Subtropical Foehn Winds, Southeast Queensland, Australia

Foehn winds have been a focus of research in mid-latitude mountainous regions for more than 150 years, where their onset is typically associated with warm, dry, and gusty winds. This research has now extended into high latitude regions, yet research of foehn winds in subtropical and tropical regions remains scarce. Here we present results from the first investigation of foehn winds in the subtropics of Southeast Queensland (SEQ), Australia. Analysis of meteorological records found that foehn winds occur throughout the year with peak frequency and duration in late winter (August) associated with the passage of shortwave troughs over southern Australia. Modeling of wind fields and atmospheric boundary layer conditions for three case studies was conducted using the Weather Research and Forecasting (WRF) model. Results showed foehn events in SEQ can be associated with mountain waves and hydraulic jump features in the lee of topographic barriers. Over lee slopes, acceleration of wind speeds and topographic channeling of foehn winds was found to occur, along with substantial increases in air temperature, and decreases in relative humidity. Warming of the foehn airstream is believed to occur primarily through isentropic drawdown with a likely contribution from surface sensible heat flux. Recommendations for future research are made in light of the importance of foehn winds to wildfire management and mitigation in SEQ. Foehn winds form as airflow associated with the passage of large-scale weather systems descends over the lee slopes of mountains and escarpments. These warm, dry, and gusty winds significantly change the meteorology in the lee of mountains and escarpments causing increases in air temperature, wind speed and decreases in humidity. While foehn winds have been a focus of mountain meteorology in mid-latitude regions for more than 150 years, research of foehn in other climate zones is scarce. Here we present results from the first investigation of foehn winds in the subtropics of Southeast Queensland (SEQ), Australia-a region where foehn winds significantly increase the threat of wildfires. Results show that foehn winds in this region are most common in late winter (August) with the passage of shortwave troughs over southern Australia. Using the Weather Research and Forecasting (WRF) model we find that foehn wind events in SEQ may be associated with mountain waves and other dynamical features in the lee of topography. We suggest avenues for future foehn wind research in SEQ given their importance to wildfire management and mitigation. Subtropical foehn winds are accurately modeled using the Weather Research of Forecasting model Foehn warming of +10 to +14 degrees C was simulated and caused by isentropic drawdown Modeling showed mountain wave and hydraulic jump features in trans-barrier flow