U.S. Wildfires 2015: Are The Worst Yet To Come?

Thus far, 2015 has been one of the worst U.S. wildland fire seasons since modern records began. More than 8.2 million acres have burned across the nation as of September 1, an area larger than Massachusetts and Rhode Island combined. Across the last ten years, that’s the largest amount of fire-scorched U.S. acreage for the January-August period, and it’s close to 50% above the decadal year-to-date average. We are well ahead of the pace set in 2007, when 9,328,045 acres burned, the highest annual total in records going back to 1960.



Figure 1. Flames from a backfire operation burn behind an emergency vehicle near the Rocky Fire on August 3, 2015, near Clearlake, California, north of San Francisco. Some 3,000 firefighters battled the Rocky Fire, which burned more than 80,000 acres and destroyed almost 100 residences and outbuildings. Image credit: Justin Sullivan/Getty images.


There’s a more complex story hiding behind these factoids. Certainly there have been some intense and large fires across the Pacific Northwest, pumping out smoke that’s reddened skies and clotted lungs across large swaths of the nation. But up until August, the main factor behind this year’s large wildfire acreage (as explained by Tom Yulsman at Discover’s ImaGeo blog) was the extent of fire in Alaska. More than 5.1 million acres had burned across the state as of September 1, most of it by midsummer. With Alaska’s fire activity now slowing down, the state’s total affected acreage will likely rank second behind 2004, when a total of 6,590,140 Alaskan acres went up in flames.

It was clear by early summer that the Pacific Northwest was in line for a potentially rough fire season, with long streches of record spring and summer heat following a winter with record-low snowpack. Simply having a parched landscape doesn’t automatically translate into big fire, though. If strong, dry winds are absent; if fires aren’t triggered by lightning and/or human activity; and/or if firefighters manage to tamp down fires quickly, then the potential for disaster may go unrealized. Wildfires didn’t begin taking full advantage of the Pacific Northwest’s primed-for-fire condition until mid-August, when the Okanogan Complex roared to life across north-central Washington. Now the state’s largest assemblage of wildfires on record, the Okanogan Complex (40 percent contained as of Tuedsay) has destroyed more than 170 homes.


Figure 2.The Significant Wildland Fire Potential Outlook for September 2015 shows above-normal risk across parts of four western states, as well as a small part of central Texas. Image credit: National Interagency Coordination Center.


On August 13, officials upgraded the National Preparedness Level for wildland fire to category 5, the highest, meaning that multiple major fires have the potential to exhaust all of the nation’s firefighting resources. This is the first category-5 ranking since a week-long stretch in August 2013, and the fifth such period in the last ten years. Cooler temperatures should continue to tamp down the fire risk in Alaska this month, but it’s far too soon for other western states to rest easy. The latest monthly outlooks for wildland fire potential, issued on Monday by the National Interagency Coordination Center, show an above-normal risk of significant wildfire in September across eastern Washington, northeast Oregon, and far northwest Montana, as well as the Sierra Nevada and coastal mountains south of the Bay Area in California. By October, the risk is expected to return to near normal over the Pacific Northwest and central California, but the highly populated belt of Southern California is still targeted for above-normal risk.

Why fall is the most-feared time for wildfire in California
California’s Mediterranean climate means that rainfall is focused in the period from late fall into spring, with the landscape then getting progressively drier until the next wet season kicks in. This sets up prime conditions for wildland fire during the typically warm, dry weather of September and October, sometimes goosed by strong offshore winds (dubbed the Santa Ana wind in the L.A. area). Late October 1991 brought the horrific Oakland hills firestorm, which destroyed more than 2,800 homes and killed 25 people, and Southern California’s record-setting wildfire seasons of 2003 and 2007 both peaked in October.


Figure 3. Meg Tallberg (left), whose home was not damaged by fire, offers her support to neighbor and friend Jenny Fratis (right), whose house (background) was destroyed in the Witch Fire, as residents returned to Rancho Bernardo in California's San Diego County on 25 October, 2007. Image credit: Robyn Beck/AFP/Getty Images.


This year, California is entering fire season after four years of drought, culminating in what’s been the warmest year for California in more than a century of recordkeeping. Although some unusual summer rains have provided dabs of relief across the far southeastern desert, much of the landscape across central and southern California remains tinder-dry. Some 46% of the state is now in exceptional drought, the highest ranking assigned by the National Drought Mitigation Center in its weekly U.S. Drought Monitor. That’s down a bit from 58% at this time a year ago, but the impacts of long-term drought in the hardest-hit areas remain severe. In August, a study from the University of California, Davis, estimated that the ongoing drought will cost California about $2.7 billion in 2015. Several intense, destructive fires have already struck the state, including the small but frightening, interstate-jumping North Fire east of Los Angeles in mid-July and the huge Rocky and Jerusalem Fires north of San Francisco in late July/early August.

The main questions awaiting the West’s fire-prone areas this autumn--questions that forecasters can’t answer with confidence--is how often and where windy frontal systems and/or strong offshore flow will materialize. NOAA’s seasonal outlook for September through November maintains above-average temperatures throughout the West Coast states, with precipitation below average in the Pacific Northwest and above average over southern California. The strengthening El Niño gives SoCal a good chance at above-average rains this winter, but the heaviest Niño-related rains often don't arrive till December/January.


Figure 4. While in Alaska, WU art director Lauren Moyer captured the not-so-common sight of a virtually cloud-free Mount Denali on August 3, 2015. In the foreground is a WU personal weather station, MEVCA2. Image credit: wunderphotographer moyerdestroyer.

Climate change and wildfire risk
One of the key points made by President Barack Obama in his visit to Alaska this week (including Wednesday’s scheduled stop north of the Arctic Circle, the first ever by a president in office) is the role of human-induced climate change in exacerbating wildfire risk across the state. In a speech delivered Monday in Anchorage, Obama noted: “Alaska’s fire season is now more than a month longer than it was in 1950. At one point this summer, more than 300 wildfires were burning at once.” The lengthening fire season in Alaska reflects a global trend: a new open-access analysis published in Nature Comunications in July found that 25% of Earth’s vegetated surface saw fire seasons grow longer from 1979 to 2013 by an average of close to 20%.



Figure 5. Areas that have experienced changes in the frequency of long fire weather seasons (at least one standard deviation above the historical average) during the period 1996-2013 compared with 1979–1996. Reds indicate areas where fire weather seasons have lengthened or long fire weather seasons have become more frequent. Blues indicate areas where fire weather seasons have shortened or long fire weather seasons have become less frequent. Image credit: Figure 3(b), “Climate-induced variations in global wildfire danger from 1979 to 2013,” W. Matt Jolly et al., Nature Communications 2013.


Alaska has warmed more quickly than the rest of the nation over the last 60 years, with annual average temperatures in Alaska climbing by about 3.0°F over the period from 1949 to 2014. The warming has come in phases, according to the Alaska Climate Research Center, with temperatures spiking in the 1970s and then plateauing at a “new normal” for several decades before a new level of warmth was hit in 2014, continuing into this year. The period Jan-July 2015 was Alaska’s second warmest in 91 years of recordkeeping, according to NOAA’s National Centers for Environmental Information. The U.S. National Climate Assessment, published in 2014, had this to say about Alaska’s evolving climate and fire risk: “Both wetland drying and the increased frequency of warm dry summers and associated thunderstorms have led to more large fires in the last ten years than in any decade since record-keeping began in the 1940s….More extensive and severe wildfires could shift the forests of Interior Alaska during this century from dominance by spruce to broadleaf trees for the first time in the past 4,000 to 6,000 years.”



Figure 6. Annual average temperature across Alaska, 1949 – 2014. Image credit: Alaska Climate Research Center.


Wildfires are the complex product of many variables, including forest management, fire suppression, temperatures and moisture, ignition sources, and firefighting practices. Prior to European settlement, gigantic fires were part of the natural ecosystems across much of North America. In a dot.earth blog post from 2013, Andrew Revkin discusses the historical context of U.S. fire suppression and its role in helping lay the groundwork for today’s megafires. Whatever factors have led to the forests we have today, their ability to burn intensely is being stoked by rising temperatures that intensify the impacts of naturally occurring drought, a point illustrated vividly this year from California to Washington and emphasized in several recent studies (including this one, published just this week in Geophysical Research Letters). There will be some inevitable randomness in the final, fateful steps (weather events, arsonists, etc.) that lead from a particular parched landscape to a devastating fire. We’re very unlikely to see the entire West in flames anytime soon (thankfully!), but it’s reasonable to expect that heat unprecedented in modern times and dried-out vegetation will sometimes lead to fires more intense and/or widespread than ever before seen by residents of a given area. With ever-larger numbers of Americans choosing to live amid western forests, and cities such as Oakland and Los Angeles adjoining fire-prone areas, the risks to life and property will only rise with time.



Figure 7. It’s a hurricane! It’s a typhoon! It’s both! Dan Lindsey (CIRA) posted this tongue-in-cheek analysis of Kilo, using a visible image from Japan’s Himiwari-8 satellite, as the storm straddled the International Date Line on September 1, 2015. Hurricanes are reclassified as typhoons when they move west across the Date Line. The Sydney Morning News asked whether Kilo should be called a “hurriphoon” or a “typhane.” Kilo was officially reclassified from Hurricane Kilo to Typhoon Kilo at 0600 GMT on September 1. Image credit: RAMMB/CIRA/JMA.


Tropics calming down
After weeks of hyperactivity, the Northern Hemisphere tropics are beginning to calm down for the time being. The 00Z Thursday morning run of the GFS model was not predicting any new tropical cyclones to develop anywhere in the world during the next seven days, though the European model was showing possible development next week of a tropical wave expected to come off the coast of Africa this Friday. This wave is expected to move westwards at about 15 mph towards the Lesser Antilles Islands; NHC did not mention this wave in their 8 am EDT Wednesday Tropical Weather Outlook. Tropical Storm Fred continues to weaken in the far eastern North Atlantic; likewise, Hurricane Jimena in the Northeast Pacific and Hurricane Ignacio in the Central Pacific are gradually spinning down. Only Typhoon Kilo is expected to resurge over the next several days. Currently almost stationary just west of the International Date Line, Kilo should gradually accelerate westward across warm waters south of a subtropical ridge, gaining strength along the way and perhaps reaching Category 4 status once again by the end of the week. Today (September 2) is Kilo’s 13th day as a tropical cyclone, and this morning's run of the GFS model predicted that Kilo would remain a tropical cyclone for at least nine more days. According to the National Hurricane Center, the longest-lived tropical cyclone in the satellite era is Hurricane/Typhoon John, which was tracked for 31 days during August and September 1994.

WU contributor Phil Klotzbach has a new post on the recent frenzy of North Central Pacific activity; see also his two-part entry on record-setting action across the Northern Hemisphere as a whole, posted on August 25 and August 28.

We’ll be back with another post on Thursday.

Bob Henson and Jeff Masters