Wildfires - September 2009


Issued: 8 October 2009

Despite the largest recorded wildfire in Los Angeles County (California) history consuming approximately 160,000 acres throughout the month, for the nation as a whole September was below average in terms of the number of fires (5,535 fires), the number of acres burned (378,523 acres), and the average acreage burned per fire (48.2 acres per fire).

September began with 21 large wildfires scorching land in 8 states.  This comprised nine fires in California, three in Utah, two each in Colorado, Oregon and Washington, and one apiece in Arizona, Hawai'i, and Texas.  By the end of the second week of September, only five fires were active (two in California, and one each in Florida, Oregon, and Montana).  Fire danger persisted in Oregon and Montana at mid–month, with three active large wildfires apiece.  While the middle of the month remained relatively quiet for large fire activity, by the end of the fourth week of September, a total of 12 large fires were active in three western states (5 in Oregon, 4 in Montana, and 3 in California).  Unfortunately, the last week in September saw a marked increase in large fire activity across the West, especially in western Montana (7 fires) and the area around Yellowstone National Park (3 fires).  As of September 30th, there were 19 active large fires in 5 states (9 in Montana, 4 in Oregon, 3 in Wyoming, 2 in Idaho, and 1 in California).

Los Angeles' Station fire, which began on August 26th, burned an estimated 160,577 acres, making it the tenth largest fire in California history since 1933.  The fire was also among the most destructive of 2009 — destroying 209 structures, including 89 homes, and claiming the lives of two fire fighters.  At its height early in the month, the fire threatened an estimated 12,000 structures, including the historic Mount Wilson observatory and dozens of critical communications towers.  According to an InciWeb report, as of September 19th just under $100 million USD had been spent battling the blaze.  Nearly 40 miles (64 km) of the Angeles Crest Highway was closed indefinitely due to fire damage, with repair estimates of $12 million USD, according to the California Department of Transportation.  At the end of the month, the fire was 98 percent contained, but continued to burn into October, making it the longest lived fire of the 2009 season to date.

2009 Wildfire Statistics

(Source: NIFC)
Year–To–Date Totals as of September 30th Nationwide Number of Fires Nationwide Number of Acres Burned
09/30/2009 70,217 5,616,706
09/30/2008 67,949 4,734,350
09/30/2007 72,944 8,226,003
09/30/2006 83,752 9,074,358
09/30/2005 53,175 8,160,688
09/30/2004 60,934 7,737,472
09/30/2003 49,180 3,167,289
09/30/2002 67,265 6,578,985
09/30/2001 63,067 3,221,391
09/30/2000 80,158 6,862,561
5–yr average
(2005 – 2009)
69,607 7,162,421
10–yr average
(2000 – 2009)
66,864 6,337,980

Statistics from the National Interagency Fire Center (NIFC) show that between September 1st and September 30th approximately 378,523 acres (153,183 hectares) were burned across the United States.  The total acreage burned during September 2009 was 370,230 acres (149,827 hectares) below the 2000–2009 average of 748,753 acres (303,010 hectares), and for that 10–year period was the third lowest September for acreage burned.  A total of 5,535 new wildfires were reported, which is 869 fewer than the 2000–2009 average of 6,404 fires.  This is the fourth fewest fires in September in the past decade.  Average fire size in September 2009 was 68.4 acres (27.7 hectares) burned per fire.  This value is 48.2 acres (19.5 hectares) per fire below the 2000–2009 average fire size of 116.6 acres (47.2 hectares) per fire.

For the period January 1st through September 30th, total year–to–date acreage burned was 5,616,706 acres (2,373,000 hectares), which was 721,274 acres (291,889 hectares) below the 2000–2009 average of 6,337,980 acres (2,564,890 hectares), and the fourth lowest amount of acreage burned for the period since 1999.  The year–to–date (January – September) number of fires was 70,217, or 3,353 fires above the 2000–2009 average of 66,864 fires.  For the third consecutive month, this ranks 2009 as the fourth highest year–to–date for number of fires over the past decade.  Combined, the year–to–date number of fires and acreage burned yields an average of 80.0 acres (32.4 hectares) per fire, relative to the 2000–2009 average of 95.0 acres (38.4 hectares) per fire.

The U.S. Drought Monitor indicated that extreme to exceptional drought conditions continued to impact southern and Gulf Coast regions of Texas in September, though some improvement was noted through the month, especially near Brownsville.  However, elsewhere, September dryness remained relatively unchanged over most regions experiencing moderate to severe drought, especially in the west, while much of Wisconsin and parts of the eastern U.S. experienced a deterioration of moisture levels during the month.  The moderate to severe drought conditions across much of California have remained relatively unchanged since the start of June.

According to the U.S. Forest Service (USFS) – Wildland Fire Assessment System, very high to extreme fire danger continued to impact the western United States at the start of September.  However, by the middle of the month, fire danger was low to moderate across most of the U.S., with only a few smaller regions of high to very high danger in the West, especially in eastern Montana.  Unfortunately, the latter half of September brought a return of very high to extreme fire danger to the southwestern U.S., from southern California across to West Texas.  However, the fire danger in eastern Montana diminished as September closed.

Ample rains across the nation in mid–September, including extremely heavy precipitation across the Southeast, helped to increase 10–hour fuel moisture levels throughout the U.S.  The large area of critically low moisture across the West was greatly constricted by the middle of September, but, unfortunately, re–expanded in southwestern regions toward the end of the month.  Despite the heavy month–end fire activity in Montana, 10–hr fuel moisture levels were relatively high across the state.  Alaska, experienced some drying during the middle of the month, but returned to high moisture levels toward the end of September.

Patterns of 100–hour and 1000–hour fuel moisture were similar to those of 10–hr fuel moisture in September — both across the coterminous U.S. and in Alaska.  In the lower 48 states, generally dry larger fuel moisture levels were present west of the Great Plains, while adequate moisture levels occurred eastward from the Plains.  In general, the highest large fuel moisture levels were in the Northeast and parts of the Gulf states.

The Keetch–Byram Drought Index (KBDI), a widely used drought index for fire risk, remained relatively unchanged across the western United States during September.  Rainfall during mid–September helped improve KBDI conditions over southern Texas.  Dangerously dry conditions, however, appeared in northern California and southwestern Oregon at the end of the month.


Citing This Report

NOAA National Climatic Data Center, State of the Climate: Wildfires for September 2009, published online October 2009, retrieved on October 22, 2014 from http://www.ncdc.noaa.gov/sotc/fire/2009/9.