Forest Fires in the United States: 4 May 2000

Forest Fires in the United States

4 May 2000

Size of the fire: 4,000+ acres (more than 1,600 hectares [ha])
10 miles southeast of Mio, Michigan, Oscoda County, the fire started on 2 May afternoon in continuous Jack Pine fuels and driven by 15-20 mph winds exhibited running, crowning and spotting up to ¼ mile in front of the head. Several residences and cabins were threatened and some temporary evacuations were ordered. The threat to these structures has passed and evacuees have returned to their homes. By early evening the fire had grown to 3,500 acres (1,400 ha). In the morning a light rain began falling on the incident. At this time the storm is breaking up and the winds are starting to increase from the west. There are 13 engines and 11 dozer/tractor plow units working on the incident for a total of 93 personnel from the central Michigan interagency community.
General Fire Behavior in Jack Pine stands may sustain running crown fires when the needle moisture is below 125%. Currently needles moistures are averaging 97%. Relative humidity of less than 25% can result in erratic and intense crown fires. Winds greater than 15 mph pose and extreme hazard. Combinations of any of the above factors can greatly increase fire behavior. Hardwoods will exhibit less extreme fire behavior, but intense heat can lead to fast-moving fires in the hardwoods as well as the pinelands.

According to a report from William K. Stevens, Drought, Persistent and Severe, Strikes Again (published by The New York Times, 25 April 2000), much of the country’s midsection and a broad swath of its southern tier from Arizona to Florida – roughly a quarter of the territory of the contiguous 48 states in all – is already experiencing a moderate to severe drought with the peak months for drought still ahead. If long-range forecasts of below-normal rainfall and above-normal temperatures are accurate, conditions may well get worse. And as always, drought raises the risk of wildfires. Many experts believe that with the world’s climate warming as it is, droughts will become more frequent and severe. But apart from that, and regardless of whether humans are responsible for global warming, there is plenty of evidence that big, damaging droughts are inevitable. In the article was also pointed out, that global warming could also affect the size and frequency of forest fires. A recent study of charcoal layers in Yellowstone, reflecting the last 17,000 years of fire history there, found that the number of fires peaked before 7,000 years ago, a time when summers were warmer than now. The implication is that while fires would become more frequent in a warmer climate, they would also become smaller because less fuel, in the form of dead trees and forest litter, would have a chance to build up. A longtime expert on wildfire in the West stated, if the warming trend over the last century continues, as it appears it will, some really dramatic changes in fire behavior will be expected. More frequent fires will allow less fuel to build up, in time making big conflagrations like that of 1988 less probable.

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Fig. 1. Drought: Subtle onset but real impact
(Source: The New York Times)

The Wildland Fire Assessment System (WFAS) is a contribution of “The Fire Behavior Research Work Unit”, Missoula (Montana USA). The broad area component of the Wildland Fire Assessment System (WFAS) generates maps of selected fire weather and fire danger components. Fire Danger (Potential) is a normalized adjective rating class across different fuel models and station locations. It is based on information provided by local station managers about the primary fuel model, fire danger index selected to reflect staffing level, and climatological class breakpoints. Low danger (class 1) is green and extreme potential (class 5) is red.

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Fig. 2., 3. & 4. Fire Danger Forecast Maps of the United States and Alaska for 3 May (observation time) and 4 May (forecast) 2000 for the United States.
(Source: Fire Behavior Research Work Unit, Missoula)

The Keetch-Byram Drought Index (KBDI) is a soil/duff drought index that ranges from 0 (no drought) to 800 (extreme drought) and is based on a soil capacity of 8 inches of water. Factors in the index are maximum daily temperature, daily precipitation, antecedent precipitation, and annual precipitation. KBDI = 0 – 200: Soil moisture and large class fuel moistures are high and do not contribute much to fire intensity. Typical of spring dormant season following winter precipitation. KBDI = 200 – 400: Typical of late spring, early growing season. Lower litter and duff layers are drying and beginning to contribute to fire intensity. KBDI = 400 – 600: Typical of late summer, early fall. Lower litter and duff layers actively contribute to fire intensity and will burn actively. KBDI = 600 – 800: Often associated with more severe drought with increased wildfire occurrence. Intense, deep burning fires with significant downwind spotting can be expected. Live fuels can also be expected to burn actively at these levels.

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Fig. 5. Keetch-Byram Drought Index Map of the United States, 3 May 2000
(Source: Fire Behavior Research Work Unit, Missoula)

Keetch-Byram Drought Index (KBDI) by Florida’s Division of Forestry / Forest Protection Bureau
John Keetch and George Byram developed the K/B index at the Southern Forest Fire Laboratory to evaluate the effects of long-term drying on litter and duff and subsequently, on fire activity (1968). The index is based on a measurement of 8 inches (20 cm) of available moisture in the upper soil layers that can be used by vegetation for evapotranspiration. The index measure is in hundredths (0.01) of an inch of water and has a range of 0 through 800, with 0 being saturated and 800 representing the worst drought condition. The index indicates deficit inches of available water in the soil. A K/B reading of 250 means there is a deficit of 2.5 inches (64 mm) of ground water available to the vegetation. As drought progresses, there is more available fuel that can contribute to fire intensity.
For further information on the KBDI please refer to Keetch-Byram Drought Index Revisited: Prescribed Fire Applications.

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Fig. 6. Keetch-Byram Drought Index Map of Florida, 3 May 2000
(Source: Florida Division of Forestry)

Incident Management Situation Report (3 May 2000):

Current Situation:
Containment efforts proceeded on the large fires in the Southwest, Southern, and Eastern areas. Resource ordering through the National Interagency Coordination Center was minimal. Very high to extreme fire indices were reported in Arizona, New Mexico, Texas, California, Utah, Michigan, and Wisconsin.
Lower Michigan and Wisconsin will be mostly sunny with high temperatures in the 70’s. Winds will be south to southeast at 10 to 25 mph. Highest gusts will occur in northern Wisconsin.
Arizona and New Mexico will be sunny. Winds in Arizona and western New Mexico will be southwest at 10 to 15 mph. Eastern New Mexico will have southeast winds at 5 to 15 mph. Temperatures will range from the 70’s in the mountains to over 100 in the southern deserts.
Florida will be partly cloudy with a chance of showers in the north. High temperatures in the 80’s. Winds will be southeast at 5 to 15 mph.

According to the Incident Management Situation Report three categories of fires are distinguished, such as:
1. Fires*
2. Prescribed Fires
3. Wildland Fire Use Fires**

*  This classification corresponds to the category “wildland fires” as defined by the National Interagency Fire Center (NIFC)
** A brief excursion to wildland fire terminology:

Wildland Fires: Fires occurring on any tpye of vegetation, regardless of ignition sources, damages or benefits.
Wildfire: Any uncontrolled wildland fire which (1) may require suppression response, or (2) any uncontrolled wildland fire which meets management objectives and is declared as a Wildland Fire Use Fire (see below) or syn. Prescribed Natural Fire or Prescribed Fire.
Prescribed Fire: Occasionally also called management-ignited fire, or prescribed burning, is a controlled application of fire to vegetation in either their natural or modified state, under specified environmental conditions which allow the fire to be confined to a predetermined area and at the same time to produce the intensity of heat and rate of spread required to attain planned resource management objectives.
Wildland Fire Use Fire: Naturally ignited fire which is managed to achieve resource benefits under close supervision (syn. Prescribed Natural Fire)

Detailed information and data about fires, prescribed fires, wildland fire use fire and burned areas (3 May 2000) for all geographic areas of the United States can be gathered from the Incident Management Situation Report.

Long-range, 30-day weather forecasts are predicting above-normal temperatures and below-normal precipitation for the southern tier of states from southern California to Florida and throughout the Midwest (see Fig.5. 30 and 90-day forecast maps).

Tab.1. Five-Year Wildland Fire Comparison Statistics Year-to-Date for the United States (27 April 2000)
(Source: National Interagency Fire Center (NIFC)

As of 04/27/00 Number of Wildland Fires Area burnt Acres Hectars 2000 27,323 715,234 289,444 1999 29,802 578,703 234,192 1998 15,586 278,279 112,615 1997 19,465 321,192 129,981 1996 46,376 1,156,082 467,849

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Fig. 7. 30 and 90-day temperature and precipitation forecast maps (May and May to July 2000)
(Source: National Weather Service, Boise, Idaho)

Wildland Fire Season 2000 in the United States (National Interagency Fire Center)

Several regions of the country have experienced significant fire activity during the first four months of 2000. States in the South, Southwest and Midwest remain in the grips of La Niña contributing to very dry conditions and wide-spread wildland fire activity. The number of acres affected by wildland fires is more than 700,000 (283,279 ha), which is almost 200,000 acres (80,937 ha) more than the four-year average for this time of year. According to the National Weather Service, La Niña, now in its second season, is at its strongest. This event causes a wetter and cooler winter for the Pacific Northwest and drier and warmer weather for the southern tier of states. As a result, areas from southern California to Florida and into the Midwest are experiencing moderate to severe drought.

Wildland Fire Activity Throughout the Country: January – April
After two dry winters in New Mexico, conditions are severe and wildland fires are burning actively. During the third week of February two 40,000 plus acre (16,187 ha) fires were reported, one of which destroyed a structure near Ft. Sumner.
By March 9, the national level of response increased as resources from various parts of the country were sent to assist with large fires in Louisiana, Florida, Georgia, Virginia, Kentucky, Mississippi, Missouri, Indiana, and New Mexico. It is not unusual for these states to experience wildland fire activity during these early months of the year.
Florida has been especially hard hit by La Niña, and is reporting as much as a two-foot rainfall deficit in some areas. Eleven large (100 acres (40 ha) or more) fires have been reported from Florida, three of which destroyed five structures. Hundreds of small fires have ignited and been suppressed by firefighters throughout the state.
A total of 22 structures, which includes primary residences and various outbuildings, have been destroyed by wildland fires in Arizona, New Mexico, Minnesota, Florida and Oklahoma so far this year.

What the Rest of the Fire Season May Bring
The Southwest area, New Mexico, Arizona and west Texas, is in its second season of drought. Although these states have received periods of significant moisture, much of the area continues to report high fire danger. Fire managers in some areas have requested additional support to assist with anticipated fire activity this spring and early summer.
Southern states from east Texas to Florida are experiencing various degrees of drought. Recent activity has diminished, however, due to seasonal “green up,” which is a period when vegetation restores its moisture after a dormant winter. Florida has not encountered a decrease in activity, however, as dry weather patterns persist throughout the state. These conditions are expected to continue into June, which indicates continued above-normal fire activity until significant precipitation is received.
The Midwest is also reporting moderate to extreme drought conditions in several areas. Wildland fire activity is expected to be above-normal in many of those areas until “green up” occurs around mid-May.
Most of the Northwest and Rocky Mountain areas including Washington, Oregon, northern California, Idaho, Montana, Colorado, and Wyoming experienced normal to above-normal precipitation during the winter. If spring precipitation remains at normal levels, fire activity is expected to be normal in these states.
The Great Basin (Nevada and Utah) and southern California winter precipitation levels range from normal to below normal. The extent of wildland fire activity will depend on the amount of moisture received during the next couple of months.
Fire danger varies greatly throughout the country. Those who participate in recreation activities in the wildlands are encouraged to check local fire conditions and follow fire safe camping activities.

Remarks on Prescribed Burning

At this time of the year prescribed burning operations are conducted routinely.

Fire is an important natural tool for ecosystem management. It can reduce dense vegetation improving wildlife habitat and lessening the potential for large, wildfire disasters. Land managers are directed to prepare a prescribed fire/burn plan for every area of public land that can burn. Some areas require total suppression while others will benefit from a wildland fire. Those areas that will benefit from a fire can be treated by a prescribed fire.

Especially, for the moment, in the southern and southeastern regions of the United States prescribed fire activities will be carried out in the following weeks and months. In this case, fire signals on satellite images can be traced back to this kind of land management activities.

In the Prescribed Fire Position Paper of the Forest Protection Bureau by the Division of Forestry in Florida, prescribed fire activity is described as a land management application that is essential to the practice of forestry, management of wildlife, preservation of endangered plant and animal species, improvement of range conditions and reduction of wildfire damage in the wildland/urban interface areas. While there is general public and landowner concern with increased smoke, reduced air quality, and liability; the general public and landowners benefit significantly from the reduction of devastating wildfire, improved wildlife habitat and forage, preservation of endangered and threatened plant and animal species, and improved management of forest resources. The prospect of severe reductions in the utilization of this management tool is of major concern to Florida’s natural resource managers and conservationists due to the subsequent loss of derived public and private benefits. They suggest the need for legislative attention.

Another report on nation-wide prescribed burning in the U.S.A. was published in  International Forest Fire News No.19 (September 1998).

A set of photographic documents on prescribed burning techniques and objectives in the Southeast can be visited in our photo archive.

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