“Sing a song of seasons!
Something bright in all,
Flowers in the Summer
Fires in the Fall!”
– Robert Louis Stevenson
The “fire” in this poem, no doubt, refers to a bonfire. In many parts of the country, people gather around one for its warmth and to celebrate autumn. We aren’t so fortunate in the southwest, where fires bring destruction and loss of lives. This week’s weather conditions, in addition to other factors, were a perfect example and justification for the sense of dread we feel at this time of year. Monday and Tuesday were hot and dry as temperatures climbed past 100 degrees and the humidity dropped to a low 12%. Not wanting to be left out, the Santa Ana winds, though mild, joined in also. But this is not the making of a party, but quite the contrary a – wildfire.
As I finish writing this, the skies are clear and hot NE winds blow. The Southern California Wildfire Hazard Center, with input from NASA, universities, researchers and the L.A. County Fire Department, has developed a simple triangle diagram. Weather – Terrain – Fuel form the three points with HAZARD in the middle.
The weather component speaks for itself – high temperatures preheat the brush and wind gives fire extra oxygen and pushes the flames ahead. The complex topography or terrain of Southern California provides an inviting, but often dangerous, place for us to live. Since fires burn uphill quickly, our steep slopes contribute to rapid fire spread. The canyons channel Santa Ana winds from the Great Basin to Southern California, compressing, drying (and heating) the air as it passes though the narrow valleys. The varied topography – ridges, saddles, draws and valleys – create erratic wind conditions making fire control difficult. When a fire does occur, it frequently burns intensely because a century of total fire suppression has allowed extra tons of live and dead brush – fuel – to accumulate.
In the past, before modern fire suppression, annual fires burned here and there creating a patchwork of old and new fuels which tended to limit the spread and intensity of wildfires. These factors contribute to the extreme fire danger which occurs every autumn in the wild land/urban interface. This year, hopefully rains will arrive early and alleviate potential disasters.
The local climate dictates to the activities of its inhabitants. Our area is definitely not a good choice for an autumn bonfire. That’s okay – some origins are rather creepy. In ancient times, the Druids would slaughter and prepare livestock for the upcoming winter months. The bones (bon) were heaped and burned (fire) in celebratory ritual.
On a lighter note, nowadays autumn leaves and the remnants of summer gardens are raked together to create a fire and fun.
A low pressure is moving in bringing much cooler weather (at last!). For this weekend and upcoming week, daytime highs are not expected to exceed 80 degrees with nights around 60 predicted. Oh, there is a slight chance of rain on Tuesday.
Where is that umbrella?
Sue Kilpatrick is a
Crescenta Valley resident and
Official Skywarn Spotter for the
National Weather Service. Reach her at firstname.lastname@example.org.