From late January to early February 2019, a quasi-stationary monsoon depression situated over northeast Australia caused devastating floods, killing an estimated 625,000 head of cattle in northwest Queensland, and inundating over 3 000 homes in the coastal city of Townsville. The monsoon depression lasted ~10 days, driving daily rainfall accumulations exceeding 200 mm/day, maximum temperatures 8–10 °C below normal, and wind gusts above 70 km/h. In this study, the atmospheric conditions during the event and its predictability on the weekly to subseasonal range are investigated. Results show that during the event, the tropical convective signal of the Madden-Julian Oscillation was over the western Pacific, and likely contributed to the heavy rainfall, however the El Niño-Southern Oscillation was not in the usual phase for increased rainfall over Queensland. Over the northern Tasman Sea, an anticyclone helped maintain a positive phase of the Southern Annular Mode and promote onshore easterly flow. Somewhat consistent with these climate drivers, the monthly rainfall outlook for February issued by the Australian Bureau of Meteorology on 31 January provided no indication of the event, yet forecasts, not available to the public, of weekly-averaged conditions by the Bureau's dynamical subseasonal-to-seasonal (S2S) prediction system were more successful. For the week of 31 January to 6 February the prediction system forecast a more than doubling of the probability of extreme (highest quintile) weekly rainfall a week prior to the event, along with increased probabilities of extremely low (lowest quintile) maximum temperatures and extreme (highest quintile) wind speeds. Ensemble-mean weekly rainfall amounts, however, were considerably underestimated by the prediction system, even in forecasts initialised at the start of the peak flooding week, consistent with other state-of-the-art dynamical S2S prediction systems. Despite this, one of the individual ensemble members of the Bureau's prediction system did manage to forecast close to 85% of the magnitude of the rainfall across the most heavily impacted region of northwest Queensland a week before the event. Predicting this exceptional event beyond two weeks appears beyond our current capability despite the dynamical system forecasts showing good skill in forecasting the broad-scale atmospheric conditions north of Australia a week prior.

从2019年1月下旬至2月初，澳大利亚东北部发生的准静止季风低压造成了毁灭性的洪灾，在昆士兰州西北部杀死了约625,000头牛，并在沿海城市汤斯维尔淹没了3000多个房屋。季风低压持续了约10天，导致每日降雨量累积超过200毫米/天，最高温度比正常低8–10°C，阵风超过70 km / h。在这项研究中，研究了事件发生期间的大气条件及其在每周至次季节范围内的可预测性。结果表明，在活动期间，马登-朱利安涛动的热带对流信号在西太平洋上空，可能是造成大雨的原因，然而，厄尔尼诺-南方涛动并没有进入昆士兰州降雨增加的通常阶段。在塔斯曼海北部，一个反气旋帮助维持了南环形模式的积极阶段，并促进了陆上东风。与这些气候驱动因素有些相符，澳大利亚气象局1月31日发布的2月份月度降雨量预测没有提供该事件的迹象，但该局动态的季节性反季节活动提供了每周平均情况的预报，但未向公众提供季节性（S2S）预测系统更为成功。在1月31日至2月6日的一周内，预测系统预测在事件发生前一周，每周（最高五分位数）极端降雨的可能性将增加一倍以上，以及极低（最低五分位数）最高温度和极端（最高五分位数）风速的可能性增加。但是，即使在高峰洪灾周开始时初始化的预测中，也与其他最新动态S2S预测系统一致，预报系统大大低估了集合平均周降雨量。尽管如此，在事件发生一周前，该局预报系统的一个合奏成员确实设法预报了昆士兰西北部受灾最严重地区的近85％的降雨。