A More Difficult 100

Black Forest Fire.  Source: Colorado Springs Gazette

Wildland fire is raging once again near Colorado Springs.  El Paso County Sheriff Terry Maketa reported at 9 am this morning that at least 80 homes have burned in the Black Forest Fire, with over 7,000 homes evacuated.   

The wildfire ran more than 8 miles yesterday.  Atmospheric conditions were simply atrocious.  At the Colorado Springs Airport, temperatures yesterday afternoon reached the high 90s.  

That's bad, but the air was unbelievably dry.  At 3 PM MDT, it was 96ºF with a dewpoint of -4ºF.  That yields a dewpoint depression (the difference between the temperature and the dewpoint) of 100ºF and a relative humidity of 2%.  It doesn't get any drier than that (well, it could, but not by much).  

Winds during that period were also gusting to more than 30 miles per hour, although they reached as high as 44 miles per hour just a couple of hours earlier.  

That's pretty much a worst-case scenario for fire weather conditions.