Today’s weather in Boulder, Colorado shows the hazards of living in the lee of a large mountain range. With a low pressure system to our east, a high pressure system to our west, and the mountains pinching the flow between them, a dangerous Chinook Wind has developed. Just as seen in February’s Photograph of the Month, these high wind events are notorious wildland fire starters; as I’m typing this post, a grassland fire is being extinguished near the city’s northern limits. A quick look at an anemometer near my studio indicates a peak gust of 91.3 mph as I’m typing this sentence, which is sure to make firefighting difficult. Often, these events begin on perfectly cloudless nights, leaving me with little to photograph. Today, a little extra moisture near the tops of the mountains allowed for a somewhat uncommon and very beautiful look at the dynamics of these powerful events. The bottom of the image shows the typical smooth wall cloud at mountain top. The highest peaks of the Rocky Mountains are tucked inside of it. The blue in the middle is the “Foehn Gap,” where the extreme downslope winds keep any clouds from forming. But what goes down, must come up. Rotors, or waves, develop over Boulder, as the air hops up and down in the wake of the Continental Divide. As the turbulent air rises, it forms the mesmerizing, broken edge of an altocumulus cloud bank, seen at the top of photo.
A wildland fire (or “wildfire”) is composed of many ingredients. Of course, dry fuels are essential. The Colorado Front Range foothills have plenty of these in almost any year, and almost any time of the year. But fuels are harmless without a spark. Unfortunately, today’s modern world provides ample ignition sources, from electrical wires to cigarettes to hot exhaust pipes. That being the case, wildland fires are relatively common in this dry, populated place. For a fire to grow and become uncontrollable, still more ingredients are necessary. ”Cover” was taken during Colorado’s worst fire in history, which began as an accident from an artificial ignition source, and was made worse thanks to some unfortunate geography. The leeward sides of mountain ranges are notorious for high wind events. Gusts to over 100 mph are common during these events, and the resulting infernos can be unstoppable. Wildland firefighting crews can quickly be overwhelmed in such instances. The “seasoning” in this terrible oven is dry air. Relative humidity values below 20% are also common during downslope wind events. Within just hours, this dry air can desiccate healthy vegetation that would otherwise offer some resistance to the flames. All together, this geography’s ingredients truly make a recipe for disaster.
Fire photography is always a tricky business. One way or another, wildland fires can find ways to make your life miserable. Smoke inhalation has probably been the most significant hazard for me over the years, and I’ve learned to take it seriously. We’re just beginning to discover how dangerous some of the toxic chemicals within the smoke really are. On the other hand, smoke can be extremely photogenic. This shot was captured with a normal focal length lens on a digital SLR camera with no tripod and no filters. In fact, this image is straight from the camera with no post processing; I couldn’t imagine a way to “improve” it, so I left it alone. Ironically, I was scheduled to give a lecture on wildland fire hazards this afternoon, so I only managed around a hundred shots before I had to leave. In the top center of the photograph you would usually see the Denver skyline. As such, “Cover” seemed an appropriate title.
