General Information

on the

Fire Weather System

Of

Georgia Forestry Commission

 

 

Weather Forecast

Georgia Forestry Commission's (GFC) fire weather system is an enhanced version of the forecast segment of the Forestry Weather Interpretation System (FWIS) developed at the Southern Forest Fire Laboratory in cooperation with the southern forestry community in the late 70’s and early 80’s (Paul 1981, Paul and Clayton 1978).  When the pilot test of FWIS was completed, GFC adapted parts of the system for their use.  Adaptations included an expansion of the forecast variables, and a sophisticated automation process.  The automation process is especially important because the system will run automatically even if there is no staff meteorologist to monitor the operation.  During normal working hours (8am-430pm Monday through Friday), staff meteorologist may intervene and make manual changes to the forecast as required.  The automation process sets limits such that a “small” forecast error may occur, but a “large” error is unlikely.  Whenever fire danger is high, or other critical weather driven forestry events are occurring, staff meteorologist may work after hours, weekends or holidays.

 

3-day 5-period forecasts are generated twice per day (5:30am and 12:30pm EST) for each district or district component.  7-day forecasts are generated in the morning only.  Most districts are not split, but some are split into North-South, or coastal-inland components.  Districts that are climatologically similar may be combined for forecast purposes, if combining is operationally acceptable.  The forecast is for a geographic area, and consequently variables such as temperature, relative humidity and wind are specified as a range of values most likely to occur over the district. 

 

In addition to the text weather forecasts, maps and graphs of selected observed or forecast weather and fire related variables are produced. Current and forecast fire danger rating information for GFC and co-operators weather station network are generated.  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 are available as well.  All the products can be accessed through GFC's Fire Weather Homepage (http://weather.gfc.state.ga.us).

 

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:

  1. Fire danger rating relates only to the potential of the initiating fire.
  2. The ratings are relative, not absolute.  Relationships are linear except in use of burning index.
  3. Fire danger is rated from a worst case approach
  4. Fire danger is rated for a broad fuel model.

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 1:00pm EST.  Then, fire danger indices will be computed.  Weather stations can be called at any time when data are needed to support forestry operations.

 

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 University of Georgia, are collected as well.

 

 


Figure 1 Location of GFC and Co-operators (excluding UGA) fire danger weather stations.

 

 

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 1.  Name, location, elevation, and NFDRS fuel model used for the weather stations accessed by the GFC (excluding UGA stations)

Station Name

County

Latitude

Longitude

Elevation

Fuel Model

WIMS ID

NESDIS ID

Adel

Cook

31.1097

-83.4269

154

D

98401

3100E40E

Americus

Sumter

32.1106

-84.1841

400

C

95501

3100929E

Watkinsville

Oconee

33.8887

-83.4191

675

C

92702

31003266

Baxley

Appling

31.7136

-82.4211

109

D

97701

3100D194

Brender

Jones

33.0506

-83.7164

280

C

94301

3100621A

Byromville

Dooly

32.1681

-83.9747

242

C

95701

310123EA

Camilla

Grady

31.2141

-84.2362

62

C

98201

31010506

Chatsworth

Murray

34.7664

-84.7589

748

E

90401

310007FC

Claxton (DoD)

Evans

32.1000

-81.9000

250

D

 

 

Cumberland Island (NPS)

Camden

30.7700

-81.6000

25

D

 

 

Dallas

Paulding

33.8334

-84.7400

907

E

92201

31002110

Dawsonville

Dawson

34.3762

-84.0599

1213

C

91101

3100148A

Eddy Tower (USFS)

FL

30.5100

-82.3300

187

D

 

 

Fargo (FWS)

Clinch

30.7800

-82.3400

125

D

 

 

Folkston (FWS)

Charlton

30.7500

-82.1000

125

D

 

 

Fort Benning

Chattahoochee

32.3822

-84.8678

460

C

 

 

Louisville

Jefferson

32.9860

-82.3822

195

C

94501

3100716C

Milledgeville

Baldwin

32.0103

-83.2073

254

C

93601

310081E8

McRae

Wheeler

32.0964

-82.8841

510

C

96201

3100A704

Metter

Candler

32.3913

-82.0373

99

C

96301

3100B472

Midway

Liberty

31.7842

-81.4386

1

D

96801

3100C2E2

Newnan

Coweta

33.3654

-84.7500

775

C

92901

310044F6

Richmond Hill (DoD)

Bryan

31.9600

-81.3300

27

D

 

 

Savannah (FWS)

Chatham

32.1700

-81.1200

120

D

 

 

Sterling

Glynn

31.2570

-81.6107

1

D

98801

3100F778

Sumter (USFS)

SC

34.8500

-83.3000

1600

R

 

 

Taylor Creek

Liberty

31.9417

-81.7528

86

D

 

 

Washington

Wilkes

33.7807

-82.8161

593

C

93501

31005780

Waycross

Ware

31.2466

-82.4014

37

D

99701

31011670

Notes:

     The stations are owned by the GFC unless the station name is followed by an abbreviation in

      parenthesis i.e. (USFS).  The abbreviations are noted below.

           DoD    - Department of Defense

           FWS     - U.S. Fish and Wildlife Service 

           NPS      - U.S Department of Interior, Park Service

           USFS  - U.S. Department of Agriculture, Forest Service

 

      All Locations are North latitude and West(-) longitude.


 

Table 2: Class Day determination points

Station/

Fuel Model

Class 1

Class 2

Class 3-

Class 3

Class 3+

Class 4

Class5

Determination Points

Valid Time

Determination Points

Based on

Description

Low

Moderate

Moderate to High

High

High to Very High

Very High

Extreme

------

 

BI Percentiles

0th to 20th

21st to 45th

46th to 60th

61st to 80th

81st to 90th

90th to 97th

97th to 100th

------

 

Chatsworth

0

17

25

28

33

39

44

2013- 

2010-2012

Dallas

0

12

19

21

24

27

31

2013- 

2010-2012

Dawsonville

0

1

10

12

15

17

20

2013- 

2010-2012

Watkinsville

0

6

11

13

16

19

23

2013- 

2010-2012

Washington

0

6

11

13

16

19

22

2013- 

2010-2012

Louisville

0

8

13

15

18

20

24

2013- 

2010-2012

Newnan

0

2

10

12

16

18

22

2013- 

2010-2012

Milledgeville

0

7

12

14

17

20

23

2013- 

2010-2012

Brender

0

5

9

11

13

15

17

2013- 

2010-2012

McRae

0

8

13

15

18

21

24

2013- 

2010-2012

Americus

0

8

14

16

19

23

28

2013- 

2010-2012

Byromville

0

8

13

15

19

22

26

2013- 

2010-2012

Camilla

0

9

13

15

19

21

25

2013- 

2010-2012

Metter

0

8

12

14

17

19

23

2013- 

2010-2012

Baxley

0

48

71

79

93

102

114

2013- 

2010-2012

Waycross

0

46

69

79

93

104

117

2013- 

2010-2012

Brunswick

0

33

57

65

76

83

93

2013- 

2010-2012

Adel

0

44

67

76

88

97

110

2013- 

2010-2012

Midway

0

38

57

64

73

79

88

2013- 

2010-2012

Sumter NF, SC

0

5

15

18

21

23

27

2013- 

2010-2012

Taylor Creek

0

38

61

68

79

86

101

2013- 

2010-2012

Folkston

0

43

66

76

90

98

112

2013- 

2010-2012

Fargo

0

39

66

73

86

95

108

2013- 

2010-2012

Claxton

0

41

64

72

83

92

106

2013- 

2010-2012

Richmond Hill

0

40

62

69

78

85

96

2013- 

2010-2012

Lawson

0

39

55

63

73

83

97

2013- 

2010-2012

Fort Benning

0

9

13

15

18

20

24

2013- 

2010-2012

Note: The listed values are the minimum value for each Class day.  For example, when Watkinsville has BI of 19-22, it has Class 4 Day. 

 

 

 

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.  Ogden, UT: US Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station; 1977. 63pp..

 

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 California mixed chaparral generally 30 years or older. The F model is more appropriate for pure chamise stands. The B model may also be used for the New Jersey pine barrens.

 

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 Arizona, Utah, and Colorado. It also applies to young, closed stands and mature, open stands of California mixed chaparral. Open stands of pinyon-juniper are represented; however, fire activity will be overrated at low windspeeds and where there is sparse ground fuels.

 

 

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 Florida. It may be useful in other marsh situations where the fuel is coarse and reedlike. This model assumes that one-third of the aerial portion of the plants is dead fast-spreading, intense fires can occur even over standing water.

 

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 Virginia, North and South Carolina coasts are the ideal of Fuel Model O.  If the plants do not meet the 6-foot criteria in those areas, Fuel Model D should be used.

 

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 Great Basin and the Intermountain West are characteristic of T fuels. The shrubs burn easily and are not dense enough to shade out grass and other herbaceous plants. The shrubs must occupy at least one-third of the site or the A or L fuel models should be used. Fuel Model T might be used for immature scrub oak and desert shrub associations in the West, and the scrub oak-wire grass type in the Southeast.

 

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.