Glossary of Fire Weather Terms


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Glossary of Fire Weather Terms

aerial coverageThe amount or percentage of fuels above the surface as viewed in a horizontal plane.
aerial fuelsAll live and dead vegetation above, but not contiguous with, the surface.
aspectThe direction a slope faces.
available fuelsFuels which will burn during the passage of a flaming front under specific environmental conditions.
combustionThe process by which fuels burn.
components of a fuel complexThese include the physical characteristics of the fuels (size, shape, and arrangement) as well as the dynamic characteristics (moisture content).
critical fire weather patternPatterns that can quickly increase fire danger and trigger rapid fire spread.
critical valuesThe threshold value of any weather or environmental parameter at which fires may ignite and/or spread rapidly.
crown firesFires which spread through the tops of trees or any other aerial fuels.
crowningWhen fires move rapidly from surface fuels to aerial fuels and then spread as crown fires.
curingThe natural seasonal drying process of annual and perennial vegetation (fuels).
dead fuel moistureThe amount of water in dead fuels.
dead fuelAny non-living organic matter that will burn.
dispatcherA person responsible for assigning (dispatching) personnel and/or equipment to a fire or other project.
dispersion descriptionA simple interpretative conversion from the numerical Dispersion Index
dispersion indexA numerical rating of how well smoke will disperse. Dispersion Table
duffA mat of partially decomposed organic matter immediately above the mineral soil, consisting of fallen foliage, live or dead herbaceous vegetation, and decaying wood.
extended forecastA forecast of weather conditions for a period extending beyond two days from the day of issue.
fine fuelSmall diameter (0-1/4 in or 0-0.64cm) fuels such as grass, leaves, pine needles, fern, tree moss, and some kinds of slash which, when dry, ignite readily and are consumed rapidly.
fire behavior analystThe member of an incident team that predicts fire behavior emphasizing the direction and rates of fire spread for fire suppression or control.
fire behaviorThe manner in which fuels ignite, flames develop, and fire spreads.
fire dangerA subjective expression of an objective assessment of environmental (fuels and weather) factors which influence whether fires will start and how they may spread.
fire environmentThe environmental conditions, influences, and modifying forces that determine the behavior of fires.
fire frequencyThe number of fires occurring in a given area over a given period of time.
fire growthThe increase in fire size (acres or hectares).
fire ignitionThe initiation of a fire.
fire intensityA measure of the heat intensity of the flaming zone of a fire front. Objectively expressed as BTU/square meter. Subjectively expressed in terms of fuel consumption, e.g., total, partial, etc.
fire linesFire control lines constructed by various mechanized equipment (e.g., heavy tractors, aerial retardant, etc.) or by crews with hand tools.
fire managerThe member of the incident team that oversees land management based on available resources, required protection, and the role of fire in that environment.
fire spreadThe movement of fire in all directions.
fire weather watchA watch issued when the forecaster feels reasonably confident that red flag conditions will develop in the next 12 to 48 hours.
firebrandsPieces of burning debris such as twigs, branches, logs or pine cones that may contribute to fire spread by rolling downhill or being carried aloft in the fire convection column.
flame lengthThe distance measured from the tip of the flame to the middle of the flaming zone at the surface.
foehnA strong downslope wind characterized by the effects of adiabatic (compressional) warming and drying.
forecast funnelThe methodology used in preparing a weather forecast by starting with large-scale features and working down in scale to smaller features to determine the weather that will affect a specific region.
fuel bed depthThe depth of the fuel bed including any duff and surface fuels.
fuel bedThe total volume of fuel in a given area.
fuel complexThe composite of the various combustible components of vegetation, live and dead, that occur on a site.
fuel loadingThe amount of organic material in a fuel complex measured in metric tons/hectare.
fuel moisture contentThe amount of water in a fuel, expressed as the percentage of its weight without moisture.
fuelAny organic matter on the ground or above the surface that will ignite and burn.
ground fuelsSee surface fuels.
haines indexA lower atmospheric stability and dryness index that can be one predictor of large fire growth due to plume-dominated fires.
headlineA brief statement at the beginning of a forecast that highlights dangerous or changing weather conditions.
ignition pointThe fuel temperature at which spontaneous combustion occurs.
ignitionThe initiation of combustion.
incident meteorologistA meteorologist trained and certified to provide on-site weather forecasting support to an incident management team at a fire or other incident.
key station forecastA forecast that takes into account an observing station location and the microscale effects on weather parameters in presenting exact values of weather parameters rather than ranges.
key stationA specific weather observing site in a zone.
lightning activity level (lal)An objective rating system used in the NFDRS that indicates the amount of cloud-to-ground lightning observed or forecast in a given area.
litterThe uppermost layer of loose debris composed of freshly fallen or slightly decomposed organic material such as dead twigs, branches, leaves, or pine needles.
live fuel moistureThe amount of water in live fuels.
live fuelAny live organic matter available to burn.
logging slashResidue (slash) from logging, such as limbs.
marine layerA shallow layer of air with relatively high humidity and cooler temperatures that moves from the ocean over land. It may be associated with diurnal land/sea breeze regimes or other features that increase on-shore pressure gradients.
mesoscaleA scale that ranges in size from a few kilometers to about 100 kilometers.
microscaleA scale that covers phenomena smaller than those in the mesoscale range.
miller-holzworth methodA method of determining mixing height and transport winds used to characterize smoke dispersal conditions.
model output statistics (mos)A generation of point specific output from a numerical model.
moisture factorThe ambient moisture (relative humidity) that effects fuels and the fire environment.
moisture of extinctionThe fuel moisture content at which combustion will not be sustained independently.
national fire danger rating system (nfdrs)A national system used by all land management agencies to assess fuels, weather, and fire potential on a daily basis during fire season.
national fire danger rating system modelA group of 20 models that represents various types of fuels.
oven dry weightThe resultant weight of a fuel sample after all moisture has been driven off by oven drying.
peatPartly decayed, moisture-absorbing plant matter used as a plant covering or fuel.
plume-dominated firesFires with well-developed convection columns whose spread is normally characterized by pulsing, usually in all directions.
prescribed fire/burnA natural or human-ignited fire burning under a strict set of predetermined conditions to fulfill specified land management objectives.
probability of ignitionA rating describing the probability that a firebrand that lands on a fuel will cause a fire.
red flag criteriaA locally determined set of criteria that expresses environmental and meteorological conditions that would provide for fire starts and rapid, dangerous fire spread.
red flag warningA warning issued by fire weather forecasters when red flag criteria are met or expected to be met within 12-24 hours. The warning highlights weather of particular importance to fire behavior and potentially extreme burning conditions or many new fires. It is also used to alert customers to changes in weather that increase the fire danger. Red flag warnings should always be coordinated with the customer.
short-range forecastA weather forecast made for a time period generally not greater than 48 hours in advance.
slashDebris left after logging, pruning, thinning, or brush cutting; also debris resulting from thinnings, wind, or fire. It may include logs, chunks, bark, branches, stumps, and small, broken trees or brush.
slopeThe percent of incline or steepness.
smoke management parametersThe weather parameters used to forecast smoke dispersal.
spot weather forecastA forecast tailored for a specific fire. These forecasts are issued on an as-needed basis and are requested by a customer.
spottingThe process of fire spread by sparks, embers, or firebrand that are carried by the wind beyond an on-going fire.
stability factorThis is determined by temperature differences between two atmospheric layers.
suppressionThe act and techniques of putting fires out.
surface fuelsAll combustible material on surface, including any duff layers or piled slash.
synopsisA statement giving a brief general review or summary.
thermal beltsAn area along the middle of a mountain slope that typically experiences the least diurnal variation in temperature and humidity, thus has the highest daily average temperatures, and the lowest average relative humidity.
timber litterMixed litter, leaves, needles, branches, twigs, or bark fallen from trees.
timelagAn indication of the rate a dead fuel gains or loses moisture due to changes in its environment.
topographyA detailed description of surface features including rives, lakes, etc.
transport windsWinds in the lower mixed layer, used for smoke dispersal forecasts.
urban-wildland interfaceThe region where urban development encroaches on wildlands.
ventilation indexThis is the product of the mixing height and transport wind speed, and is an indicator of dispersion potential.
wetting rainA rain event that produces enough rain to sufficiently wet fuels so that ignition or sustained combustion is unlikely.
wind-driven firesFires that spread primarily as a result of winds. These fires typically have elongated elliptical patterns, burn actively due to increased oxygen supply, and have long flame lengths with proportionally short flame heights that cause rapid heating of fuels ahead of the flaming front.
zone weather forecastA 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. These zones or areas are a combination of administrative and climatological areas, usually nearly the size of an individual forest or district.
« Last Edit: 03 Aug, 2021, 19:38:27 by spiros »


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