Forecasting the extreme rainfall, low
temperatures and strong winds associated with the northern Queensland floods of
The weather and associated floods that
occurred in northwest Queensland in February 2019 were responsible for the
death of 625,000 head of cattle, 48,000 sheep and flooding of over 3,000 homes.
The monthly rainfall outlook for February that was issued on January 31st
predicted a 45-55% chance of exceeding the median monthly rainfall. There was
less than a 15% chance of more than 300 mm in February. More than 600 mm of
rain fell over 10 days in inland locations.
Researchers at the University of
Southern Queensland and the Bureau of Meteorology have investigated the climate
drivers behind the event and how the forecast could have been improved. Typical
drivers of climate in Australia, such as El Niño and the Indian Ocean dipole did not play a role in this event. The
most predictable driver showing a clear influence was the Madden- Julian
Oscillation (MJO). The MJO is a large-scale eastward moving 'pulse' of cloud and
rainfall near the equator which leads to higher
rainfall over northern Australia when located over southeast Asia and the
western Pacific in summer.
The communicated forecast from the 26th
of January was initialised up to 8 days beforehand and did not predict the
event. However, applying the same methods closer to the time of the event
improved the prediction. Initialising a week prior to the event resulted in a
forecast with a 70% chance of high rainfall and similarly improved predictions
of low maximum temperature and high windspeeds. Two weeks in advance the
prediction was also improved, but to a lesser extent. The results suggest that
multi-week forecasts can fill the gap between daily weather forecasts and
monthly-seasonal outlooks, providing critical lead time for farmers to prepare
for extreme weather events.