— W —

Walk Test
The walk test is designed to determine the ability to carry out light duties. It consists of a one-mile test with no load that approximates an aerobic fitness score of 35. A time of 16 minutes, the passing score for this test, ensures the ability to meet emergency and evacuate to a safety zone.
see also: Work Capacity Test

Warm Front
The leading edge of a relatively warm air mass which moves in such a way that warm air replaces colder air that moves away from a region. Winds associated with warm frontal activity are usually light and mixing is limited. The atmosphere is relatively stable when compared to cold front activity.

Water Bar
A shallow channel or raised barrier, e.g., a ridge of packed earth or a thin pole laid diagonally across the surface of a road or trail so as to lead off water, particularly storm water. (Frequently installed in firelines on steep slopes to prevent erosion.)

Water Expansion Pumping System (WEPS)
Apparatus utilizing an air compressor and positive displacement pump coupled to the same engine, plumbed to a non-pressurized tank, for producing foam. The operation involves injecting compressed air into a liquid stream containing a suitable foaming agent.

Water Expansion System (WES)
Apparatus utilizing a pressurized tank, hose, and nozzle for producing foam by injection of compressed air or gas into a liquid stream downstream from the pumping source. The liquid stream must contain a suitable foaming agent.

Water Hammer
A force created by the rapid acceleration or deceleration of water, commonly created by opening or closing a valve too quickly. Pressures developed in a water hammer, proportional to the mass multiplied by the square of the velocity, can damage a pipe or hose.

Water Resources Specialist
Person responsible to the planning section chief for collecting information of water resources in and adjacent to the incident area, determining water use requirements of firefighting resources, and providing input to the Incident Action Plan about available water resources and/or anticipated shortages.

Water Source
Any strategically located supply of water that is readily available for pumps, tanks, trucks, helicopters, or fire camp use.

Water Supply Map
A map showing location of supplies of water readily available for pumps, tanks, trucks, camp use, etc.

Water Tender
Any ground vehicle capable of transporting specified quantities of water.

Water Thief
A type of bleeder valve designed for installation at convenient points in hose lines to permit drawing off water for filling backpack pumps or other use without interfering with pump or nozzle operation.

Wave
A disturbance that transfers energy from one point to another point and may take the form of a deformation of pressure or temperature. In the atmosphere such disturbances may result in major storms or merely result in changes in cloud, wind and temperature conditions. Development of a wave on a front usually slows the advance of the front due to transfer of energy to the wave development and movement.

Weather Advisory
In aviation forecasting, an expression of hazardous weather conditions not predicted in the zone weather forecast, as they affect the operation of air traffic.

Weather Information Management System (WIMS)
A centralized weather data processing system at which daily fire danger ratings are produced.

Weather Observer
Person responsible to the situation unit leader for collecting current weather data and information at the incident and providing them to an assigned meteorologist, fire behavior specialist, or the Situation Unit Leader.

Weighted Monthly Occurrence
Part of the National Fire Danger Rating System (NFDRS). Number used to determine seasonal risk class for a protection unit, calculated by multiplying peak monthly average by two and adding seasonal monthly average.

Western Regional Climate Center (WRCC)
One of six NOAA regional climate centers in the United States at which all hourly observations from all RAWS and many AWS are archived.

Wet Foam
A low expansion foam type with few and varied bubbles and rapid drain time which is used for rapid penetration and fire extinguishment.

Wet Line
A line of water, or water and chemical retardant, sprayed along the ground, and which serves as a temporary control line from which to ignite or stop a low-intensity fire.

Wet Storage
Fire retardants mixed with water and stored in tanks at air attack bases for immediate use by air tankers.
see also: Dry Storage

Wet Water
Water with added chemicals, called wetting agents, that increase water’s spreading and penetrating properties due to a reduction in surface tension.

Wet-bulb Depression
The difference between the wet and dry-bulb temperatures recorded by a psychrometer; used in conjunction with the dry-bulb temperature as a measure of the relative humidity of the air.

Wet-bulb Temperature
The lowest temperature to which air can be cooled by evaporating water into it at a constant pressure when the heat required for evaporation is supplied by the cooling of the air. It is measured by the wet bulb thermometer, which usually employs wetted wicking on the bulb as a cooling (through evaporation) device.

Wet-bulb Thermometer
In a psychrometer, the thermometer with its bulb covered with a jacket of clean muslin which is saturated with distilled water before an observation.

Wetting Agent
A chemical that when added to water reduces the surface tension of the solution and causes it to spread and penetrate exposed objects more effectively than the untreated water.

Wetting Rain
A widespread rain that over an extended period of time significantly reduces fire danger. One-tenth of an inch may be sufficient to reduce fire danger in grass fuel models. One half inch may be necessary for timber fuels under closed canopies.

Wheelbase
The distance from the centerline of the front axle to the centerline of the rear axle. For a tandem rear axle vehicle the center line is midpoint between the centers of the two rear axles.

Widow-Maker
A loose limb or top or piece of bark lodged in a tree, which may fall on anyone working beneath it.

Wildfire Suppression
An appropriate management response to wildfire, escaped wildland fire use or prescribed fire that results in curtailment of fire spread and eliminates all identified threats from the particular fire.

Wildfire
An unplanned, unwanted wildland fire including unauthorized human-caused fires, escaped wildland fire use events, escaped prescribed fire projects, and all other wildland fires where the objective is to put the fire out.
see also: Uncontrolled Fire
see also: Wildland Fire

Wildland Fire Assessment System (WFAS)
An internet-based information system, providing national views of weather and fire potential, including national fire danger and weather maps and satellite-derived greenness maps.

Wildland Fire Implementation Plan (WFIP)
A progressively developed assessment and operational management plan that documents the analysis and describes the appropriate management response for a wildland fire.
see also: Implementation Plan

Wildland Fire Investigator (INVF)
An individual responsible for identifying and securing a wildfire’s origin and determining the probable cause and documenting causal factors in a case report. INVF may not be directly assigned to an incident, working in conjunction with incident management as not to interfere with incident operations, while ensuring that an incident does not impede the on-scene investigation.

Wildland Fire Leadership Principles
Eleven principles describing tangible behaviors that reflect and demonstrate the wildland fire leadership values. The eleven principles are: 1. Be proficient in your job. 2. Make sound and timely decisions. 3. Ensure tasks are understood, supervised, and accomplished. 4. Develop your subordinates for the future. 5. Know your subordinates and look out for their well-being. 6. Keep your subordinates informed. 7. Build the team. 8. Employ your subordinates in accordance with their capabilities. 9. Know yourself and seek improvement. 10. Seek responsibility and accept responsibility for your actions. 11. Set the example.
see also: Wildland Fire Leadership Values

Wildland Fire Leadership Values
Three guiding values that should be the basis for the decisions that leaders make. The three values are: 1. Duty – How a leader values their job. Duty begins with everything required by law and policy, but is much more than that. A leader commits to excellence in all aspects of their professional responsibility so that when the job is done they can look back and say, “I couldn’t have given any more.” 2. Respect – How a leader values their co-workers. Respect for the individual forms the very basis for the rule of law in America. This value reminds leaders that those who follow are their greatest resource. Not all followers will succeed equally, but they all deserve respect. 3. Integrity – How a leader values himself or herself. An individual cannot be in charge of others unless they are in charge of their own actions. People of integrity separate what is right from what is wrong and act according to what they know is right, even at personal cost.
see also: Wildland Fire Leadership Principles

Wildland Fire Management Information (WFMI)
A Web site providing current weather and lightning data, as well as historic fire occurrence data. NWCG Unit Identifiers are also maintained on the site.

Wildland Fire Serious Accident
Any accident where one or more fatalities occur and/or three or more personnel are inpatient hospitalized as a direct result, or in support of wildland fire suppression or prescribed fire operations. Accident may result in substantial property or equipment damage of $250,000 or more.

Wildland Fire Situation Analysis (WFSA)
A decision-making process that evaluates alternative wildfire suppression strategies against selected environmental, social, political, and economic criteria, and provides a record of those decisions.

Wildland Fire Use
The application of the appropriate management response to naturally-ignited wildland fires to accomplish specific resource management objectives in pre-defined designated areas outlined in Fire Management Plans. Operational management is described in the Wildland Fire Implementation Plan (WFIP).
see also: Prescribed Fire
see also: Wildland Fire

Wildland Fire
Any non-structure fire that occurs in the wildland. Three distinct types of wildland fire have been defined and include wildfire, wildland fire use, and prescribed fire.
see also: Prescribed Fire
see also: Wildfire
see also: Wildland Fire Use

Wildland Urban Interface (WUI)
The line, area, or zone where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels.

Wildland
An area in which development is essentially non-existent, except for roads, railroads, powerlines, and similar transportation facilities. Structures, if any, are widely scattered.

Wind Direction
Compass direction from which wind is blowing.

Wind Profile
A chart of wind speed in relation to height, most commonly determined by a pilot balloon observation.

Wind Shear
A variation in wind speed and/or direction in a layer of the atmosphere or between layers. The variation may be in the horizontal or vertical dimensions and may result in significant turbulence depending upon the magnitude of the wind speed/direction differences. A strong wind shear may act like an inversion and inhibit plume rise. It may also fracture the smoke plume, not allowing smoke to rise much above terrain levels. A strong horizontal anticyclonic shear results in downward motion and may bring smoke aloft to the surface.

Wind Shift
(1) For aviation purposes, a change in the average wind direction of 45 degrees or more which takes place in less than 15 minutes if the wind speed during this period is 6 knots (3 m/s) or greater.
(2) For ground observation purposes, a change of at least 45 degrees in the direction of a significant wind, which occurs in a relatively short time frame.

Wind Speed
(1) Wind, in miles per hour, measured at 20 feet above open, level ground or as adjusted to meet this standard to compensate for height of ground cover, uneven ground, and nearby obstructions.
(2) (NFDRS) Wind, in mph, measured at 20 feet above ground, or above the average height of vegetation, and averaged over at least a 10-minute period. Also called wind velocity.

Wind Vectors
Wind directions used to calculate fire behavior.

Wind
The horizontal movement of air relative to the surface of the earth.

Wind-driven Wildland Fire
A wildland fire that is controlled by a strong consistent wind.

Windfall
Tree that has been uprooted or broken off by wind.

Windrow Burning
Burning slash that has been piled into long continuous rows. Also includes wildfire in vegetation planted to protect improvements or agriculture.

Winds Aloft
Generally, wind speeds and wind directions at various levels in the atmosphere above the domain of surface weather observations.

Windspeed Meter
A handheld device which indicates wind speed, usually in miles per hour.

Woody Fuel Moisture
In NFDRS, a calculated value representing the approximate moisture content of the live woody vegetation in the rating area expressed as a percentage of the oven dry weight of the sample.
see also: Herbaceous Fuel Moisture
see also: Measured Woody Fuel Moisture
see also: Woody Vegetation Condition

Woody Vegetation Condition
Part of the National Fire Danger Rating System (NFDRS). A code reflecting the moisture content of the foliage and small twigs [less than 1/4 inch (0.6 cm)] of living woody plants.
see also: Woody Fuel Moisture

Work Capacity Test (WCT)
A family of tests to determine firefighter physical capabilities. Work capacity tests are used to ensure that persons assigned to fire activities are physically capable of performing the duties of wildland firefighting and to meet National Wildfire Coordinating Group (NWCG) standards for wildland firefighters (Wildland Fire Qualification Subsystem Guide 310-1, NWCG, 1993). The WCT is a family of tests to determine firefighter physical capabilities at three levels: Arduous: “Duties involve field work requiring physical performance calling for above-average endurance and superior conditioning. These duties may include an occasional demand for extraordinarily strenuous activities in emergencies under adverse environmental conditions and over extended periods. Requirements include running, walking, climbing, jumping, twisting, bending, and lifting more than 50 pounds; the pace of work typically is set by the emergency condition.” Moderate: “Duties involve field work requiring complete control of all physical faculties and may include considerable walking over irregular ground, standing for long periods, lifting 25 to 50 pounds, climbing, bending, stooping, squatting, twisting, and reaching. Occasional demands may be required for moderately strenuous activities in emergencies over long periods. Individuals usually set their own work pace.” Light: “Duties mainly involve office-type work with occasional field activity characterized by light physical exertion requiring basic good health. Activities may include climbing stairs, standing, operating a vehicle, and long hours of work, as well as some bending, stooping, or light lifting. Individuals almost always can govern the extent and pace of their physical activity” Each performance level has its own unique Work Capacity Test: Pack Test: The pack test is a job-related test of the capacity for arduous work. It consists of a 3-mile hike with a 45-pound pack over level terrain. A time of 45 minutes, the passing score for the test, approximates an aerobic fitness score of 45, the established standard for wildland firefighters. Field Test: The field test is a job-related test of work capacity designed for those with moderately strenuous duties. It consists of a 2-mile hike with a 25-pound pack. A time of 30 minutes, the passing score, approximates an aerobic fitness score of 40. Walk Test: The walk test is designed to determine the ability to carry out light duties. It consists of a 1-mile test with no load that approximates an aerobic fitness score of 35. A time of 16 minutes, the passing score for the test, ensures the ability to meet emergencies and evacuate to a safety zone.

Work/Rest Ratio
An expression of the amount of rest that is required for each hour an individual is in work status. Current NWCG guidelines require one hour of rest for every two hours in work status.

Woven Jacket Fire Hose
Fire hose of conventional construction, woven on looms from fibers of cotton or synthetic fibers. Most fire department hose is double jacketed (i.e., it has an outer jacket protecting the inner one against wear and abrasion).

Wye
A hose connection with two outlets permitting two connections of the same coupling diameter to be taken from a single supply line.
see also: Reversible Siamese
see also: Siamese

— Z —

Zone Weather Forecast
A portion of the general fire weather forecast issued on a regular basis during the normal fire season specifically to fit the requirements of fire management needs; i.e., time, areas, and weather elements. These zones or areas are a combination of administrative and climatological areas, usually nearly the size of an individual forest or district.