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For frequently asked questions, please check our Knowledge Base. LegendGlossaryKnowledge BaseAbout Us CONTACT US -------------------------------------------------------------------------------- For general feedback and enquiries, please contact us through our Help Desk. Make an enquiry AUSTRALIAN WEATHER Search Icon Radar Satellite Synoptic Chart Sydney 8.2°C Melbourne 4.9°C Brisbane 10.6°C Perth 5.5°C Adelaide 11.5°C Canberra -3.9°C Hobart 8.6°C Darwin 21.5°C Sunday, 4 August 4:35AM AEST Icon Step ArrowIcon PlayIcon Step Arrow LegendLayer Gradient Legend: Rain Radar Icon Arrow Selector Light Heavy Daily Forecast Live Extremes Warnings Map Layers Layer Gradient DAILY FORECAST * Today * Tomorrow Rain over WA's Pilbara & interior, spreading over SA & the NT, with a moist airstream. A cold front brings showers & gusty winds to Tas & southern Vic. Humid onshore flow is causing showers over north QLD. Dry elsewhere with high pressure. Now Min Max Mostly CloudySydneyNSW 8.2°C 7°C 18°C Mostly CloudyMelbourneVIC 4.9°C 3°C 15°C Mostly SunnyBrisbaneQLD 10.6°C 9°C 23°C SunnyPerthWA 5.5°C 5°C 20°C RainAdelaideSA 11.5°C 8°C 15°C Mostly CloudyCanberraACT -3.9°C -4°C 14°C Mostly SunnyHobartTAS 8.6°C 6°C 14°C Clearing ShowerDarwinNT 21.5°C 21°C 32°C WEATHER MAPS Radar Satellite Synoptic Chart DAILY FORECAST * Today * Tomorrow Rain over WA's Pilbara & interior, spreading over SA & the NT, with a moist airstream. A cold front brings showers & gusty winds to Tas & southern Vic. Humid onshore flow is causing showers over north QLD. Dry elsewhere with high pressure. Now Min Max Mostly CloudySydneyNSW 8.2°C 7°C 18°C Mostly CloudyMelbourneVIC 4.9°C 3°C 15°C Mostly SunnyBrisbaneQLD 10.6°C 9°C 23°C SunnyPerthWA 5.5°C 5°C 20°C RainAdelaideSA 11.5°C 8°C 15°C Mostly CloudyCanberraACT -3.9°C -4°C 14°C Mostly SunnyHobartTAS 8.6°C 6°C 14°C Clearing ShowerDarwinNT 21.5°C 21°C 32°C LATEST WARNINGS AUS Icon/Expand-Collapse/Solid/Expand (white) * Miscellaneous warning NSW/ACT3:52AM AEST Gale Warning For Western Area * Miscellaneous warning NSW/ACT3:52AM AEST Gale Warning For Western Area * Miscellaneous warning NSW/ACT3:51AM AEST Gale Warning For Southern And Southeastern Areas * Coastal wind warning QLD10:00PM AEST Strong Wind Warning for Torres Strait & Peninsula and Cooktown coasts * Coastal wind warning TAS10:00PM AEST Strong Wind Warning for South East, South West and Central West coasts All Warnings EXTREMES AusNSW/ACTVICQLDWASATASNT LIVE EXTREMES High Temperature Highest Temp Cocos Island Ap, WA 26.2°C (1:00AM GMT+6:30) Aug Long Term Average: 28.1°C Aug Record: 30.6°C (2022) Low Temperature Lowest Temp Cooma Ap, NSW -6.4°C (4:30AM AEST) Aug Long Term Average: -1.5°C Aug Record: -13.9°C (1994) Rain Wettest Low Rocky Point, TAS 19.2mm (Since 9am) Aug Long Term Average: 149.0mm Aug Record: 43.6mm (2013) TODAY’S EXTREMES High Temperature Highest Temp Fitzroy Crossing, WA 34.5°C (2:58PM AWST) AUG Long Term Average: 33.4°C AUG Record: 39.5°C (2020) Low Temperature Lowest Temp Cooma Ap, NSW -6.6°C (4:29AM AEST) AUG Long Term Average: -1.5°C AUG Record: -13.9°C (1994) Rain Wettest - - (24h to 9am) Long Term Average: - Record: - THIS MONTH’S EXTREMES High Temperature Highest Temp Yampi Sound (Defence), WA 35.2°C (2 August) Aug Long Term Average: - Aug Record: - Low Temperature Lowest Temp Cooma Ap, NSW -9.0°C (2 August) Aug Long Term Average: -1.5°C Aug Record: -13.9°C (1994) Rain Wettest South Johnstone, QLD 64.8mm (MTD) Aug Long Term Average: 91.7mm Aug Record: 414.3mm (1959) THIS YEAR’S EXTREMES High Temperature Highest Temp Carnarvon Ap, WA 49.9°C (18 February) JAN Long Term Average: 31.4°C JAN Record: 47.8°C (2015) Low Temperature Lowest Temp Liawenee, TAS -13.5°C (4 July) JUN Long Term Average: -1.0°C JUN Record: -11.2°C (2013) Rain Wettest Tully, QLD 4236.0mm (YTD) Annual Average: 4070.4mm Annual Record: 7898.0mm (1950) Records data is supplied by the Bureau of Meteorology and has not been independently quality controlled. LATEST NEWS Previous 03 Aug, 3:06PM AWST Perth's second warmest July on record 03 Aug, 10:59AM AWST Midwinter soaking for the Pilbara and the interior 02 Aug, 2:36PM AWST Snow season cracks the magic metre 02 Aug, 7:53AM AWST Sydney recovering from coldest, windiest spell in 13 years 01 Aug, 12:17PM AWST July 2024, the windiest month in a year 01 Aug, 9:38AM AWST Darwin's 'wettest' July in 23 years 01 Aug, 8:22AM AWST Drenching and wild light show for WA PlayIcon 07 Mar, 9:09AM AWST Climate Update - Summer 2022-23 Next * 1 * 2 * 3 * 4 CLIMATE UPDATES Previous 31 Jul, 11:13AM AWST Negative Southern Annular Mode strengthening in Southern Hemisphere 24 Jul, 11:39AM AWST Could Australia see a negative IOD in 2024? 12 Jul, 10:41AM AWST Sudden stratospheric warming event underway – here's what it means for Australian weather 20 Jun, 1:43PM AWST Neutral Indian Ocean Dipole more likely this year 07 Jun, 11:45AM AWST Winter 2024 outlook for Australia 22 May, 11:46AM AWST May to become Earth's 14th consecutive month of record ocean warmth 21 May, 10:48AM AWST Increasing signs a positive IOD could develop this winter 16 May, 1:18PM AWST Australia's coldest April since 2015 during Earth's warmest April on record Next * 1 * 2 * 3 * 4 WEATHER IN BUSINESS Previous 01 Aug, 12:17PM AWST July 2024, the windiest month in a year 22 Jul, 11:17AM AWST Another windy week 05 Jul, 10:14AM AWST Unusual wind direction to elevate wind power 01 Jul, 10:25AM AWST Low wind power week coinciding with high demand 24 Jun, 12:15PM AWST Finally, a great wind power week 14 May, 11:01AM AWST Can auroras affect aeroplanes? 08 May, 7:23AM AWST How severe thunderstorms impact energy infrastructure 23 Apr, 8:07AM AWST Wind returning to southeastern Australia Next * 1 * 2 * 3 * 4 LATEST NEWS -------------------------------------------------------------------------------- 03 Aug 2024, 3:06PM AWST PERTH'S SECOND WARMEST JULY ON RECORD After parts of southwest Australia endured severe storms and ferocious winds last week, Perth has completed a hat-trick after experiencing its second-warmest July in records going back to 1944. The Perth airport site had an average overall temperature of 14.5ºC during July, a whopping 1.4ºC higher than the 80-year average. Maximum temperature themselves were the fifth highest on record (19.4ºC) and were the warmest on average since 2020 (19.5ºC). Other locations in the region told a similar story: Bunbury had its third-warmest July since records began in 1996 (13.5ºC average temperature) and second-warmest average maximum temperature (18.1ºC). Albany had its warmest July since records began in 2012 (13.0ºC average temperature). Merredin, between Perth and Kalgoorlie, had its third-warmest July since records began in 1966 (12.5ºC average temperature). Figure: Mean temperature anomaly of July 2024 compared to the 1961-1990 baseline temperatures (Bureau of Meteorology). As seen from the mean temperature anomaly map, the majority of Western Australia was 2-3ºC above the 1961-1990 average. With winter being the wettest season across much of southwest Western Australia, it makes sense that moisture levels were elevated across the region. The figure below shows that the specific humidity anomalies were especially high for WA's Central Wheatbelt and surrounds. High humidity means dewpoints were elevated, hence the much warmer temperatures throughout July. Figure: Near-surface specific humidity anomalies of July 2024 compared to the 1961-1990 baseline (NOAA Physical Sciences Laboratory). This moisture came with the consequence of rainfall over the southwest, which we saw most recently in the final hours of July. Geraldton had its highest July rainfall in 12 years of records (157mm, average of 66.3mm) Bunbury had its wettest July since 2000 (232.0mm, average of 146.3mm) Whilst August has started off close to average so far across the southwest in terms of temperatures, there are indications of increased warmth next weekend ahead of a potentially significant cold front. Be sure to keep an eye on the latest forecasts and warnings on our website. 03 Aug 2024, 10:59AM AWST MIDWINTER SOAKING FOR THE PILBARA AND THE INTERIOR Parts of the Pilbara have experienced an unseasonably soggy few days, as a low pressure trough gathered moisture over the Indian Ocean and is now dragging it across the region and into the interior. The mass of cloud associated with the trough, which we talked about earlier in the week, now dominates the current satellite images of Australia. Image: Himawari enhanced visible true colour satellite image of Australia Carnegie station, almost smack bang in the centre of WA, picked up 35.0mm of rain in the 24 hours to 9am this morning, representing its highest August total in records dating back to 1943. Some other significant statistics from the last few days include: Karratha (26.8mm in 24 hours to 9am Friday) had their highest August total since 1974 Warambie (11.5mm in 24 hours to 9am Friday) had their highest August total since 1965 Port Hedland (28.2mm in 24 hours to 9am Saturday) had their highest August total since 1983 and highest overall since January 2023 Paraburdoo (11.8mm in 24 hours to 9am Saturday) had their highest August total since 1988 Other significant totals in the last 24 hours include 25.6mm at Ironbridge Ap, 20.8mm at Varanus Island and 15.6mm at Roebourne Ap. Most of these locations typically average less than 10mm of rainfall in August. The trough will continue to drive rain over the Pilbara, as well as spreading into western parts of the Kimberley as the day wears on. Overall, another 20-30mm of rain is possible in some of these areas by the end of the day. Rain is also falling over the interior of WA, and spreading into neighboring NT and SA, with eastern WA towns such as Warburton and Giles registering a few drops in the rain gauges this morning. Indeed, Warburton’s 24 hour total of 4.4mm is more than half of its August average (8.3mm). Image: ECMWF forecast accumulated rainfall to 10pm EST Mon 5th of August Showers will begin to clear from most of WA tomorrow while spreading further into SA and the southern NT, as an upper-level trough sweeps across the country steering the rain east. While the trough will spread showers across large portions of the country in the coming days, most of the rain from this system will fall over the western half of the country. 02 Aug 2024, 2:36PM AWST SNOW SEASON CRACKS THE MAGIC METRE Approximately halfway through the Australian snow season, the good news is that we've got a decent season on our hands after heavy snowfalls on each of the last two weekends. In raw statistical terms, season 2024 is still short of the historical average in terms of peak depth. But with decent a base, and with six weeks ahead that historically have been productive for snowfalls, there's every chance this will become a good or even excellent season. This week, Snowy Hydro measured a depth of 124.6 cm at Spencers Creek, at an elevation of 1830m roughly halfway between the NSW ski resorts of Perisher and Thredbo. Snowy Hydro has been measuring snow there since 1954, and the long-term average peak season depth for the site is just under two metres, so as mentioned, season 2024 has a way to go. But any time you crack the magic metre mark, it means there is usually pretty good snow coverage for snow sports across the mountains. A few points worth making regarding the above graphs: The first is that season 2023 (the light blue line) peaked early at Spencers Creek on July 13. Indeed, that the was the earliest peak season depth on record. That’s because August and September were warm and mostly dry in 2023. This year, there are still indications that August and early September could be a productive period for snowfalls. One such indicator is the negative Southern Annular Mode (SAM). So even though the running 2024 peak depth is still a few centimetres below last year's, it seems likely that 2024 will overtake last year. A final point worth mentioning relates to the second graph, which shows snow depth at Three Mile Dam. As the lowest of Snowy Hydro's three snow depth measuring sites, Three Mile Dam has struggled to amass any significant depth in recent seasons. And while snow was hardly deep at the site at the most recent reading (25 cm on July 24), that was still a greater depth than at any time in 2023. And as you can see on the video above which was taken recently, cross-country ski conditions at Three Mile Dam haven't been too bad lately. So all in all, the Aussie snow season is in reasonable shape. Check the snow reports for Thredbo, Perisher, Charlotte Pass, Selwyn Snow Resort, Mt Buller, Falls Creek, Mt Hotham, Mt Baw Baw and Ben Lomond in Tasmania for more. The only downside at present is that we've seen a snow-free week since last Saturday, and another dry week looms on the horizon next week. Temperatures have been cold so not much melting has occurred, but unfortunately, there's no major snow-bearing system on the current charts either – although early indications suggest the pattern is likely to change by mid-August. As ever, check our snow page for the latest forecasts, cams and more. CLIMATE UPDATES 31 Jul 2024, 11:13AM AWST NEGATIVE SOUTHERN ANNULAR MODE STRENGTHENING IN SOUTHERN HEMISPHERE Ongoing stratospheric warming above Antarctica looks set to influence weather patterns across the Southern Hemisphere into August as a strong negative Southern Annular Mode (SAM) takes shape. The atmosphere above East Antarctica started to warm abruptly during the middle of July. This warming initially started in the polar stratosphere, around 30-40km above East Antarctica, but its influence has since filtered down towards the surface in the past fortnight. Image: Modelled surface air temperature anomaly over Antarctica on July 31, 2024. Source: ClimateReanalyzer.org When the air above Antarctica gets warmer than usual during winter, it can weaken and destabilise the Southern Hemisphere’s polar vortex. This weakening of the polar vortex causes the westerly winds that flow around Antarctica to expand towards the equator, allowing polar air masses to spread further into the mid-latitudes. The expansion of the circumpolar westerlies and the associated cold air is defined as a negative phase of the SAM. The Southern Annular Mode (SAM) is an index used to monitor the position of the westerly winds that flow from west to east around Antarctica. When the SAM is in a negative phase, these westerly winds, and the cold fronts and low pressure systems they carry, are located further north than usual for that time of year. When the SAM is positive, the westerly winds, cold fronts and low pressure systems are located further south than usual for that time of year. The SAM has recently dipped into a negative phase in response to stratospheric warming above Antarctica. Forecast models suggest that further stratospheric warming will take place in the opening fortnight of August, causing the current negative SAM to get even stronger. The graph below shows the SAM forecast from the NOAA Climate Prediction Center, based on the GFS model. This model suggests that the SAM index is currently sitting around -3 and could dip below -4 into the opening week of August. Other forecast models also show the current negative SAM phase lingering into August. Image: SAM (also called the Antarctic Oscillation or AAO) index observations and forecast, showing a strong negative SAM phase underway that is expected to persist into August. What does this mean for Australia? As mentioned earlier, a negative SAM causes the westerly winds, cold fronts and low pressure systems that circulate Antarctica to move further north than usual. In winter, a negative SAM typically causes the following impacts in Australia: More frequent cold fronts and low pressure systems over southern Australia Increased rainfall and snow potential in southwest and southeast Australia Reduced rainfall in parts of eastern Australia Stronger winds in the southern half of Australia However, no two negative SAM events are the same and there are other factors that will determine how this negative SAM impacts Australia’s weather in the coming weeks. One key factor will be the shape of the circumpolar westerly wind belt as it expands away from Antarctica. Forecast models suggest that the westerlies will meander as they flow through the Southern Hemisphere’s mid-latitudes, which is called a meridional pattern. This meandering flow will cause a long-wave pattern with large nodes of cold air and low pressure next to regions of warmer air and higher pressure in the mid-latitudes. This alternating pattern of low and high pressure should cause countries in the Southern Hemisphere’s mid-latitudes to fluctuate between periods of relatively warm and stable weather and periods of colder and more unsettled weather during the coming weeks. Image: Modelled temperature and geopotential height at 500 hPa (about 5km above sea level) on August 6, 2024, showing nodes of cold air and low pressure surrounding Antarctica. Source: ECMWF Image: Modelled temperature and geopotential height at 10 hPa (about 30km above sea level) on August 6, 2024, showing an elongated polar vortex in the stratosphere above Antarctica. Source: ECMWF The current strong negative SAM phase will make rain, wind and cold weather more likely in southern Australia during late winter and early spring. However, this wintry weather will likely be interspersed with periods of drier and more stable weather. If we do continue to see this alternating pattern of amplified high and low pressure beyond August, it will increase the likelihood of large thunderstorm outbreaks in Australia during spring. It’s too early to know if, and how, this stratospheric warming event will continue to influence weather patterns in the Southern Hemisphere into late spring and summer. However, past stratospheric warming events have had a strong influence on late spring and summer weather in Australia, so this will be something to keep a close eye on in the coming months. 24 Jul 2024, 11:39AM AWST COULD AUSTRALIA SEE A NEGATIVE IOD IN 2024? A wet spring could be on the cards for large parts of Australia, with several models suggesting a negative Indian Ocean Dipole could develop in the Indian Ocean. A negative Indian Ocean Dipole (IOD) refers to a pattern of sea surface temperatures in the tropical Indian Ocean that causes more moisture-laden air to flow towards Australia. These negative IOD events, which occur on average once every five years, typically enhance northwest cloudbands over Australia and produce above-average rain over large areas of the country's south and southeast during winter and spring. The Bureau of Meteorology declared yesterday that there is an increased chance of a negative IOD in spring. This declaration comes after four out of five climate models are now predicting a negative IOD event to emerge in spring, before returning to neutral during the beginning of summer. Interestingly, the Bureaus’ model is erring on the positive side during spring. Images: Global climate model IOD forecasts (top to bottom) for September, October and December. Phases of the IOD have impacted Australia’s weather during the last three years, with negative events occurring during 2021 and 2022, while in 2023 we saw a strong positive IOD. As such, 2021-2023 is tied with 1996-1998 as the longest stretch in which the IOD was observed to be in a non-neutral state. If we were to see a negative IOD develop in 2024, this would become the longest stretch we have seen the IOD in a non-neutral state since reliable records of the IOD began in 1960. As you can see in the graph below the IOD is currently in a neutral state, which means it’s not impacting Australia’s weather this winter. For a negative IOD to be declared, the Bureau requires sea surface temperatures in the Indian Ocean to have remained near or exceeded the negative IOD threshold of -0.4°C (blue in image above) for the last eight weeks. For a negative IOD to develop, the ocean and atmosphere need to be ‘coupled’, which means that the difference in sea surface temperatures in the western (cooler) and eastern (warmer) Indian Ocean is sustained by an atmospheric circulation. This requires winds to be more westerly and northerly than usual over northern Australia, allowing warmer than normal water to be dragged towards Australia’s northwest coast. There are signs that the atmosphere is mirroring the oceans, like the winds being more northerly than normal near Indonesia, but there is a long way to go yet. Impacts of a negative IOD A negative IOD can have a significant impact on Australia’s weather during winter and spring. The pattern of sea surface temperatures during negative IOD events typically cause more atmospheric moisture to flow over Australia from the northwest. This moisture can fuel vast northwest cloudbands, which can cause: Widespread rain Increased thunderstorm activity Flooding An increase in snow, particularly in winter and early spring Reduced solar output The map below shows how negative IOD events typically affect Australia’s winter-spring rainfall. Image: This map shows the impact a negative IOD would typically have on Australia's rainfall during winter and spring. Source: Bureau of Meteorology The increased cloud cover and associated rain caused by negative IOD episodes can cause: Below average daytime temperatures across large areas of the country. A reduced risk of early season extreme heat Warmer than average nights, with cloud trapping the heat in overnight. Increased humidity across large parts of the country. Images: These maps show the impact a negative IOD would typically have on Australia's maximum (top) and minimum (bottom) temperatures during winter and spring. Source: Bureau of Meteorology We will continue to watch the Indian Ocean closely in the coming months and update you. 12 Jul 2024, 10:41AM AWST SUDDEN STRATOSPHERIC WARMING EVENT UNDERWAY – HERE'S WHAT IT MEANS FOR AUSTRALIAN WEATHER A rare sudden stratospheric warming event is beginning to occur above Antarctica, and it may influence Australia’s weather in the coming weeks. The term sudden stratospheric warming (SSW) refers to an abrupt increase in air temperature high above either of Earth’s polar regions, typically on the magnitude of tens of degrees Celsius in a few days. This warming occurs in a layer of the atmosphere called the stratosphere, roughly 30 to 40km above the surface. While warming in the stratosphere does not immediately (or always) affect weather patterns near the ground, SSW events can filter down through the atmosphere and influence tropospheric weather in the weeks following the initial SSW. If an SSW event does make its way down to the troposphere, it can cause the tropospheric polar vortex to weaken, which allows cold polar air to drift further away from Antarctica (or the Arctic if in the Northern Hemisphere) and spread towards the mid-latitudes. Through this domino effect, SSW events can cause the Southern Annular Mode (SAM) to shift into a negative phase, which can have the following impacts in Australia during winter: More cold fronts and low pressure systems over southern Australia Increased rainfall and snow potential in southwest and southeast Australia Reduced rainfall in parts of eastern Australia Stronger winds in the southern half of Australia The Southern Annular Mode (SAM) is an index used to monitor the position of the westerly winds that flow from west to east between Australia and Antarctica. When the SAM is in a negative phase, these westerly winds, and the cold fronts and low pressure systems they carry, are located further north than usual for that time of year. When the SAM is positive, the westerly winds, cold fronts and low pressure systems are located further south than usual. Sudden Stratospheric Warming underway Warming has been detected in the stratosphere above the Antarctic region over the past week, revealing that an SSW event is starting to occur in the Southern Hemisphere. Some forecast models predict that this stratospheric warming will continue over the next week and start to filter down through the atmosphere later this month. The graph below shows observed stratospheric temperatures in red and the forecast from one model in green. From these lines you can see a sudden increase in the temperature beyond the normal range, potentially getting even warmer than any other observed event at this time of year. Image: Observed and forecast 10hPa temperature over the Southern Hemisphere’s polar region (90°S to 60°S) according to the GFS model. It is currently unclear whether the stratospheric warming will influence weather closer to the ground in the coming weeks. However, some models are already showing signs that the SSW signal will descend to lower altitudes during the second half of July. If this trend continues, it will increase the likelihood of a shift towards a negative SAM in late July or August. Videos: Forecast temperatures at the 10hPa (top) and 100hPa (bottom) levels in the atmosphere, according to the GFS model. The first animation shows warming over East Antarctica during the middle of July, which displaces the cold air within the stratospheric polar vortex. The second animation shows warming predicted to the south of Australia later in the month, indicating the downward progression of the SSW signal. Since April, Australia has been affected by a stagnant long-wave ridge pattern, leading to persistent high pressure in the Bight. As a result, there has been drought in WA and SA, abnormally wet conditions along the east coast, and very low wind over western Vic. This SSW event may disrupt this pattern for the Australian region. The images below show one forecast model predicting a shift towards lower sea level pressure near Australia in August, and an associated increase in precipitation for southern Australia, which are both consistent with a shift towards negative SAM. Image: Forecast mean sea level pressure anomaly in August 2024 according to the ECMWF SEAS5 model. Image: Forecast precipitation anomaly in August 2024 according to the ECMWF SEAS5 model. What causes Sudden Stratospheric Warming? SSW can be caused by large atmospheric ‘waves’ propagating upwards through the atmosphere and crashing into the stratospheric polar vortex. These waves can warm the polar stratosphere and weaken, or even reverse, the westerly winds that typically circulate above the poles in winter. An SSW event can be classified as minor or major based on the magnitude of warming and changes to the wind speed and direction in the stratosphere: A minor SSW occurs when the polar temperature increases by 25°C or more within one week at any stratospheric level A major SSW requires an increase in temperature AND a reversal of the westerly winds at the 10hPa level in the polar regions. Only a few SSW events have been observed in the Southern Hemisphere, with the most recent one occurring in 2019. Weatherzone’s meteorologists will be keeping a close eye on the current SSW signal and updating the Weatherzone News feed in coming weeks. 20 Jun 2024, 1:43PM AWST NEUTRAL INDIAN OCEAN DIPOLE MORE LIKELY THIS YEAR Early last month, we said that May would be a make-or-break month for the positive Indian Ocean Dipole (IOD) that could be forming this year. Turns out, it has most likely broken. A positive IOD occurs when the trade winds along the equator blow to the west instead of the east, causing an upwelling of cold water near Indonesia, and warm waters to congregate near Africa. When the pattern is established, Australia tends to see far less rainfall move from the northwest of the country to the southeast in the form of cloudbands. Back in early May, there were strong signs that a second consecutive positive IOD could develop. The main pieces that were starting to fit together were: Strong southeasterly winds across the southern Indian Ocean Upwelling occurring off the Indonesian island of Java Near record warm oceans near the Horn of Africa Warm waters in the Bay of Bengal Image: Sea Surface Temperature anomalies on May 19, 2024. Cool waters in the IOD East and warm waters in IOD West indicate a positive IOD pattern developing. However, there was a big caveat to that May forecast: tropical activity during the month had the potential to help or hinder the formation of the positive IOD this year. It can do this by changing atmospheric patterns, and causing cold water to upwell beneath stronger systems, like tropical cyclones. During May, there were three significant tropical cyclones in the Indian Ocean, each upwelling cool waters in locations that set back the formation of a positive IOD. Two out-of-season tropical cyclones formed quite close to the equator near Africa, being named Tropical Cyclone Hidaya and Tropical Cyclone Ialy. Both of these systems were Category 2 strength on the Australian scale, with winds peaking at 140km/h and 120km/h respectively, and brought heavy rainfall to Tanzania and Kenya. Together, these tropical cyclones cooled waters in and near the 'IOD West' region by up to 4 degrees. Furthermore, they altered the overall pattern of winds, allowing coastal upwelling of cold water to start near the Horn of Africa. Since winds generally move from cooler locations to warmer ones (like with a sea breeze), westerly winds have started to increase in the western Indian Ocean. Over in the Bay of Bengal, Severe Cyclonic Storm Remal also reached the equivalent of a Category 2 system on the Australian scale, with winds up to 140km/h before making landfall over northeastern India and Bangladesh. Upwelling of water in the Bay of Bengal reduced ocean temperatures by 3-4 degrees but did so over a very large area. While tropical cyclones in the Bay of Bengal during April and May have been known to kick off a positive IOD, this cyclone essentially hit the ‘reset’ switch, in that the conditions to create a positive IOD now have to start from scratch. Finally, the strong pulse of tropical activity changed the wind patterns in the Indian Ocean. Westerly winds were much stronger than normal in the centre of the Basin, and southeasterly winds eased off near Indonesia. Since coastal upwelling there relies on constant southeasterly winds, the disturbance in May was enough to stop the upwelling and warm up the surrounding waters. Image: Sea Surface Temperature anomalies on June 17, 2024. Areas of cooling are circled in blue, and areas of warming are circled in red. Now that most of the conditions that were building the positive IOD have been disrupted, the IOD index has returned to near-zero. This means that is it now much less likely that a positive IOD will develop this year, and the IOD will most likely remain neutral. With a neutral IOD, northwest cloudbands can bring rainfall to the southeast of Australia, much to the relief of South Australia in particular which had its 2nd driest autumn on record. Read more: What is a Northwest Cloudband? These changes mean that all major climate drivers affecting Australia are expected to be neutral in winter and early spring. Consequently, most of Australia is forecast to see average rainfall over the coming months. Image: Forecast rainfall anomalies for August. Areas in white are expected to be near average. See more at the Climate Page on Weatherzone. The changes that occurred in the Indian Ocean during May are a perfect illustration of the ‘Autumn Predictability Barrier’. During autumn, accuracy of climate forecasts reduces, because tropical cyclones and disturbances can disrupt the developing climate drivers. Therefore, climate forecasts produced during those months should be considered more cautiously than those produced during winter and spring. EXTREMES & RECORDS AusNSW/ACTVICQLDWASATASNT LIVE EXTREMES High Temperature Highest Temp Cocos Island Ap, WA 26.2°C (1:00AM GMT+6:30) Aug Long Term Average: 28.1°C Aug Record: 30.6°C (2022) Low Temperature Lowest Temp Cooma Ap, NSW -6.4°C (4:30AM AEST) Aug Long Term Average: -1.5°C Aug Record: -13.9°C (1994) Rain Wettest Low Rocky Point, TAS 19.2mm (Since 9am) Aug Long Term Average: 149.0mm Aug Record: 43.6mm (2013) TODAY’S EXTREMES High Temperature Highest Temp Fitzroy Crossing, WA 34.5°C (2:58PM AWST) AUG Long Term Average: 33.4°C AUG Record: 39.5°C (2020) Low Temperature Lowest Temp Cooma Ap, NSW -6.6°C (4:29AM AEST) AUG Long Term Average: -1.5°C AUG Record: -13.9°C (1994) Rain Wettest - - (24h to 9am) Long Term Average: - Record: - THIS MONTH’S EXTREMES High Temperature Highest Temp Yampi Sound (Defence), WA 35.2°C (2 August) Aug Long Term Average: - Aug Record: - Low Temperature Lowest Temp Cooma Ap, NSW -9.0°C (2 August) Aug Long Term Average: -1.5°C Aug Record: -13.9°C (1994) Rain Wettest South Johnstone, QLD 64.8mm (MTD) Aug Long Term Average: 91.7mm Aug Record: 414.3mm (1959) THIS YEAR’S EXTREMES High Temperature Highest Temp Carnarvon Ap, WA 49.9°C (18 February) JAN Long Term Average: 31.4°C JAN Record: 47.8°C (2015) Low Temperature Lowest Temp Liawenee, TAS -13.5°C (4 July) JUN Long Term Average: -1.0°C JUN Record: -11.2°C (2013) Rain Wettest Tully, QLD 4236.0mm (YTD) Annual Average: 4070.4mm Annual Record: 7898.0mm (1950) Records data is supplied by the Bureau of Meteorology and has not been independently quality controlled. WEATHER IN BUSINESS -------------------------------------------------------------------------------- 01 Aug 2024, 12:17PM AWST JULY 2024, THE WINDIEST MONTH IN A YEAR After a prolonged wind drought in Autumn, July 2024 was the windiest month in just under a year for the National Electricity Market (NEM). The slack winds in autumn were caused by blocking high pressure systems sitting over southern Australia forcing cold fronts and associated wind away from Australia. The map below shows that during autumn many parts of southern Australia saw below average wind (blue) in response to the high pressure pattern. Image: 10m wind speed anomaly (m/s) for Autumn 2024 vs climate of 1991 to 2020. Source: Climatereanalyzer During July, this stagnant weather pattern was well and truly interrupted as a long-wave trough influenced the region, sending frequent cold fronts and gusty winds over southeastern Australia The map below shows that during July 2024, wind contributed 2914 GWh/month, the windiest month since June 2023. During July 2024, the NEM also saw its windiest week since wind power originated, with wind producing 998 GWh in the week ending, July 25. The map shows that the windiest day of this week was Friday, July 19, when a strong cold front swept across the NEM. While a cold front is crossing southeastern Australia in the next 48 hours, it is not particularly strong and most likely won't bring high wind power to the NEM. The Wind Farm Output forecast for the NEM shows that wind power should be strong for several days from Thursday, August 8. Image: Weatherzone’s 14-day wind farm output forecast for the NEM. The uptick in wind power forecast during mid-August is in response to the negative southern annular mode strengthening in the Southern Hemisphere. The SAM has recently dipped into a negative phase in response to stratospheric warming above Antarctica. Forecast models suggest that further stratospheric warming will take place in the opening fortnight of August, causing the current negative SAM to get even stronger. Image: SAM (also called the Antarctic Oscillation or AAO) index observations and forecast, showing a strong negative SAM phase underway that is expected to persist into August. Some models are suggesting that this negative SAM could linger into spring, increasing wind across the NEM. However, it’s too early to know if, and how, this stratospheric warming event will continue to influence weather patterns in the Southern Hemisphere into late spring and summer. We will be keeping a close eye on the stratospheric warming and negative SAM event in the coming months, regularly updating our clients with seasonal briefings and forecasts. To find out more, please visit our contact page or email us at business@weatherzone.com.au. 22 Jul 2024, 11:17AM AWST ANOTHER WINDY WEEK There has been a major shift in the wind pattern over southern Australia, with another great wind power week on the cards. During autumn and the beginning of winter, the National Electricity Market (NEM) saw a wind drought in response to abnormally high pressure, forcing cold fronts and the associated wind south of Australia. There has been a shift in this pattern in recent weeks, with plentiful cold fronts and low-pressure systems drifting across southern Australia. This has been influenced by a long wave trough impacting Australia in recent weeks. Last week, the NEM saw its windiest week in more than a year, contributing 897 GWh/week to the grid. Image: Wind weekly contribution to generation (GWh/week) for the last year leading up to Sunday, July 21, 2024. Source: OpenNEM The cold front that impacted southern Australia late last week brought widespread damaging winds to several states and territories. This week will be windy again as several cold fronts sweep across the south of the continent. The image below shows Weatherzone’s NEM wind farm output for the next week. Image: Weatherzone’s National Electricity Market wind farm output for the next 7 days in MWH. You can see the windiest days this week are expected to be Tuesday and Wednesday, as a cold front moves across southeastern Australia. A low pressure system will then move across the Bight later this week, bringing another burst of strong winds to the region. Image: Instantaneous wind gust forecast for 1pm AEST on Wednesday, July 24, according to ECMWF. Winds are likely to reach damaging strength over parts of southeastern Australia during this week. Tas could see damaging winds impacting the state each day between Tuesday and Saturday. Meanwhile parts of SA, Vic, NSW and the ACT should see damaging winds on Wednesday and Thursday. These winds have the potential to cause cut outs, where wind turbines are turned off in strong winds to prevent damage. Most wind farms turn off the turbines if the wind speed reaches the ‘cut off’ wind speed of 90km/h (25m/s), which means that the wind power is not being harnessed. During these periods of intense winds, wind power capacities will be reduced if the turbines remain turned off. This westerly wind pattern will also bring a warm week to parts of southeastern Australia and increased rainfall over parts of southwestern WA, Tas and southern Vic and the western plains in NSW. Image: Accumulated rain forecast for the week leading up to 10am Monday, July 29, according to ECMWF The increased cloud associated with the frontal activity will reduce solar output in these areas. Looking further ahead, we should continue to see increased wind and frontal activity across southern Australia during late July and August in response to the Sudden Stratospheric Warming event. 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