Subseasonal forecasts of the northern queensland floods of february 2019: Causes and forecast evaluation
Journal
Atmosphere
Journal Volume
12
Journal Issue
6
Date Issued
2021
Author(s)
Abstract
During the austral summer 2018/19, devastating floods occurred over northeast Australia that killed approximately 625,000 head of cattle and inundated over 3000 homes in Townsville. In this paper, the disastrous event was identified as a record-breaking subseasonal peak rainfall event (SPRE). The SPRE was mainly induced by an anomalously strong monsoon depression that was modulated by the convective phases of an MJO and an equatorial Rossby (ER) wave. The ER wave originated from an active equatorial deep convection associated with the El Ni?o warm sea surface temperatures near the dateline over the central Pacific. Based on the S2S Project Database, we analyzed the extended-range forecast skill of the SPRE from two different perspectives, the monsoon depression represented by an 850-hPa wind shear index and the 15-day accumulated precipitation characterized by the percentile rank (PR) and the ratio to the three-month seasonal (DJF) totals. The results of four S2S models of this study suggest that the monsoon depression can maintain the same level of skill as the short-range (3 days) forecast up to 8–10 days. For precipitation parameters, the conclusions are similar to the monsoon depression. For the 2019 northern Queensland SPRE, the model forecast was, in general, worse than the expectation derived from the hindcast analysis. The clear modulation of the ER wave that enhanced the SPRE monsoon depression circulation and precipitation is suspected as the main cause for the lower forecast skill. The analysis procedure proposed in this study can be applied to analyze the SPREs and their associated large-scale drivers in other regions. ? 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Subjects
Australian summer monsoon
Extreme rainfall
MJO
S2S prediction
Subseasonal peak rainfall event
Atmospheric thermodynamics
Floods
Oceanography
Surface waters
Austral summers
Deep convection
Extended range
Forecast evaluation
Model forecasts
Monsoon depressions
North-east australia
Project database
Forecasting
Type
journal article