Event Overview
This wildfire became the most destructive (costwise) in Colorado history.
Marshall Fire
This phenomenon allowed strong winds aloft to accelerate down the eastern slopes of the Front Range.
a downslope windstorm (mountain wave)
These ground-based measurements documented rapid increases in wind gusts and pressure drops.
surface weather stations
This high-resolution model was central to diagnosing the windstorm.
HRRR
Extreme winds alone were sufficient to produce catastrophic fire spread.
True
The event occurred on this date.
30 December 2021
A strong inversion in this pressure layer helped trap momentum before releasing it downward.
450–600 hPa
These vertical profiles revealed strengthening inversions and extreme midlevel winds.
radiosondes (weather balloons)
This diagnostic estimates how efficiently strong winds aloft can mix to the surface.
wind-gust potential (WGP)
The paper argues that deterministic models can provide uncertainty estimates by examining this.
spatial and temporal consistency
Observed surface wind gusts exceeded this approximate speed near the foothills.
~45 m s⁻¹ (about 100 mph)
Boulder County was positioned in this jet-streak quadrant, producing strong upper-level descent.
the left-rear quadrant
These provided high-frequency vertical data during peak conditions near Denver.
commercial aircraft soundings
Forecasters used repeated HRRR runs to approximate this probabilistic concept.
an implicit ensemble
This atmospheric configuration was described as rare and non-classical for Boulder.
the jet–mountain-wave coupling
The fire spread rapidly eastward into these populated communities.
Superior and Louisville
This feature formed about 10–15 km east of the foothills and marked the termination of intense downslope flow.
a hydraulic jump
Surface pressure dropped by approximately this amount as the jet shifted southward.
3–6 hPa
Once run-to-run consistency emerged, this warning was issued for lower elevations.
a High Wind Warning
The authors recommend reconsidering these operational criteria for wind-driven fires.
Red Flag Warning thresholds
Two major ignition mechanisms considered were extreme winds interacting with powerlines and this unusual underground feature.
a coal seam fire
Unlike classic Boulder windstorms, this event featured southwest flow and this unusual surface behavior.
minimal surface temperature change
This fuel condition, caused by months of drought and no snowpack, worsened fire spread.
critically dry fine fuels (grass curing)
Despite catastrophic fire behavior, this warning was not issued due to humidity thresholds.
a Red Flag Warning
The central lesson: forecasting extreme events requires integrating surface data, vertical structure, and this modeling strategy.
multidimensional interpretation of high-resolution model guidance