Annual Fire Cycle:
Queensland’s Scenic Rim experiences a fire season driven by three primary phases:
- Fuel Growth (Summer) - Hot, humid, and wet conditions promote vegetation growth, increasing fuel loads.
- Curing (Autumn & Winter) - Rainfall declines around April, triggering slow vegetation dieback and overnight frosts accelerate fuel curing of open grasslands.
- Fire Season (Spring & Early Summer) - Hotter, drier weather arrives in spring, with westerly and north-westerly winds that can fan fire spread. Deep low-pressure cells over Tasmania correspond with the strongest westerly winds and highest fire dangers.
When the subtropical ridge migrates southward in summer, it weakens westerly winds and brings wetter conditions that end fire season and restart the cycle.
Local Weather Effects:
- Sea Breeze - During the day, land west of Boonah heats faster than the Pacific Ocean, drawing in cool, moist air, and a sea breeze typically pushes into Boonah between 5:00 and 7:00 PM.
- Katabatic Winds (Night) - When the earth cools at night, it lowers the temperature of the air immediately above; this layer of dense air then flows downslope. These Katabatic winds are strongest when:
- The sky is clear, and synoptic winds are light.
- Slopes are steep and sparsely vegetated (including burnt ground).
- Anabatic Winds (Day) - Solar heating during the day warms air near the ground, causing it to rise uphill. It is more potent than Katabatic winds, and in the Southern Hemisphere, north and west-facing slopes experience more intense solar radiation, driving later and stronger Anabatic winds.
- Bernoulli (Venturi) Effects - Wind forced over mountains and valleys accelerates airflow as the obstruction channels the flow. Meanwhile, the lee side of obstructions can experience unpredictable and turbulent flows.
Operational Considerations:
- The Bureau of Meteorology (BoM) publishes four-day fire danger ratings based on the Fire Behaviour Index for our Southeast Coast district. However, more granular fire danger forecasts are available via the Fire Danger Viewer.
- Collecting weather data in the field improves predictive modelling. The standard for wind measurement is 10m above ground; however, raise your Kestrel anemometer to as high as practical in the field. Send readings to Incident Command.
- Predictive services can also deploy calibrated mobile weather stations that send real-time measurements to BoM. When requesting a weather forecast for a specific fire, quote the incident number—this helps predictive services reference the fire’s location and refine their projections.
- Flammagenitus Clouds typically form when 4,000–5,000 hectares of coarse fuel are burning. If the atmosphere is unstable, they can develop into Cumulonimbus Flammagenitus (Pyrocumulonimbus)—fire-generated thunderstorms capable of:
- Producing downbursts—strong, erratic winds that can spread fire in any direction.
- Generating lightning strikes—potentially igniting new fires up to 100 km from the main fire front.
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