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General Information on the Fire Weather System Of Georgia Forestry Commission Weather Forecast Georgia Forestry Commission's (GFC)
used National Weather Service’s (NWS)
Fire Weather Dashboard to get to weather products produced by the
NWS. GFC produces observed or forecast
weather maps/graphs. GFC also
generates current and forecast fire danger rating information for GFC and
co-operators weather station network. Other
products available through GFC's Fire Weather Homepage (https://weather.gfc.state.ga.us)
include Current weather at National Weather Service's (NWS) weather stations
in Georgia, historical data from the GFC weather stations, and a climate
outlook from NWS's Climate Prediction Center. NFDRS NFDRS stands for National Fire Danger
Rating Systems. The current version of
the National Fire Danger Rating System was developed by the US Forest Service
(Burgan, 1988) for predicting fire occurrence and behavior based on fuels,
topography, man‑caused fire risk factors and current weather
conditions. Although the National Fire Danger Rating System indices should
not be directly applied to any particular site, they do supply the
practitioner with a set of indices that can be used to compare recent
history, and adjacent fire management areas.
Thus, it is very important to understand the principles of fire danger
rating:
Experienced practitioners can translate
these general area based indices to probable fire behavior at specific burn
site. Detailed explanation of the fire
danger indices can be found by clicking "Explanation of NFDRS
Indices" on the fire weather homepage. Weather data are input into NFDRS and a
number of indices are produced. These
fire danger indices are used to support prescribed burning activities and
wildfire control operations. Weather
data are collected automatically daily at Weather Station Network GFC operates a network of 19 automated weather stations
throughout the state (Figure 1). The
stations record current weather conditions each hour. Weather data from stations maintained by
cooperating agencies, including US Forest Service, US Park Service,
Department of Defense and
GFC currently uses NFDRS fuel models C, D, and E. Definitions of the various fuel models are
included in (Appendix A). Location
and fuel model associated with each station is shown in Table 1. The Georgia Forestry Commission uses
Burning Index (BI) to determine Class Day.
The determination points are station specific based on BI percentile
distribution at the station. The BI
determination points for all the stations are listed in Table 2. Table 3 shows the Energy Release Component
(ERC) percentile points for all stations.
Table 1. Name, location, elevation, and NFDRS fuel
model used for the weather stations accessed by the GFC (excluding UGA
stations)
Notes: The abbreviations are noted below. GFC - Georgia Forestry Commission DoD - Department of Defense FWS - NPS -
U.S Department of Interior, Park Service USFS - All Locations are North latitude and
West(-) longitude. Table 2: Class Day determination points
Note: The
listed values are the minimum value for each Class day. For example, when Americus has BI of 22-24,
it has Class 4 Day. Table 3: Energy Release Component (ERC)
Percentiles
Note: The
listed values are the minimum value for each Percentile range. For example, when Americus has ERC of
22-25, it between 90th and 97th percentile. REFERENCES Deeming, John E.; Burgan, Robert E.; Cohen, Jack D. The National
Fire-Danger Rating System – 1978. 1988 Revisions to the 1978 National
Fire-Danger Rating System. General
Technical Report INT-39. Paul, J.T.,
and J. Clayton. User manual: Forestry Weather Interpretation System (FWIS). Asheville, NC: U.S. Department of
Agriculture, Forest Service, Southeastern Forest Experiment Station and
Atlanta, GA: Southeastern Area State
and Private Forestry, in cooperation
with the U.S. National Weather Service, NOAA, Silver Spring, M;. 1978. 83pp. APPENDIX A FUEL
MODEL DEFINITIONS Definitions
extracted from (Deeming, et al. 1977). FUEL MODEL A This fuel model represents
western grasslands vegetated by annual grasses and forbs. Brush or trees may
be present but are very sparse, occupying less than one third of the area.
Examples of types where Fuel Model A should be used are cheatgrass and medusahead. Open pinyon-juniper, sagebrush-grass, and
desert shrub associations may appropriately be assigned this fuel model if
the woody plants meet the density criteria. The quantity and continuity of
the ground fuels vary greatly with rainfall from year to year. FUEL MODEL B Mature, dense fields of
brush 6 feet or more in height are represented by this fuel model. One-fourth
or more of the aerial fuel in such stands is dead. Foliage burns readily.
Model B fuels are potentially very dangerous, fostering intense,
fast-spreading fires. This model is for FUEL MODEL C Open pine stands typify
Model C fuels. Perennial grasses and forbs are the primary ground fuel but
there is enough needle litter and branchwood
present to contribute significantly to the fuel loading. Some brush and
shrubs may be present but they are of little consequence. Situations covered
by Fuel Model C are open, longleaf, slash,ponderosa,Jeffrey,
and sugar pine stands. Some pinyon-juniper stands may qualify. FUEL MODEL D This fuel model is
specifically for the palmetto-gallberry
understory-pine overstory association of the southeast coastal plains. It can
also be used for the so-called "low pocosins" where Fuel Model 0
might be too severe. This model should only be used in the Southeast because
of a high moisture of extinction. FUEL MODEL E Use this model after leaf
fall for hardwood and mixed hardwood-conifer types where the hardwoods
dominate. The fuel is primarily hardwood leaf litter. The oakhickory
types are best represented by Fuel Model E, but E is an acceptable choice for
northern hardwoods and mixed forests of the Southeast. In high winds, the
fire danger may be underrated because rolling and blowing leaves are not
accounted for. In the summer after the trees have leafed out, Fuel Model E
should be replaced by Fuel Model R FUEL MODEL F Fuel Model F is the only
one of the 1972 NFDRS Fuel Models whose application has changed. Model F now
represents mature closed chamise stands and oakbrush
fields of FUEL MODEL G Fuel Model G is used for
dense conifer stands where there is a heavy accumulation of litter and downed
woody material. Such stands are typically overmature and may also be
suffering insect, disease, wind, or ice damage-natural events that create a
very heavy buildup of dead material on the forest floor. The duff and litter
are deep and much of the woody material is more than 3 inches in diameter.
The undergrowth is variable but shrubs are usually restricted to openings.
Types meant to be represented by Fuel Model G are hemlock-Sitka spruce, Coast
Douglas-fir, and windthrown or bug-killed stands of lodgepole pine and
spruce. FUEL MODEL H The short-needled conifers
(white pines, spruces, larches, and firs) are represented by Fuel Model H. In
contrast to Model G fuels, Fuel Model H describes a healthy stand with sparse
undergrowth and a thin layer of ground fuels. Fires in H fuels are typically
slow spreading and are dangerous only in scattered areas where the downed
goody material is concentrated. FUEL MODEL I Fuel Model I was designed
for clearcut conifer slash where the total loading of materials less than 6
inches in diameter exceeds 25 tons/acre. After settling and the fines
(needles and twigs) fall from the branches, Fuel Model I will overrate the
fire Potential. For lighter loadings of clearcut conifer slash, use Fuel
Model J, and for light thinnings and partial cuts
where the slash is scattered under a residual overstory, use Fuel Model K. FUEL MODEL J This model complements Fuel
Model I. It is for clearcuts and heavily thinned conifer stands where the
total loading of materials less than 6 inches in diameter is less than 25
tons/acre. Again, as the slash ages, the fire potential will be overrated FUEL MODEL K Slash fuels from light- thinnings and partial cuts in conifer stands are
represented by Fuel Model K. Typically the slash is scattered about under an
open overstory. This model applies to hardwood slash and to southern pine
clearcuts where the loading of all Fuels is less than 15 tons/acre. FUEL MODEL L This fuel model is meant to
represent western grasslands vegetated by perennial grasses. The principal
species are coarser and the loadings heavier than those in Model A fuels.
Otherwise the situations are very similar; shrubs and trees occupy less than one-third
of the area. The quantity of fuel in these areas is more stable from year to
year. In sagebrush areas Fuel Model T may be more appropriate. FUEL MODEL N This fuel model was
constructed specifically for the sawgrass prairies of south FUEL MODEL O The O fuel model applies to
dense, brushlike fuels of the Southeast. O fuels,
except for a deep litter layer, are almost entirely living in contrast to B
fuels. The foliage burns readily except during the active growing season. The
plants are typically over 6 feet tall and are often found under an open stand
of pine. The high pocosins of the FUEL MODEL P Closed, thrifty stands of
long-needled southern pines are characteristic of P fuel: A 2- to 4-inch
layer of lightly compacted needle litter is the primary fuel. Some small
diameter branchwood is present but the density of
the canopy precludes more than a scattering of shrubs and grass. Fuel Model P has the high moisture of
extinction characteristic of the Southeast. The corresponding model for other
long-needled pines is U. FUEL MODEL Q Upland Alaskan black spruce
is represented by Fuel Model Q. The stands are dense but have frequent
openings filled with usually inflammable shrub species. The forest floor is a
deep layer of moss and lichens, but there is some needle litter and small-diameter
branchwood. The branches are persistent on the
trees, and ground fires easily reach into the tree crowns. This fuel model
may be useful for jack pine stands in the Lake States. Ground fires are
typically slow spreading, but a dangerous crowning potential exists. Users
should be alert to such events and note those levels of Spread Component (SC)
and BI when crowning occurs. FUEL MODEL R This fuel model represents
the hardwood areas after the canopies leaf out in the spring. It is provided
as the off-season substitute for E. It should be used during the summer in
all hardwood and mixed conifer-hardwood stands where more than half of the overstory
is deciduous. FUEL MODEL S Alaskan or alpine tundra on
relatively well-drained sites is the S fuel. Grass and low shrubs are often
present, but the principal fuel is a deep layer of lichens and moss. Fires in
these fuels are not fast spreading or intense, but are difficult to
extinguish. FUEL MODEL T The bothersome
sagebrush-grass types of the FUEL MODEL U Closed
stands of western long-needled pines are covered by this model. The ground
fuels are primarily litter and small branchwood.
Grass and shrubs are precluded by the dense canopy but occur in the
occasional natural opening. Fuel Model U should be used for ponderosa,
Jeffrey, sugar pine, and red pine stands of the Lake States. Fuel Model P is
the corresponding model for southern pine plantations. |
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