United States
Department of
Agriculture
Forest Service
Pacific Southwest
Forest and Range
Experiment Station
General Technical
Report PSW-77
Potential Fire Behavior
in California: an atlas and guide
for forest and brushland managers
Bill C. Ryan
The Author:
BILL C. RYAN, a research meteorologist, is assigned to the Station's forest meteorol­
ogy research unit, headquartered at the Forest Fire Laboratory, Riverside, Calif. He
earned a bachelor's degree in chemistry at the University of Nevada (1950), a master's
in meteorology at Texas Agricultural and Mechanical University (1964), and a doc­
torate in climatology at the University of California, Riverside (1974). He joined the
Station staff in 1967.
Publisher:
Pacific Southwest Forest and Range Experiment Station
P.O. Box 245, Berkeley, California 94701
July 1984
Potential Fire Behavior
in California: an atlas and guide
for forest and brushland managers
Bill C. Ryan
CONTENTS
Introduction .......................................................................................... 1 The Atlas ............................................................................................... 1 Application ......................................................................................... 1
Derivation ........................................................................................... 2
Interpreting the Data ........................................................................... 2
Persistence of Potential Fire Characteristics ........................................ 2 Frequency Distribution ....................................................................... 3
Minimum and Maximum Temperatures and Relative Humidities ....... 3
Precipitation ........................................................................................ 3
Windspeed and Direction .................................................................... 3
Appendix A --Figures 2 to 10 ............................................................... 4 Appendix B--Figure 11, Tables 1 to 18 ................................................ 9 References ........................................................................................... 15
K
nowledge of potential fire-behavior characteristics is
needed by forest and brushland managers. They need
to know the most probable dates or periods of dangerous
fire conditions and probable fire intensities and spread
rates. For prescribed fires, they need to know probable
dates and lengths of time the burns can be continued within
prescription limits. They need to know when weather and
fuel conditions will allow accumulated debris and fuel to
burn, but not burn so intensely that desirable vegetation is
killed or the fire becomes wild. They also need information
to estimate whether or not the wind will take smoke into
populated areas and cause problems.
At the National Fire Weather Data Library, Fort Col­
lins, Colorado, the Forest Service, U.S. Department of
Agriculture, maintains on magnetic tapes a mass of data on
weather and fuel moisture. These data are collected from
fire-danger rating stations throughout the United States
(Furman and Brink 1975). With these data and techniques
developed by Deeming and others (1977) potential fire
characteristics can be estimated.
This report describes an Atlas that provides statistical
analyses of potential fire behavior in California's wildlands. Charts and information from the fire-danger rating
station at Mount Hebron in northern California serve as an
example of the information provided by the Atlas.
THE ATLAS
•
Determining probable length of time that weather
and fuel variables will remain within prescription
limits and burns can be continued.
• Estimating potential fire characteristics between ob­
servations at danger-rating stations.
• Determining dates or periods when prescription
conditions will probably occur.
• Providing data to facilitate estimating number of
acres that can be burned within prescription each
month.
Fire suppression:
• Estimating probable number of days in, above, or
below specific ranges of fire intensity or spread
rates.
• Estimating probable maximum fire intensities and
spread rates.
• Estimating probability of fire intensities or spread
rates within specific ranges.
• Estimating most probable dates or periods of dan­
gerous fire conditions.
General purposes:
• Estimating probability of occurrence of specific
weather conditions and fuel moisture.
• Estimating probability of specific ranges of windspeed and direction during a given month.
Because the information in the Atlas is based on the
National Fire-Danger Rating System--1978 (NFDRS),
the four basic principles of the System should be con­
sidered when using the Atlas:
"1. The NFDRS relates only to the potential of the
initiating fire. An initiating fire is one that does not behave
erratically; it spreads without spotting through continuous
The Atlas includes 10 volumes. Volume 1 lists the contents and describes the data used to derive the statistics and
information in the Atlas. The other nine volumes include
one volume for each of the nine sections of California
(fig. 1).
Maps of each section (appendix A:figs. 2 to 10; appendix B: tables I to 18) show locations of observation stations
whose fire weather statistics are included in the Atlas. The
maps are accompanied by a list of the stations in each
section showing each station name, number, number of
years of observation, and the total number of observa­
tions. Stations on the maps are identified by the last four
digits of the station number. Because some areas overlap
two sections, some station locations are plotted in two
sections. When that occurs, information and statistics for
that station are included in only one section. The section is
indicated by a number next to the station number.
Application
The information contained in the Atlas can help manag­
ers in ...
Prescribed burning:
• Estimating the probable number of days available
with spread component (SC), burning index (BI), and igni­
tion component (IC) within prescription limits.
Figure 1--Areas of California are outlined into nine sections. Each
section contains fire-danger observation stations, as indicated on
maps (appendix A: figs. 2-10).
ground fuels. Crowning and spotting are not now addressed.
However, experience with the NFDRS will enable users to
identify the critical levels of fire danger when such behavior
is highly probable.
"2. The System only addresses those aspects of fire con­
trol strategy affected by fire occurrence and behavior. The
concept of containment, as opposed to extinguishment, is
basic because it allows us to limit the scope of the rating
problem to the behavior potential of the headfire. Other
aspects of the containment job such as accessibility, soil
condition, and resistance to line construction must be eval­
uated by other means.
"3. The ratings are relative, not absolute. Wherever pos­
sible, we have structured the component or index so that it
is linearly related to the particular aspect of the fire prob­
lem being rated. Thus, when the value of a component or
index doubles, the fire manager should expect a doubling
of the rated activity relative to what has been recently
observed. The BI is an exception that will be addressed
later.
"4. Fire danger is rated from a worst case approach. Fire
weather is measured at the time of day when fire danger is
normally the highest; and, wherever possible, in the open at
midslope on southerly or westerly exposures. This impor­
tant principle must be understood if fire-danger ratings are
to be properly interpreted."
Derivation
To develop the Atlas, data from the National Fire
Weather Data Library were used. Data were processed
from magnetic tapes with FORTRAN code modified from
the National Fire-Danger Rating System's (Deeming and
others 1977) FIREDAT routine (Main and others 1982).
Necessary variables such as 1-hour timelag fuel moisture
(TLFM), 10-hour TLFM (if necessary), 100-hour TLFM,
1000-hour TLFM, herbaceous and woody fuel moisture,
spread component, burning index, and ignition compo­
nent were computed.
Spread component, BI, and IC were calculated with
current (summer 1981) fuel models, slope, and herbaceous
types, as recorded on the 10-day Fire Danger and Fire
Weather Record for the stations. The date of greenup-­
when the spring flush of growth becomes generally
apparent--is needed for calculations of live fuel moisture.
The dates stored in the Administrative Forest Fire Infor­
mation Retrieval and Management System (AFFIRMS)-­
for 1981 and 1982 were used. When the greenup date was
not cataloged in AFFIRMS, dates were obtained from the
agency responsible for the observations or were estimated
on the basis of elevation and dates given for surrounding
stations. The potential fire characteristics in or near the
month in which greenup begins may vary greatly. If greenup during a particular year is earlier than the date used to
produce the tables, fuel moisture will tend to be greater and
fire severity potential will tend to be less between the two
2
dates. If greenup is later, fuel moisture will tend to be less
and fire severity potential greater.
Information about each observation station's fuel mod­
els, location, elevation, length of record, agency affiliation
and protection unit are given. The information for Mount
Hebron Ranger Station (fig. 11) is included as an example,
along with statistics of weather and potential fire character­
istics (tables 1-18). Inventories of observations each year of
record for fire-danger observation stations can also be
obtained from the National Fire Weather Data Library
(Furman and Brink 1975).
INTERPRETING THE DATA
Fire weather observations, except for minimum and
maximum temperatures and relative humidities, are
recorded for 1300 P.s.t. only. Statistics derived from
observations taken at one time of the day cannot be
assumed to be representative of conditions at other times of
the day. This fact must be considered when using the
statistics.
Length of record of observations taken at a location is
significant because the longer the record, the more confi­
dence that can be placed in the statistics of that record. In
California, records vary from only a few months to more
than 20 years. The confidence that can be placed in the
statistics, therefore, varies greatly from station to station.
In the Atlas, statistics were computed for only those sta­
tions with at least 4 years of data for 1 or more months of
the year after 1972. The number of observations and years
of record have been included with the other statistics to
help users evaluate the reliability of the information and
establish confidence levels. For example, in April 1973
through December 1981, at Mount Hebron Ranger Sta­
tion, the SC, BI, and IC indicated potentially severe fire
conditions compared with other months (tables 2, 4, 6).
Only 11 observations were recorded in April during the
9-year period, however. Therefore, these statistics are not
reliable indicators of potential fire conditions to be ex­
pected in April.
Persistence of Potential Fire
Characteristics
The persistence of the spread component was analyzed
by dividing its range into 10 intervals (table 1). Class inter­
vals were chosen subjectively on the basis of ranges of
spread rates for different fuels. The number of consecutive
days from the initial day (0) to runs of nine (9) days, was
calculated. The percentages of time, according to records,
that the SC calculated on day 0 lasted 1, 2, 3, and up to 9
days, were tabulated. The number 29 (circled in table 1)
indicates that 29 percent of the time during periods of
record when an SC of between 6 and 10 occurred, it
remained 6 or more for 4 days. The number of occurrences
of SC in each class is in the column labeled "Obs." (for
observations). For example, the number of occurrences of
SC between 6 and 10 during the period of record was 673.
(The SC is scaled so that it is numerically equal to the
theoretical rate of spread in feet per minute.)
The persistence of the BI (table 3) and IC (table 5) were
also determined; these tables are similar to table 1. Class
intervals for BI were based on the adjective classes used by
the Pacific Southwest Region and the California Depart­
ment of Forestry. Those for IC were obtained by dividing
the range (0-100) into 10 equal parts.
Persistence of SC, BI, and IC was considered broken if a
3-day or greater break in sequence of observations oc­
curred; that is, if 3 or more days in a row of observations
were missing, persistence of all classes (except the lower
class) was considered broken. Calculations were made only
after 1972 because records of minimum and maximum
temperatures and relative humidities were not available for
earlier years.
Frequency Distribution
Spread component, BI, IC, fuel moisture variables, and
weather variables were divided into 10 classes each. An
empirical distribution (survival) function
Fm (x) =
N({x i : x i ≥ X})
•100
n
was calculated for each of the 10 lower class boundaries X
for each month in which
N({xi: xi≥X})
is the number of observed values xi that are greater than or
equal to X, and n is the total number of observations for
the month. The function was computed to give the frequency
of occurrence for each variable for each month in tables 2,
4, 6, 7, 9, and 11 through 16. The total number of observa­
tions for each class, for each month and for the total
periods of record are given for each variable.
Class intervals for SC were chosen subjectively on the
basis of ranges of spread rates for different fuels. Class
intervals for BI were determined on the basis of the adjec­
tive classes used by the Pacific Southwest Region and the
California Department of Forestry. The class intervals for
the other variables were obtained by dividing the estimated
maximum ranges of the variables into 10 equal parts.
Table 7 gives the empirical distribution function as
defined above for temperature for each month. The
number circled in table 7, for example, indicates that
74 percent of the time in June the temperature at 1300 P.s.t.
reaches at least 65° F (18.3° C). The percentage of tempera­
ture in each specific class can be found by subtracting the
percentage on the line below. For example, the percentage
of days with temperatures at 1300 P.s.t. from 65° F
(18.3° C) to 77° F (25° C) in June is 43 (74 percent minus
31 percent). The number of days with temperature from
65° F (18.3° C) to 77° F (25° C) in June is 263 (43 percent of
612)-an average of about 12 1/2 days each June, for the
21-year period.
Maximum and minimum magnitudes and number of
observations for each variable for the months of record are
also included in the tables.
Statistics of 100-hour TLFM, 1000-hour TLFM,
herbaceous-fuel moisture, and woody-fuel moisture content were calculated only for the years after 1972, when
records of maximum and minimum temperatures and rela­
tive humidities were generally available.
Minimum and Maximum Temperatures
and Relative Humidities
Records of maximum and minimum temperatures and
relative humidities were not taken until 1973 at fire weather
stations. Thus, tables 8 and 10 are based on data taken after
1972. The record highs, record lows, mean maximums,
mean minimums, and means for each month are given in
degrees Fahrenheit.
Precipitation
Precipitation amounts and means in inches are given for
all months and years of record when possible (table 17).
Often, records for months or years are incomplete, so
monthly or annual precipitation cannot be determined.
For example, no complete year's record was made for Mt.
Hebron Ranger Station.
Windspeed and Direction
The percent of joint occurrences of windspeeds and
directions for each month were computed (for example,
table 18). Windspeeds are divided into 10 classes as shown
on the left side of the table. Directions are given to eight
points of the compass (eight direction classes). The tables
list the percent of joint occurrences of windspeeds in 3 mi/ h
(1.3 m/s) classes, and directions in eight points of the
compass. For example, in table 18, the circled number 2
indicates that in the 21-year period in the month of May, SE
winds from 10 to 12 mi/h (4.5 to 5.4 m/s) occurred 2
percent of the time at 1300 P.s.t. at Mt. Hebron Ranger
Station.
Because of their similarity to other tables, several tables
included in the Atlas for Mount Hebron are not included
here. They are the tables that show joint occurrences of
windspeed and direction for Mount Hebron for other
months of record, June-November, and tables of SC, BI,
and IC for fuel model T, which are similar to tables 1-6 in
this report for fuel model G.
3
APPENDIX A-Figures 2 to 10
Figures 2 through 10 each contain a map of a section of
California. Each map is accompanied by a list of the sta­
tions in the section showing station name and number,
number of years of observations, and total number of
observations. Stations on the maps are identified by the
last four digits of the station number. Because some areas
overlap two sections, some station locations are plotted in
two sections. A number (superscript) after a station
number indicates the section in which information and
statistics are given for that station. The following abbrevia­
tions are used in the lists of stations:
BRKRDG
FFS
FS
GS
HQ
LAVBDS
LO
MLKRCH
RD
RS
SAWMPK
WBO
WHSHQD
Stations in Section 1:
Station
Figure 2--Section 1. 4
4
Black Fox Mountain LO
Lodge Pole GS
McCloud RS
Mt. Hebron RS
Mt. Shasta WBO
Orr Mountain LO
Round Mountain LO
Tennant GS
LAVBDS
Adin RS
Blue Mountain LO
Canby RS
Sugar Hill LO
Timber Mountain LO
Cedarville
Big Bend GS
Fall River Mills RS
Hat Creek Rim LO
Hirz Mountain LO
Lakeshore GS
Manzanita Lake
Redding
Squaw Creek GS
Sims
Bieber FFS
Blacks Ridge LO
Bogard RS
Boyd Hill LO
Dow Butte LO
Laufman RS
Susanville RS
Observation Mountain
Ravendale
Colby Mountain LO
Inskip
Boulder Creek GS
Camel Peak LO
Almanor RS
Greenville RS
Mohawk GS
Quincy HQ
Smith Peak LO
Chilcoot
Lexington
SAWMPK
Saddleback LO
=
=
=
=
=
=
=
=
=
=
=
=
=
Breckenridge
Forest Fire Station
Fire Station
Guard Station
Headquarters
Lava Beds
Lookout
Milk Ranch
Ranger District
Ranger Station
Saw Mill Peak
Weather Bureau Office
Whiskeytown
No.
Years
40202
40213
40214
40216
40217
40220
40221
40226
40233
40301
40302
40303
40305
40306
40307
40601
40603
40606
40607
40608
40609
40611
40613
40618
40701
40702
40703
40704
40706
40709
40711
40713
40714
40801
40803
40902
40903
40904
40905
40907
40910
40911
40913
40914
41206
41304
19
12
9
21
20
18
19
18
6
11
18
21
11
18
12
19
20
11
19
19
19
6
8
10
8
19
20
9
20
19
15
12
12
20
6
18
14
20
16
16
19
18
19
5
6
17
Observations
2460
1213
1453
3679
5248
2390
2536
1857
525
1755
2120
5386
1430
2558
1263
2745
4636
1541
2279
2957
2487
922
924
1284
1170
2512
2939
1150
2876
2989
2428
1352
1434
2611
849
2161
1733
3868
2581
2541
5091
2276
2520
525
817
1954
Figure 3--Section 2.
Stations in Section 2:
Station
Gasquet RS
Ship Mountain
Bald Mountain
Blue Ridge LO
Callahan RS
Crawford Creek GS
Forks of Salmon GS
Fort Jones RS
Happy Camp RS
Oak Knoll RS
Sawyers Bar
Seiad RS
Somesbar
Okonom Lookout
Parcgy
Collins Creek Baldy LO
Brush Mountain LO
Hoopa
Schoolhouse Peak LO
Willow Creek
Eel River
Big Bar RS
Coffee Creek RS
Hayfork RS
Hyampom GS
Limedyke LO
Mad River RS
Ruth RS
Weaverville RS
Harrison Gulch RS
WHSHQD
Eagle Peak LO
Saddle Camp GS
Eel River RS
Alder Springs
Figure 4--Section 3.
No.
Years
40102
40105
40201
40203
40204
40205
40208
40209
40211
40218
40222
40224
40231
40232
40234
40237
40404
40408
40413
40420
40421
40501
40502
40503
40504
40506
40507
40508
40510
40604
40628
40802
40809
41005
41101
20
7
5
19
20
17
17
16
11
20
21
18
16
15
6
9
20
8
15
13
8
20
20
20
18
19
20
18
20
20
9
20
10
20
20
Observations
2811
787
642
2452
3747
2221
2288
4592
1763
4718
4288
3761
2838
1742
809
1202
2691
1197
1765
2629
1108
3310
3110
3404
2428
2714
3062
2301
5030
3420
1439
2634
1151
2833
2827
Stations in Section 3:
Station
No.
Dog Valley
Challenge RS
Truckee RS
White Cloud
Duncan Peak GS
Forest Hill FS
Stateline LO
Armstrong Hill LO
Bald Mountain LO
Georgetown RS
Meyers RS
Markleeville
Blue Mountain LO
Fowler
Groveland RS
Mt. Elizabeth LO
Pine Crest RS
Woods Ridge LO
Bridgeport RS
Lee Vining
Walker
Crane
Jerseydale FFS
Wawona
Miami
Valley
Minarets RS
North Fork RS
Batterson RS
41302
41701
41804
41806
41901
41902
41904
42601
42603
42606
42607
42802
43203
43204
43603
43605
43606
43609
43702
43703
43707
44102
44105
44109
44110
44111
44203
44204
44207
Years
Observations
18
19
20
7
18
20
20
18
19
20
20
18
14
13
20
20
20
17
18
20
7
9
18
9
10
4
20
20
10
2460
2997
4343
1025
2059
4080
2583
2491
2892
5837
4582
2831
1792
1631
5343
2862
3091
2281
3436
5426
936
1335
3454
1329
1453
621
2795
6034
1991
5
Figure 5--Section 4.
Stations in Section 4:
Station
Howard Forest FFS
High Glade LO
Soda Creek GS
Konocti
Stonyfork RS
Mt. Jackson LO
St. Helena
Woodacre FS
6
Figure 6--Section 5.
No.
41007
41402
41406
41407
41503
42004
42106
42302
Years
Observations
15
17
20
9
20
8
8
8
1928
2245
2918
1240
6066
992
1087
1056
Stations in Section 5:
Station
Mammoth RS
Bald Mountain LO
Fence Meadow GS
Mountain Rest
Pinehurst RS
Trimmer
Delilah LO
Kaiser
Ash Mountain
Grant
Park Ridge
Wishon
MLKRCH
Cedar
Lone Pine RS
Round Valley
No.
Years
43704
43706
44503
44505
44508
44510
44512
44513
44701
44705
44713
44717
44718
44719
44802
44803
20
8
20
10
20
10
10
5
21
5
14
10
6
6
20
18
Observations
3831
1039
3068
1630
4076
2273
1425
573
3398
669
1605
1309
731
892
3863
4835
Figure 7--Section 6.
Stations in Section 6:
Station
Corralitos
Eagle Rock
Burrell
Arroyo Seco GS
Big Sur GS
Chews Ridge LO
Cone Peak LO
The Indians
Figure 8--Section 7.
No.
43802
43803
43806
44301
44302
44305
44306
44313
Years
Observations
Stations in Section 7:
Station
No.
6
13
5
20
19
19
19
19
899
1807
550
5265
3577
2789
2754
2517
Branch Mountain LO
Pozo GS
Figueroa GS
Los Prietos RS
Monastery
Casitas
Ozena
Rose Valley
44901
44908
45101
45103
45111
45208
45210
45211
Years
19
19
19
19
5
16
10
9
Observations
2829
3703
3746
5730
939
2417
1718
1613
7
Figure 9--Section 8.
Stations in Section 8:
Station
Bald Mountain
Uhl
Camp Whitsett
Tobias
Chimny
Democrat Springs
Kernville FS
BRKRDG
Chuchupate
Temescal RS
Big Pines
Chatsworth FS
Clear Creek FS
Duarte FS
Lechuza FS
Little Tujunga GS
Padua Hills FS
Sierra Pelona LO
Tanbark
Vallyermo RS
Vetter LO
Vincent FS
Warm Springs LO
Slide Mountain
Newhall
8
Figure 10--Section 9.
No.
44702
44712
44715
44716
44721
45002
45005
45009
45201
45207
45301
45304
45305
45306
45310
45311
45316
45318
45321
45323
45324
45325
45326
45328
45330
Years
18
16
8
10
4
19
20
5
19
20
19
8
10
13
8
19
17
19
10
20
19
17
20
8
8
Observations
2629
4346
921
1322
512
3050
4286
611
6055
3859
4501
1338
2092
2325
1166
3913
4124
2982
1415
4793
2546
4389
3401
994
1274
Stations in Section 9:
Station
Fawnskin
Big Pine Flats GS
Converse GS
Lytle Creek RS
Mill Creek RS
Strawberry Peak LO
Rock Camp RS
Devore
Mormon Rocks
Banning GS
Cranston GS
Keenwild GS
Kenworthy GS
Red Mountain LO
Temescal GS
Vista Grande GS
Alpine GS
Cameron GS
Descanso RS
Julian FFS
Laguna GS
Oak Grove RS
Pine Hills GS
Tenaja GS
Ramona
No.
45401
45402
45405
45408
45409
45410
45411
45413
45414
45601
45603
45604
45605
45608
45611
45612
45701
45704
45707
45708
45709
45710
45711
45715
45720
Years
20
18
19
20
20
19
18
9
10
18
19
20
19
19
20
16
20
20
20
16
20
20
20
20
9
Observations
6162
2937
3646
6304
6388
3362
3037
2445
1948
3394
3645
5392
3241
2855
4652
2776
4085
4071
6273
3292
3645
5732
3588
3819
2357
APPPENDIX B—Figure 11, Tables 1 to 18
Figure 11--Information for Mount Hebron Ranger Station.
Table 1 --Percent probability of n consecutive days of spread component remaining in or becoming greater
than initial range for 1300 P.s.t.
Mount Hebron RS 40216
Model: G
Observations: 1374
Slope class: 2 Vegetation type: P
Years of record: 9
9
Table 2--Cumulative percent probability of spread component occurrence by class and month and minimum and
maximum by month for 1300 P.s.t.
Mount Hebron RS
40216
Years of record: 9
Month
Spread
component
Jan.
Feb.
0-5
6-10
11-20
21-40
41-80
81-160
161-320
321-640
641-1000
1001+
Maximum
Minimum
Observations
0
0
Mar.
Apr.
0
May
June
July
Aug.
Sept.
Oct.
Nov. Dec.
100
83
40
9
0
0
0
0
0
0
34
3
149
100
63
18
2
0
0
0
0
0
0
31
0
263
100
72
18
1
0
0
0
0
0
0
29
1
272
100
68
20
4
0
0
0
0
0
0
41
1
271
100
68
24
6
0
0
0
0
0
0
39
0
254
100
80
17
5
1
0
0
0
0
0
49
3
143
100
55
9
0
0
0
0
0
0
0
12
3
11
100
100
73
55
9
0
0
0
0
0
60
6
11
0
Obs.
398
673
242
57
4
0
0
0
0
0
1374
Table 3--Percent probability of n consecutive days of burning index remaining in or becoming greater than
initial range for 1300 P.s.t.
Mount Hebron RS 40216
Observations: 1374
Model: G
Slope class: 2
Vegetation type: P
Years of record: 9
Length of run (days)
Burning
index
0
0-15
16-30
31-35
36-40
41-50
51-60
61-70
71-80
81-90
91+
100
100
100
100
100
100
100
100
100
100
1
100
95
74
65
48
29
24
26
5
17
2
3
4
5
6
100
90
63
49
33
16
5
0
0
0
100
86
51
36
22
9
2
0
0
0
100
81
45
26
16
5
0
0
0
0
100
81
38
21
11
3
0
0
0
0
100
76
32
19
8
2
0
0
0
0
7
8
100
71
27
17
7
1
0
0
0
0
100
71
24
16
6
0
0
0
0
0
Obs.
9
100
71
23
15
5
0
0
0
0
0
16
220
220
260
372
171
66
23
19
7
Table 4--Cumulative percent probability of burning index occurrence by class and month and minimum and maximum by
month for 1300 P.s.t.
Mount Hebron RS
40216
Years of record: 9
Month
Burning
index
0-15
16-30
31-35
36-40
41-50
51-60
61-70
71-80
81-90
91+
Maximum
Minimum
Observations
10
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov. Dec.
Obs.
0
0
0
100
100
100
100
91
64
64
55
27
18
114
38
11
100
99
81
62
44
19
5
1
0
0
78
15
149
100
99
76
56
40
15
5
3
2
0
90
0
263
100
100
91
83
60
21
8
2
1
0
90
12
272
100
97
86
71
59
33
13
6
3
1
94
1
271
100
99
77
61
45
19
7
4
2
1
97
0
254
100
100
87
61
28
10
6
3
1
0
85
19
143
100
100
55
36
9
0
0
0
0
0
45
20
11
16
220
220
260
372
171
66
23
19
7
1374
0
Table 5-- Percent probability of n consecutive days of ignition component remaining in or becoming greater
than initial range for 1300 P.s.t.
Mount Hebron RS 40216
Observations: 1374
Model: G
Slope class : 2 Vegetation type:
Years of record: 9
P
Length of run (days)
Ignition
component
0
1
2
3
4
5
6
7
8
9
Obs.
0-10
11-20
21-30
31-40
41-50
51-60
61-70
71-80
81-90
91-100
100
100
100
100
100
100
100
100
100
100
100
81
70
48
31
16
27
0
0
0
100
65
56
34
13
6
0
0
0
0
100
61
42
21
6
0
0
0
0
0
100
54
35
12
4
0
0
0
0
0
10
48
30
7
1
0
0
0
0
0
100
44
25
5
0
0
0
0
0
0
10
44
21
4
0
0
0
0
0
0
100
40
19
3
0
0
0
0
0
0
10
38
16
3
0
0
0
0
0
0
175
295
456
285
101
34
17
8
3
0
Table 6--Cumulative percent probability of ignition component occurrence by class and month and minimum and
maximum by month for 1300 P.s.t.
Mount Hebron RS
Ignition
component
0-10
11-20
21-30
3140
41-50
51-60
61-70
71-80
81-90
91-100
Maximum
Minimum
Observations
40216
Jan.
0
Years of record: 9
Feb. Mar.
Apr.
May
Month
June
July
0
100
100
100
82
36
27
9
0
0
0
67
22
11
100
80
48
19
5
2
1
0
0
0
64
0
149
100
82
57
22
7
3
1
0
0
0
84
0
263
0
100
94
75
42
15
4
1
1
0
0
84
0
272
Aug
100
89
73
40
18
8
4
1
0
0
89
0
271
Sept.
Oct.
100
87
67
37
13
5
3
1
0
0
78
0
254
100
89
69
25
6
3
1
1
0
0
72
0
143
Nov. Dec.
100
64
18
0
0
0
0
0
0
0
28
2
11
0
Obs.
175
295
456
285
101
34
17
8
3
0
0
0
1374
Table 7--Cumulative percent probability of temperature occurrence by class and month and minimum and maximum by
month for 1300 P.s.t.
11
Table 8--Temperature means and record highs and lows for the period of record after 1972 Mount Hebron RS
40216
Years of record: 9
Month
Temperature
(° F)
Record high
Mean maximum
Mean
Mean minimum
Record low
Observations
Jan.
0
Feb.
0
Mar
0
Apr.
May
Jun
July
Aug.
Sept
Oct
Nov
Dec.
76
66
47
29
14
11
84
65
49
32
11
149
92
75
57
39
19
263
97
83
64
44
13
272
102
81
61
41
27
271
92
77
56
36
17
254
88
70
48
27
9
143
69
55
32
10
-4
11
0
Table 9--Cumulative percent probability of relative humidity occurrence by class and month and minimum and maximum by,
month for 1300 P.s.t.
Mount Hebron RS
Relative
humidity
(pct)
0-9
10-19
20-29
30-39
40-49
50-59
60-69
70-79
80-89
90-100
Maximum
Minimum
Observations
40216
Years of record: 21
Month
Jan.
100
100
100
93
82
71
68
46
18
0
88
25
28
Feb.
Mar.
100
100
100
93
86
59
38
28
10
0
88
26
29
100
100
96
79
60
44
23
15
8
0
84
14
52
Apr
100
99
79
48
30
19
14
8
5
1
92
9
113
May
June
100
99
88
60
33
19
8
5
2
1
100
5
389
100
100
90
55
29
15
9
5
2
0
100
8
612
July
100
99
75
28
8
4
1
0
0
0
89
5
644
Aug.
Sept.
Oct. Nov.
Dec.
Obs.
100
99
75
35
14
8
4
2
1
0
90
6
638
100
100
77
40
19
9
5
3
2
0
100
6
614
100
100
85
56
32
18
9
5
2
1
100
9
421
100
100
98
88
70
52
28
18
8
3
100
13
108
100
100
100
97
87
67
37
13
3
3
93
28
30
20
640
1292
815
379
243
117
88
67
17
Table 10--Relative humidity means and record highs and lows for the period of record after 1972
Mount Hebron RS
40216
Years of record: 9
Relative
humidity
(pct)
Record high
Mean maximum
Mean
Mean minimum
Record low
Observations
12
Month
Jan.
Feb.
Mar
Apr.
May
June
July
Aug.
Sept.
Oct .
Nov
Dec.
0
0
0
100
69
43
17
8
11
100
93
63
33
8
149
100
91
61
30
8
266
100
88
57
25
7
273
100
91
58
26
6
272
100
94
61
28
5
254
100
96
61
27
9
142
100
94
66
37
11
11
0
3678
Table 11-- Cumulative percent probability of 1-h TLFM occurrence by class and month and minimum and maximum by
month for 1300 P.s.t.
Mount Hebron RS
40216
Years of record: 21
Month
1-h TFLM
(pct)
Jan.
Feb.
Mar.
Apr.
May
June
0-1
2-3
4-5
6-7
8-9
10-II
12-13
14-15
16-17
18+
Maximum
Minimum
Observations
100
100
100
86
79
57
32
21
18
7
26
5
28
100
100
100
97
76
48
31
24
21
14
19
5
29
100
100
98
85
46
27
21
12
8
2
18
3
52
100
100
88
49
27
18
12
8
5
4
26
2
113
100
100
94
60
36
19
11
5
3
2
26
2
389
100
100
93
51
27
16
9
6
5
4
28
2
582
July
100
100
76
22
7
3
1
1
0
0
21
2
613
Aug.
Sept.
Oct.
Nov.
100
100
75
27
12
7
4
2
2
1
26
2
605
100
100
78
32
14
8
5
3
2
1
28
2
584
100
100
91
52
26
14
8
5
4
3
31
2
401
100
100
99
91
65
38
22
15
12
7
32
3
108
Dec.
Obs.
100
100
100
97
73
43
10
7
7
7
26
5
30
0
543
1487
718
338
192
101
36
37
82
3534
Table 12--Cumulative percent probability of 10-h TLFM occurrence hr class and month and minimum and maximum by
month for 1300 P.s.t.
Mount Hebron RS
40216
Years of record: 21
Month
10-h TLFM
(pct)
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
0-1
2-3
4-5
6-7
8-9
10-11
12-13
14-15
16-17
18+
Maximum
Minimum
Observations
0
0
0
100
100
100
100
91
64
27
0
0
0
12
7
11
100
100
99
94
78
51
32
22
15
11
46
3
389
100
100
100
92
64
41
26
17
13
10
50
3
582
100
100
98
65
27
15
7
3
2
1
35
3
613
100
100
97
59
28
18
10
7
5
4
50
2
605
100
100
99
64
37
21
12
8
6
5
50
2
584
100
100
99
86
64
42
27
17
10
6
50
3
401
100
100
100
98
97
88
69
41
30
19
50
5
108
Dec.
100
100
100
100
100
97
77
60
33
10
38
9
30
Obs.
0
47
766
937
599
435
271
147
94
238
3534
Table 13--Cumulative percent probability of 100-h TLFM occurrence by class and month and minimum and maximum by
month for 1300 P.s.t.
Mount Hebron RS
40216
Years of record: 9
Month
100-h TLFM
Jan.
(pct)
0-1
2-3
4-5
6-7
8-9
10-11
12-13
14-15
16-17
18+
Maximum
Minimum
Observations
0
Feb.
Mar.
0
0
Apr.
100
100
100
100
91
64
27
0
0
0
12
7
11
May
100
100
100
100
100
100
95
70
31
14
25
10
149
June
100
100
100
100
100
93
76
41
17
5
22
7
266
July
100
100
100
100
99
88
62
24
4
1
20
7
273
Aug.
100
100
100
100
98
84
71
50
20
7
36
7
272
Sept.
100
100
100
100
100
100
95
83
46
19
32
9
254
Oct.
100
100
100
100
I00
100
100
97
85
36
23
12
143
Nov.
100
100
100
100
100
100
100
100
100
64
20
16
11
Dec.
100
100
100
100
100
0
Obs.
0
0
0
11
89
177
330
364
246
162
1379
13
Table 14--Cumulative percent probability of 1000-h TLFM occurrence by class and month and minimum and maximum by
month for 1300 P.s. t.
Mount Hebron RS
40216
Years of record: 9
Method
1000-h TLFM
(PC )
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug
Sept
Oct
Nov.
0-1
2-3
4-5
6-7
8-9
10-11
12-13
14-15
16-17
18+
Maximum
Minimum
Observations
0
0
0
100
100
100
100
100
100
100
100
100
36
19
16
11
100
100
100
100
100
100
100
100
99
68
22
15
149
100
100
100
100
100
100
100
88
52
26
20
11
266
100
100
100
100
100
100
93
50
12
3
18
11
273
100
100
100
100
100
100
66
38
17
10
28
10
272
100
100
100
100
100
100
100
76
48
28
25
12
254
100
100
100
100
100
100
100
100
79
42
22
15
143
100
100
100
100
100
100
100
100
100
91
18
17
11
Dec
Obs.
-
0
0
0
0
0
112
285
359
272
351
0
1379
Table 15--Cumulative percent probability of woody fuel moisture occurrence by class and month and minimum and
maximum by month for 1300 P.s.t.
Mount Hebron RS
40216
Years of record: 9
Month
Moisture
(pct)
0-29
30-59
60-89
90-119
120-149
150-179
180-209
210-239
240-269
270+
Maximum
Minimum
Observations
Jan.
0
Feb
0
Mar
Apr
0
100
100
100
0
0
0
0
0
0
0
60
60
11
May
100
100
100
46
17
3
0
0
0
0
160
60
149
June
July
Aug.
Sept
Oct
Nov
Dec.
Obs.
100
100
100
99
57
3
0
0
0
0
158
89
266
100
100
100
93
14
0
0
0
0
0
145
82
273
100
100
100
66
19
7
6
0
0
0
200
74
272
100
100
100
64
33
10
0
0
0
0
180
60
254
100
100
100
5
5
0
0
0
0
0
140
60
143
100
100
100
0
0
0
0
0
0
0
60
60
11
0
0
0
443
580
299
39
18
0
0
0
1379
Table 16--Cumulative percent probability of herbaceous fuel moisture occurrence by class and month and minimum and
maximum by month for 1300 P.s.t.
Mount Hebron RS
40216
Years of record: 9
Month
Moisture
(pct)
0-29
30-59
60-89
90-119
120-149
150-179
180-209
210-239
240-269
270+
Maximum
Minimum
Observations
14
Jan.
Feb.
Mar.
0
0
0
Apr.
May
June
100
0
0
0
0
0
0
0
0
0
9
3
11
100
61
45
29
15
5
1
0
0
0
180
4
149
100
100
100
100
53
11
0
0
0
0
176
89
266
July
100
100
100
78
1
0
0
0
0
0
121
73
273
Aug.
Sept
100
100
100
38
7
6
0
0
0
0
150
59
272
100
64
64
39
6
1
0
0
0
0
150
3
254
Oct.
100
5
5
5
0
0
0
0
0
0
100
2
143
Nov
100
0
0
0
0
0
0
0
0
0
15
4
11
Dec.
Obs.
-
308
25
319
529
141
56
1
0
0
0
0
1379
Table 17--Precipitation (inches)
Mount Hebron RS
40216
Month
Year
Jan.
Feb.
Mar.
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
-
-
-
Mean
-
-
-
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov
Dec.
Total
-
1.00
-
1.65
0.56
0.78
1.63
0.69
2.02
0.83
1.14
1.52
0.39
0.00
0.05
0.77
1.24
0.25
1.30
0.22
inches
0.14
0.31
0.33
0.26
0.11
0.01
0.00
0.33
0.22
0.07
0.02
1.06
0.13
0.78
0.07
0.58
0.13
-
0.53
0.25
0.11
0.93
0.00
0.00
0.00
0.11
0.13
0.11
3.05
1.40
0.00
0.18
0.69
0.30
0.08
0.12
0.02
0.55
0.16
0.08
0.17
0.00
0.64
0.47
0.00
0.48
-
0.10
0.00
0.17
0.88
1.65
-
-
-
-
-
1.00
0.88
0.27
0.49
0.27
0.56
-
-
-
Table 18--Percent probability of joint occurrence of windspeed and
direction at 1300 P.s.t.
REFERENCES
Deeming, John E., Burgan, Robert E.; Cohen, Jack D. The National
Fire-Danger Rating System--1978. Gen. Tech. Rep. INT-39. Ogden,
UT: Intermountain Forest and Range Experiment Station, Forest
Service, U.S. Department of Agriculture; 1977. 63 p.
Furman, R. William; Brink, Glen E. The National Fire Weather Data
Library: what it is and how to use it. Gen. Tech. Rep. RM-19. Fort
Collins, CO: Rocky Mountain Forest and Range Experiment Station,
Forest Service, U.S. Department of Agriculture; 1975. 8 p.
Main, William A.; Straub, Robert J.; Paananen, Donna M. FIREFAMILY: fire planning with historic weather data. Gen. Tech. Rep.
NC-73. St. Paul, MN: North Central Forest Experiment Station,
Forest Service, U.S. Department of Agriculture; 1982. 31 p.
15
Ryan, Bill C. Potential fire behavior in California: an atlas and guide for forest and
brushland managers. Gen. Tech. Rep. PSW-77. Berkeley, CA: Pacific Southwest
Forest and Range Experiment Station, Forest Service, U.S. Department of Agri­
culture; 1984. 15 p.
Potential fire characteristics can be estimated as functions of weather, fuel, and
terrain slope. Such information is needed by forest and other land managers-­
especially for anticipating fire suppression needs and planning prescribed burns. To
provide this information, an Atlas has been developed for California. The Atlas
includes statistical analyses of spread component, burning index, ignition component,
temperature, relative humidity, dead fuel moisture, live woody fuel moisture, live
herbaceous fuel moisture, precipitation, windspeed and direction for 200 fire-danger
rating stations in California. Charts and information for one of the stations included in
the Atlas--Mount Hebron in northern California--serve as an example of this
application.
Retrieval Terms: fire management, prescribed burning, fuel moisture, forest climatol­
ogy, potential fire characteristics