The probability of fewer cyclones is based on the Southern Oscillation Index (SOI) and the sea surface temperature anomaly in the Niño3.4 area of the Pacific Ocean. Overall, the BoM expects a 35% chance of more tropical cyclones than usual for the Australian region as a whole, which means a 65% chance of fewer. Outlook accuracy has been high in the past for the overall Australian region, though less so for subregions. Full details are in the Outlook, and the Further Information tab is worth reading to understand what you're looking at.
- Finally, spring and summer are the times of Australia's most severe weather, and BoM issued this video on Sunday summarising what to expect across the gamut of bushfires, heatwaves, flooding, tropical cyclones and severe thunderstorms in the coming months.
Drought continues or worsens after dry September
Tue 8 Oct 2019
Last month was the tenth driest September in the past 120 years of reliable rainfall records across Australia. The 2¾ years from January 2017 to September 2019 are the driest in the record book in the last 120 years in the Murray-Darling Basin as well as for NSW overall.
| September saw less than 20% of average rain across most of the country. BoM.
September again saw widespread failure of rain thanks to the most strongly positive Indian Ocean Dipole (IOD) in almost 20 years. In late September, the IOD weekly value hit an average of +1.76°, the highest since at least 2001. The IOD measures the difference in ocean temperature between the west and east tropical Indian Ocean. A strongly positive IOD shows waters to Australia's northwest are cool and produce less moisture to be carried across the continent as northwest rainbands.
September saw less than 20% of average rain across most of the country, the small exceptions being pockets of coastal SA, VIC and NSW. The TAS East Coast received a much-needed dowsing on 6-7 September. What appears to be a phenomenal rainfall streak from the Kimberley to around Alice Springs is something of an illusion - average rain there in September is minimal, so the 5 to 25mm received provided some stupendous if rather meaningless percentages. WA fared worst with the 5th driest September on record while rain in the Murray-Darling Basin was the 9th lowest. TAS did best, but was still 27% below average while VIC came second-best on 36% below.
The dry September made the nine months from January to September the 4th lowest January to September average for all Australia in the 120-year record. Added to this were above average temperatures in September which made January to September the second warmest in the 110-year record. The resulting higher than normal evaporation means that root-zone continued below average into August, the last figures available, for most of Australia.
|Rainfall deciles for the three years from 1 October 2016 to 30 September 2019. Almost all the Murray-Darling Basin lies in the bottom 10% of 3-yearly totals in the past 120 years while large areas of the basin in northern NSW and southern QLD are at record low levels. BoM.
The Monthly Drought Statement issued on Tuesday 8th shows the Murray-Darling Basin as a whole has had record low rainfall in the 2¾ years from January 2017 to September 2019 with the worst impacts being in the northern MDB. Compared to the Bureau's standard 1961 to 1990 period, MDB overall has been 37% below average, the northern MDB 40% below average and the whole state of NSW not much better at 34% below average.
The Statement says "The deficiencies have been most extreme in the northern Murray–Darling Basin, especially in the northern half of New South Wales and adjacent southern Queensland, where areas of lowest on record rainfall extend from the Great Dividing Range west as far as Dubbo and Walgett. Some of the largest rainfall deficiencies have occurred in the upper catchments of some of the major tributaries of the Darling, including the Macquarie, the Namoi–Peel, the Gwydir, and the Border Rivers."
Because of the length of the drought, most dams on the tributaries that feed the Darling River are between 1 and 8% full, and flow in the rivers at most gauges, including the Darling, is down to a trickle or has ceased. The current percentages of full capacity in the largest dams are:
- Burrendong, Macquarie River (NSW): 4.4%
- Split Rock, Manilla > Namoi Rivers (NSW): 1.6%
- Keepit, Namoi River (NSW): 0.9%
- Copeton, Gwydir River (NSW): 8.5%
- Pindari, Severn River (NSW): 4.9%
- Beardmore, Balonne River (QLD): 4.7%
- Glenlyon, Pyke Creek > Dumaresq River (QLD): 3.6%
The Menindee Lakes are effectively empty with 0% in Lakes Menindee, Pamamaroo and Cawndilla and 5% in Lake Wetherell.
This is what most of the Darling River looks like now. The sentiments are food for thought and action. And in case you're wondering, Useless Loop on Heiresson Prong does exist.
- * Asterisked links are to real-time material that was correct at time of posting, but may expire or be replaced by newer material.
- † Requires translation to English
- ‡ Linked site has partial paywall
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