Wildfire 101: Fire Anatomy

Wildland firefighters use very specific terminology to describe the various parts of a fire.  The fastest-moving portion is designated the “head” of the fire, the sides of the fire are known as the “flanks”, and the slowest moving portion is known as the “tail” or “heel” of the fire. The origin of the fire is usually near the heel. A “finger” is a small area that is protruding from the main body of the fire, and may previously have been the head before a wind shift caused the fire to spread in a different direction.

Depending on the fuel and its arrangement, the head typically has the greatest flame length, flame depth, and rate of spread. This is also where the most active attack on the fire takes place.

The flanks of a fire burn outwards into the unburned vegetation. This results in the flanks having less alignment with the wind than the head, normally reducing their intensity and rate of spread. Flank fire intensity nearest the head is higher, particularly where the flanks meet the head which is known as the shoulder.

The rear portion of a fire is called the tail or heel, and is where there is the least amount of fire spread. Usually the flames at the tail are being bent towards the already-burnt fuel. The tail or heel is potentially the slowest moving part of a fire with the shortest flame length. Tail fires usually demonstrate low amounts of fire activity, but present a significant risk if they burn into areas that are more supportive of increasing fire behavior.

An “island” is a portion of unburned fuel that is inside the “black” (burned area) of an active fire. This often occurs when there are high moisture levels in that area,  or when the type of fuels or the topography of that area do not lend themselves to burning.  

“Spotting” occurs when the burning embers of fuel are carried upwards by wind and then distributed amongst the areas of unburnt fuel ahead of the main fire. The area immediately under the smoke plume is particularly vulnerable to spotting, although embers can be carried considerable distances and result in significant secondary fires. Spotting can break control lines or threaten the escape routes of ground personnel working the fire.

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Parts of a fire. Image courtesy of Becoming an Air Tanker Pilot.

 

NASA’s JPL announces plan for more advanced wildfire detection by 2018

NASA’s Jet Propulsion Laboratory (JPL) has been refining a concept first proposed in 2011 for a network of space-based sensors called FireSat that would revolutionize the monitoring coverage of wildfires globally.

 

JPL's rendering of FireSat in action

According to the JPL, “FireSat would be a constellation of more than 200 thermal infrared imaging sensors on satellites designed to quickly locate wildfires around the globe. The FireSat sensors would be able to detect fires that are at least 35 to 50 feet (10 to 15 meters) wide, within an average of 15 minutes from the time they begin. Within three minutes of detecting a fire from orbit, FireSat would notify emergency responders in the area of the fire, improving support for time-critical response decisions.” Currently MODIS and VIIRS satellites (which both serve many other functions than fire detection) operated by NASA have fire detection capabilities but are limited to large image sizes and can only detect fires twice a day. FireSat sensors would complement these systems by enabling faster, nearly continuous communication with the ground by sending low-resolution images of detected fires every minute along with a latitude and longitude of the location.

 For more on this and other stories from NASA’s JPL visit the JPLNEWS page.

California’s Fire Potential Outlook for December

 

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Southern California:

Normal significant wildland fire potential is expected for Southern California for the outlook period.

Weather and Fuels:

After a relatively wet early October, the weather over much of the area turned warmer and drier during the second half of October and into November. A strong ridge of high pressure over the Eastern Pacific kept the storm track well to the north. At the same time, several troughs to the east of the state allowed periodic offshore wind episodes to occur. Most of these were of light to moderate intensity and of short duration. Some wetting rains and high elevation snowfall occurred over portions of Central California, but most of Southern California saw little precipitation during the second half of October into the first half of November. The combination of offshore winds and warm ocean temperatures pushed many locations across Southern California into monthly maximum temperatures records. Fuel conditions vary from seasonally wet to extremely dry across the area. Most of the Sierras and higher elevations of the mountains of Southern California have seen several significant precipitation events, and with the short daylight hours and low sun angle, it would be difficult for these areas to see any additional significant fire activity this year and into early 2016. However, the dry weather allowed for a recent grass crop to cure across portions of Southern California. In general, eastern Santa Barbara County southward to Orange County are the driest parts of the area. These areas continue to see very low dead fuel moisture due to the very warm and dry weather.

Long range models depict a change in the weather pattern over the next few weeks. A much more progressive pattern seems to be shaping up over the Pacific. Additionally, the El Niño over the Eastern Pacific is likely peaking in intensity. As the east to west trade winds continue to weaken and convection increases across areas of the Eastern Pacific, storm frequency should increase in December. Significant and potentially heavy rain will accompany some of these storms. Large fire potential should be near normal early in December over the remaining dry areas.

Northern California:

Normal significant wildland fire potential is expected for Northern California for the outlook period.

Weather and Fuels:

November precipitation ranged from 50 to 125 percent of normal over most of northern California, with temperatures that were near normal to 5 degrees below normal. This helped get the early phases of a high-elevation snowpack get started. Fire Danger / Potential was down to near zero in the Northwest quarter of the Geographic Area and the roughly once-per-week storms elsewhere, each with light to moderate precipitation, sufficiently to greatly reduced fire potential.

For December, near-normal precipitation is expected, with temperatures near to a little above normal. The strongest El Niño in 18 years will affect the jet stream patterns, such that it is expected that northern California will have a good chance of receiving above normal precipitation for the three month period from January through March. Higher elevation snowpack should be the best in at least the past several years, and mid-elevations will see some snowpack (in contrast to the past two winters when there was very little).

http://www.nifc.gov/nicc/predictive/outlooks/monthly_seasonal_outlook.pdf
 

Top Ten Things You May Not Know About Wildland Fires

 

1) 90% of wildfires are human-caused

Sources of anthropogenic wildfires are most often accidental ignition by campers, hikers, or garbage/debris burns…but some are purposely started by arsonists..

2) But the majority of acres burned comes from lightning ignitions

Because they often occur in isolated locations with limited access, lightning fires burn more total acres than human-caused starts. The average 10-year total of U.S. wildfire acres burned by human cause is 1.9 million acres; 2.1 million acres burned are lightning caused. If a lightning fire is not endangering life or property, the US Forest Service will allow the fire to burn under the Fire Use Guidelines.

3) Prolonged drought plus a freeze event can prompt wildfires in non-typical seasons. 

When a freezing weather event hits a wildfire-prone area during drought conditions, it can dry fuels to the point of extreme ignitability. Despite low temperatures, wildfires can frequently still burn when these conditions exist. 

4) Aircraft don’t put out the fire, they slow the rate of spread

Though news outlets heavily cover firefighting aircraft during a wildfire, the retardant these planes drop will rarely extinguish the flames. The retardant is designed to slow the fire’s rate of spread so as to allow ground forces enough time for a direct attack. Retardant is a fertilizer-based product that is able to adhere to vegetation, requiring more heat for ignition. The fertilizer is colored red for higher visibility to tanker pilots to see where the last drop was placed.

5) Smoke color depicts fire fuel types

Smoke is the biproduct of the fuels it is burning, and the color of the smoke is often used as an indicator to firefighters of the type and density of the fuels that are involved. White smoke generally indicates light flashy fuels such as grass or twigs. Thick black smoke indicates heavy fuels that are not being fully consumed. At times thick black some can be an indicator that a manmade substance is burning such as tires, vehicles or a structure. Grey smoke can indicate that the fire is slowing down and running out of materials to burn.

6) The Story of Edward Pulaski

Edward Pulaski was a Forest Ranger in Wallace, Idaho, and is most known for saving the lives of 40 men during the Great fire of 1910. When the fire broke out of control and overwhelmed his crew, he directed his men into a cave and held them at gunpoint so they wouldn’t leave. After the fire had passed, the men came to the entrance to find the ranger covered in debris and thought he was dead. Pulaski arose and stated “Like hell I am.” A firefighting tool pulaski tool he designed was later named after him and is still used today.

7) Post-wildfire mudslides are common

A fast-moving, highly destructive debris flow can occur within a few years after wildfires scorch the soil and roots of vegetation in a particular area, especially in steep terrain. Most occur in response to high intensity rainfall events and are particularly dangerous as they sometimes happen with very little warning.

8) Peshtigo Fire in 1871 killed over 1,200 people

On October 7th, 1871, the most devastating US wildfire started in Peshtigo, Wisconsin. 1,200 people were confirmed killed and the entire town of Peshtigo was destroyed. The fire started when several small burns grew out of control due to high winds. The fire eventually burned over 1.2 million acres. This is the highest recorded death total for a wildland fire.

9) Wildfires are important for the forest ecosystem

Forest ecosystems depend on wildfires to thin the forest canopy allowing saplings near the forest floor access to sunlight. Some plants and trees require fire and heat in order for their seeds to germinate. Fire can eliminate certain plants while allowing fire-resistant species to survive and thrive.

10) Large wildfires are capable of creating their own localized weather

Wildfires generate their own winds as they grow in size. These winds will pull air into the fire as they burn more fuel. Intense heating of air from the surface induces convection, which causes an air mass to rise above the fire and, in the presence of moisture, can form pyro cumulus clouds.

 

Sources include: The History Channel, Wikipedia, Accuweather, Smokey Bear, USGS, about.com, & Spokane Chronicle

 

Black Friday Brushfires

On Friday January 13, 1939, Victoria, Australia suffered one of the worst wildfires in history. These fires came to be known as the Black Friday brushfires. They burned nearly 5 million acres and 71 people lost their lives after several towns were destroyed.

Prior to Black Friday, Victoria had experienced a long, dry, and hot summer coupled with a drought that had lasted several years. Many creeks and rivers had dried up and high temperatures and hot winds had left the forest floors extremely dry. Several small fires were already burning since December. Some of these fires could not be extinguished while others were left unattended to burn under “controlled” conditions. However, high temperatures combined with strong northerly winds on Friday the 13th strengthened these fires causing them to combine into a massive fire front which swept over the mountains into Victoria. Over 1,000 homes were burned, and the towns of Narbethong, Noojee, Woods Point, Nayook West, and Hill End were completely destroyed. The fires had burned for three days when the area was hit with heavy rains Sunday evening which eventually extinguished the blaze.  

After the fires, the Australian Royal Commission attributed blame for the fires to careless burning, such as those used for campfires and land clearing. The Commission made a number of recommendations to improve forest management and safety, such as the construction of fire towers and access trails. It also encouraged the creation of a fire administration which would be responsible for supervising controlled burns. The Black Friday brushfires contributed directly to the passing of the Forests Act, which gave the Forests Commission responsibility for wildfire protection on public land.

 

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The town of Woods Point after the Black Friday brushfires.

Image courtesy of the Victoria State Government

This Week in 1956: Inaja Fire Tragedy

On November 24th, 1956, a wildfire began on the Inaja Reservation near Julian in East County, San Diego that would kill eleven firefighters and change the landscape of wildland firefighting. 


On the night of November 25th, firefighters were attempting to cut a control line around the fire in San Diego Canyon.  They were quickly forced to retreat up an 1,100 foot ascent however, as the fire engulfed the upper canyon area above them in a mere twenty minutes, according to the official report of the fire. Eleven firefighters were trapped just below a small bluff near the top of the canyon when a “flashover” lit 40 acres of wildland all around them, effectively cutting off all safe paths of exit.  A flashover occurs when all surfaces and objects within a space have been heated to their ignition temperature, and flame breaks out almost at once over the given area.

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Inaja Fire Map, Cleveland National Forest, November 1956.

Following this unfortunate tragedy and other fatal situations going back several years, changes were made in training and tools as well as standard operation procedures during what are termed “mass fires”. Calls came for more sophisticated fire behavior training and in-depth fire behavior research for fires in difficult topography.  Policies were implemented to require experts on scene to assist in decision-making, and incentives were provided to enable wildland crews to recruit and retain the competent individuals required to perform this difficult job.  

What Warrants a Red Flag Warning from the National Weather Service?

Another Red Flag Warning was issued for Southern California late last week for very low humidities and strong offshore winds. But what factors actually warrant this official notice from the National Weather Service and what do the associated weather conditions mean?

A Red Flag Warning is used by the National Weather Service to inform area firefighting and land management agencies that conditions are ideal for wildland fire combustion and rapid spread. Specically, the warning denotes a high degree of confidence that weather and fuel conditions meet the ‘Red Flag Event’ criteria in place for a given fire weather zone. These criteria involve low relative humidity, strong winds, dry fuels, or any combination thereof.

According the the NWS, a Red Flag event is verified when the weather and fuel conditions are met simultaneously for any three hour period, and the warning remains in effect until the critical fire weather pattern ends. The characteristics of fire weather zones differ greatly across wildfire-prone areas.  Therefore the specific thresholds needed to meet the warning criteria can vary as well, based on the local vegetation type, topography, and distance from major water sources.  

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 Southern California’s Ventura and Los Angeles Counties had a Red Flag Warning in effect for below 15% RH and gusty winds.

 

Red Flag Warning Criteria From Regions of California.

(source: SoCal GACC) http://gacc.nifc.gov/oscc/predictive/weather/myfiles/Watches_and_Warnings_for_California.htm

Area Description

NWS Fire Weather Zones

Criteria

Southern California desert area excluding the Colorado River Valley

226-228, 230, 232, 260­, 262

Relative Humidity  ≤ 15% and wind gusts GTE 35 mph for 3 hours or more

Colorado River Valley

229,231

Relative Humidity ≤ 15%, with sustained winds (20 foot) ≥ 20 mph and/or frequent gusts ≥ 35 mph for 3 hours or more

Antelope Valley and SE Kern County Deserts

298, 299, 259

Relative Humidity ≤ 15% and sustained (20-foot) winds ≥ 25 mph for a duration of 8 hours or more

Southern California from mountains westward

234-258, 288-297

Either
Relative Humidity ≤15%, with sustained winds ≥ 25 mph and/or frequent gusts ≥ 35 mph (duration of 6 hours or more)

Or
Relative Humidity ≤ 10% (duration of 10 hours or more) regardless of wind

Northern California East of Cascade/Sierra Crest and Western Great Basin including the Modoc Plateau

214, 270-273, 278, 284, 285

Tahoe Management Basin: Three hours of wind gusts ≥ 30 mph and Relative Humidity ≤ 20%

Other Regions:
Three hours of wind gusts ≥ 30 mph and Relative Humidity ≤1

 

The DC-10 Very Large Air Tanker (VLAT)

Aerial firefighting involves the use of aircraft–both fixed-wing and rotary-wing–to combat wildfires. Among the fixed-wing type are air tankers and water bombers equipped with tanks that can be filled with fire retardant or water. Some air tankers (like the DC-10 VLAT pictured below) are loaded on the ground at an air tanker base, while other aircraft (such as the Bombardier 145 “Superscooper”) can be loaded by skimming water from lakes, reservoirs, or large rivers.

The DC-10 VLAT is a converted McDonnell Douglas DC-10 commercial airliner. It’s a three-engine, wide-body aircraft that was first introduced in 1971 and was in service with American Airlines, Hawaiian Airlines, and Pan Am. Production of the DC-10 ended in 1989 and the aircraft flew its last commercial flight in February 2014.

In 2002, the company 10 Tanker Air Carrier began proof-of-concept testing of the DC-10 VLAT in an aerial firefighting role. In 2006, the aircraft was issued a Supplemental Type airworthiness certificate by the FAA which allowed it to be modified for aerial firefighting. Shortly thereafter, the DC-10 VLAT was certified as an air tanker by the United States Forest Service and was first used in California during the 2006 wildfire season on a “call-when-needed” basis at the price of $26,500 per flight hour.

The DC-10 VLAT is not used on all fires as it is operationally limited due to its time to reload retardant and refuel at air tanker bases. However, one retardant drop from the DC-10 covers a swath roughly 300 feet wide and one mile in length, four times the coverage of any other tanker currently in use.

 Aircraft Specifications:

  • Cruising speed:  520 knots
  • Feet-per-minute climb rate:  2,000
  • Fire suppressant tank capacity:  11,600 gallons

**DC-10 VLAT during a demonstration for LA County Fire officials in 2006**

Ready, Set, Go!

Although there is currently no national standard for wildfire preparedness and potential evacuations, most agencies have adopted CalFire’s Ready, Set, Go! program. This program educates homeowners on ways to be prepared prior to an event and how to handle themselves during potential and imminent evacuation situations. 

READY

Before an event, prepare by designating and creating your home’s Defensible Space Zones, which are the buffer between a house and the grass, trees, shrubs, or any wildland area that surround it. This space helps to slow the spread of wildfire and decreases the liklihood your home catches fire.  It also helps protect the firefighters protecting your home.

More info on defensible space

SET

As fire season approaches, take the time to complete the 3 steps of being set for a wildfire: 

  1. Create a Wildfire Action Plan that includes evacuation planning for your home, family and pets.
  2. Assemble an Emergency Supply Kit for each person in your household.
  3. Fill-out a Family Communication Plan that includes important evacuation and contact information.

GO

Being ready to go means knowing when to evacuate the area and what to do if you get trapped. Waiting longer to leave can not only increase the chances of being trapped, it can also cause problems for emergency personnel who are attempting to access the area in order to protect homes within the community.

The Waldo Canyon fire from 2012 is a good example of Ready, Set, Go! at work. Many homes had good defensible space that either left them standing or helped fire crews save them.
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 Evacuations Map produced by RedZone Disaster Intelligence during the early stages of 2012’s Waldo Canyon Fire near Colorado Springs, CO.

With Red Flag conditions and changing wind directions that fateful Tuesday, it was crucial that residents were prepared, and that they evacuated ahead of the extreme fire behavior that destroyed 346 structures. Over 32,000 residents in the greater Colorado Springs area were evacuated during this incident.

For more detailed information on Ready, Set, Go!, see CALFIRE’s page: http://www.readyforwildfire.org/.

 

November Wildfire Potential At or Returning to Normal

As the ‘typical’ fire season comes to a close, the National Interagency Fire Center is forecasting below-normal, normal, and returning-to-normal autumn conditions across the U.S.

The only area not already at or below normal fire potential is Southern California’s coast which remains in a drought but is predicted to return to normal by the end of the month.

 Image by NIFC – Predictive ServicesNovember 2015 Fire Potential

So far the fall season has brought a few significant rain events coupled with high tropical activity in the Eastern Pacific. Heavy rain fell in Texas and in the Southeast U.S. leading to below-normal fire potential in those now-soggy areas. The approaching El Niño has a high probablity of continuing into the Spring of 2016 and keeping conditions wet in the Southern U.S. and most notably in drought-stricken California where normal fire potential is predicted to resume for the next three months. 

The full NIFC Fire Potential Outlook can be found here.