10/03/2022, 4:47 am EDT

Australia Season 1-3 Ahead Outlook: Primary concern is wet in the East. Not expecting important drought risk. Climate is generally cooler than normal.

Executive Summary: The Climate Impact Company season 1-3 ahead forecast for Australia valid for October and November 2022 plus meteorological summer 2022-23 and spring 2023. The forecast is based on a constructed analog which heavily considers presence of La Nina which produces a 3rd peak (in the past 3 years) by November, negative Indian Ocean Dipole (-IOD) also likely to peak in November and presence of a marine heat wave in the subtropical ocean surrounding and east of New Zealand. The sensible weather forecast indicates patchy dry areas in Northwest Australia and on the South Coast require monitoring for potential sneaky drought. However, the greatest concern is more heavy rain in Eastern Australia into early next year. Once -IOD/La Nina ease, East wet risk ends. Climate: The August 2022 Australia soil moisture anomaly analysis from the Australia Bureau of Meteorology indicated moderate to very wet soil conditions across East and Northeast Australia plus the coastal southwest continent (Fig. 1). The official September analysis is not yet available. However, based on NOAA precipitation rate anomaly analysis for Sep. 1-29, the wet soil signature in the East certainly continues (Fig. 2). Interestingly, NOAA soil moisture analysis is agreeable with the wet conditions analyzed in the East but in disagreement with patchy dry soil areas located on the South Coast and Northwest Australia (Fig. 3). The long-term (48-month) Australia precipitation climate is wet in northwest and northeast continent and very wet in the East/Southeast (Fig. 4). The prevailing wet climate has prevented deep layer (10-200 cm) soil moisture anomaly areas which can foreshadow rapid onset of drought or flash drought. In fact, deep layer soil moisture anomalies are above normal in the East and Southeast (Fig. 5). The long-term tendency for above normal rainfall is (mostly) related to a persistent La Nina climate best demonstrated by multivariate ENSO Index vs. conventional Nino34 SSTA (Fig. 6). Most recently, the negative phase of the Indian Ocean Dipole (-IOD) has developed due to the warming of the SSTA regime northwest and north of Australia (Fig. 7). The -IOD pattern generally favors a wet climate for western and southern portions of Australia. -IOD and La Nina are wet influences on Australian climate. How long will -IOD and La Nina last? Based on the latest ECMWF global SSTA forecast for February 2023, both IOD and ENSO shift into neutral phase (Fig. 8). Climate Impact Company (CIC) expects neutral ENSO for much of the first half of 2023 and possibly onset of El Nino for later next year (Fig. 9). The CIC ENSO forecast is based on a “recharge oscillator”. Emergence of -IOD warmed the far West Pacific/east Indian Ocean tropics encouraging convective atmospheric currents taking advantage of the exceptionally warm ocean. To replace the rising air, trade winds from the east were generated which in-turn up-welled cool subsurface water near the Dateline and eastward along the equator to cause La Nina to peak for a 3rd time since 2020. Consequently, dissipation of -IOD in early 2023 coincides with a rapidly fading La Nina. Historically, there is a 2-in-3 chance El Nino follows a 3-year La Nina episode. There are many sectors of the global oceans developing mid-latitude regional warm SSTA zones known as marine heatwaves or “warm blobs”. Most prominent is the “warm blob” in the northeastern Pacific Ocean which formed in 2013. However, many other “warm blobs” have formed. The large areas of anomalous warm water are well-correlated with stronger than normal high-pressure ridge areas aloft. When these high-pressure ridge areas extend across continents drought can develop rapidly as observed in China, the U.S. and Europe during just-finished northern hemisphere summer. The Australia climate is affected by the New Zealand “warm blob”. Across this warm SSTA region a tendency for strong subtropical ridging is common during recent years. To compensate for this high-pressure ridge to the east of Australia, a tendency for an upper trough has formed on the East Coast of Australia. The presence of this trough has caused historic rainfall events at times on the Australia East Coast. As indicated in the ECMWF global SSTA forecast, the New Zealand “warm blob” continues for upcoming summertime in the southern hemisphere and could enhance La Nina wet risk for East Australia until the La Nina episode ends. Climate summary: The Australia season 1-3 ahead climate forecast is based on a constructed analog which considers presence of -IOD and La Nina into early 2023 followed by dissipation of each climate phenomena plus persistence of the New Zealand “warm blob”.   Fig. 1-3: The most recent (August 2022) Australia Bureau of Meteorology monthly soil moisture anomaly analysis, the (NOAA) September 1-29 rainfall rate anomalies and (NOAA) daily soil moisture anomaly analysis. Fig. 4-6: The long-term (48-month) rainfall anomaly analysis for Australia, deep layer soil moisture anomaly analysis and monthly ENSO phase for 2020-22 based on multivariate ENSO index (MEI). Fig. 7: A classic negative phase of the Indian Ocean dipole (-IOD) has developed in the Indian Ocean. Fig. 8: The ECMWF global SSTA forecast for February 2023 indicates both -IOD and La Nina end. Fig. 9: La Nina 2020-22 entered a 3rd year due to a recharge oscillator (evolution of the -IOD pattern). October 2022: The October constructed analog is in agreement with operational models. Indicated is a persistent upper trough centered on the southern half of Western Australia occasionally extending eastward to New South Wales. Sensible weather results include a cooler than normal climate for the southern 2/3 of the continent for mid-spring. Northern Queensland is warmer than normal. The upper trough supports a wet climate for the East Coast, most prominently near the Queensland/New South Wales state line. Parts of the North Coast are also wetter than normal.   Fig. 10-11: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for October 2022. November 2022: In November, a weak upper trough persists across central continent. An amplified ridge is forecast southeast of Australia. The forecast may be too cool eastern areas possibly warmer than indicated. Additionally, the wet forecast in the East may be wetter. Potential for an unusually warm month in Victoria. Fig. 12-13: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for November 2022. DEC/JAN/FEB 2022-23: During meteorological summer, especially the second half, the La Nina/-IOD pattern is expected to break quickly. Therefore, there may be frequent pattern changes during summertime. Wet weather should begin to ease in the East. Wet weather suppresses drought risk across the southern continent. One area to watch for sneaky drought is across the northern continent. A near to slightly below normal wet monsoon is expected this season. Fig. 14-15: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for DEC/JAN/FEB 2022-23. MAR/APR/MAY 2023: Neutral ENSO/IOD dominate by next autumn. The climate pattern favors lack of late summer anomalous warmth as a large cool anomaly is projected over west/central continent. The wet pattern in the East is easing. Dryness is dominant in the West. Fig. 16-17: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for MAR/APR/MAY 2023.