Each day during the fire season, mid-afternoon fire weather observations (2 pm LDT) are taken from a network of fire weather stations located throughout the United States. The fire weather network is comprised of over 1000 weather stations across the Conterminous United States. In the state of Washington there are over 100 fire weather stations owned and operated by state and federal land management agencies. Fire weather observations are reported to the Weather Information Management System (WIMS) where they are combined with a station's fuel conditions and topography information and then processed by NFDRS algorithms to generate the various NFDRS indices and components that describe today's fire danger in a particular rating area. NFDRS observed indices and components are used on a daily basis by wildland fire managers to determine the strength and placement of fire suppression resources, to determine fire suppression actions, to ensure firefighter safety, fire prevention, fire planning for allocation of the fire budget, prescribed burning operations, and in the regulation of public and industrial use and access of forest and range land. (See NFDRS applications on main menu). Each afternoon during the fire season, NWS fire weather forecasters analyze the available fire weather observations for their district in preparation for generating NFDRS zone trend forecasts.

Beside the Fire management community, other natural resource managers use the daily fire weather observations for such things as avalanche forecasting, wetland determinations, seeding projects, air quality studies, smoke management, recreation studies, etc. Other users of fire weather observations may be people outside of your agency who access fire weather data through the Western Regional Climate Center or the National Weather Service. The table below shows a portion of a typical AFOS file which lists the available 2pm fire weather observations from fire weather zone 659 in the Olympia Fire Weather district.

Example Fire Weather Observation File





NMCFWOOLM:
SXUS45 KMWI 112145
Weather Information Management System
USDA National Computer Center
11-Aug-97 21:45:45 GMT



Listing of Observations for (OLYMPIA)

ST NME	STAT'N	DATE	HR	T	W	DBT	DPT	RH	Y	M	DIR	WS	10	TMX	TMN	HMX	HMN	PD	PPAMT

Zone: 659
KOSMOS	451105	970811	13	O	O	81	55	42	1	1	194	5	6	85	61	63	29	0	0.00
LONGMI	451106	970811	13	O	1	80	53	40	1	1	135	6	4	80	47			0	0.00
HAGAR	451115	970811	12	O	1	80	55	43	1	1	289	6		81	55	80	30	0	0.00
OHANAP	451119	970811	13	O	O	87	52	31	1	1	225	10	6	93	45			0	0.00
LESTER	451705	970811	13	O	O	86	50	30	1	1	237	8		90	46	100	4	0	0.00
STAMPE	451711	970811	13	O	O	75	47	38	1	1	270	6		75	58			0	0.00
GREENW	451718	970811	13	O	O	90	59	36	1	1	228	10		92	53	94	25	0	0.00
ORRCR	451919	970811	12	O	1	89	54	31	1	1	283	6		89	48	100	23	0	0.00

Count:	8	Zone Average:				84	53	36				7	5	86	52	87	22	0	0.00

The list below contains explanations of the individual data elements listed above in the AFOS file NMCFWOOLM. Items marked with an asterisk (*) are not absolutely necessary.

Station Name (ST NME)

Station Number (STAT'N)

Current Date (DATE)

Hour of the Observation (HR)

Type of Observation (T)

(O) = Observed, (F) = Forecast

State of Weather (W)

A one-digit code number describing the weather at the time of the observation.

0		- Clear, less than 1/10th cloud cover
1		- Scattered clouds, 1/10-5/10 cloud cover
2		- Broken clouds, 6/10-9/10 cloud cover
3		- Overcast, 10/10 cloud cover
4		- Fog
5		- Drizzle or mist
6		- Rain
7		- Snow
8		- Showers
9		- Thunderstorms

Notes:

An "8" should be used when showers are in sight or occurring at the observing weather station.

Thunderstorms in progress (lightning seen or thunder heard) should be recorded by stations having unrestricted visibility (i.e., lookouts) only when the activity is not more than 30 miles away.

States of the Weather 5, 6, or 7 (i.e., drizzle, rain or snow) will set the "fuels-wet" flag to "Y", which causes key NFDRS components and indexes to be set to zero because generalized precipitation over the entire forecast area is assumed. States of Weather 8 and 9 assume localized precipitation and will not set the "fuels-wet" flag to "Y".

Dry Bulb Temperature (DBT)

The observed dry bulb temperature to the nearest whole degree.

Humidity (RH)

For manual fire weather stations the traditional humidity entry is the wet bulb temperature. Relative humidity is the standard entry for RAWS stations.

Yesterday's LAL (Y)

A one-digit number that best describes the lightning situation from midnight yesterday to midnight last night. (See table below).

Today's Lightning Activity Level (M)

A one-digit code that best describes the lightning activity from midnight last night to basic observation time today. Note: This is for a 30-mile radius of the weather station.

1		No thunderstorms or building cumulus clouds observed.

2		Infrequent lightning. A single to a few building cumulus clouds with only an occasional one reaching thunderstorm intensity. Thunderstorms or lightning need not be observed for this activity level; however, at least on large cumulus clouds must be present.

3		Occasional lightning (1-2 cloud-to-ground strikes per minute). Building cumulus are common; thunderstorms are widely scattered.

4		Frequent lightning (2-3 cloud-to-ground strikes per minute). Thunderstorms are common and cover 20-30% of the sky. Lightning is primarily cloud-to-cloud or cloud-to-ground, but cloud-to ground lightning is observed.

5		Frequent and intense lightning (cloud-to-ground strikes > 3 per minute). Thunderstorms are common, occasionally obscuring the sky. Moderate to heavy rainfall with the thunderstorms and light to moderate rainfall preceding and following the storm. Lightning of all kinds occurs frequently and is characteristically persistent during the storm.

6		Low lightning flash rate (less than 1-3 strikes in a 5 minute period). Scattered towering clouds with a few thunderstorms. Bases of the clouds are high; virga is the most predominate form of precipitation.

Wind Direction* (Dir)

Reported either as the degrees or the alpha code from which the wind is blowing at the time of the observation. RAWS stations default to degrees. The reported values represents the 10-minute average wind directions that corresponds to the same period as the wind speed.

16	N - North	360
1	NNE - North Northeast	23
2	NE - Northeast	45
3	ENE - East Northeast	68
4	E - East	90
5	ESE - East Southeast	113
6	SE - Southeast	135
7	SSE - South Southeast	158
8	S - South	180
9	SSW - South Southwest	203
10	SW - Southwest	225
11	WSW - West Southwest	248
12	W - West	270
13	WNW - West Northwest	293
14	NW - Northwest	315
15	NNW - North Northwest	338

A calm or no wind situation is identified by a "0" Wind Direction and a "0" Wind Speed. If wind direction information is not available, the field is left blank. AWind direction is not a required input parameter.

Wind Speed (WS)

The 10-minute average wind speed observed at the time of the daily observation in miles per hour. The reported values should represent the average wind speed at 20 feet above the ground or the surrounding vegetation.

10-hr Fuel Moisture* (10)

The measured moisture content of the 1/2- inch fuel moisture sticks to the nearest gram. The entry is left blank if the 10-hr fuel moisture value is unavailable; the danger -rating processor will calculate a value. The computed 10-hr fuel moisture value is a function of average temperature, humidity, and precipitation during the previous 24 hours. Computed values range from 1 to 35 percent, while measured values can range from 1 to 50 percent or higher. However, remember the moisture of extinction is 25 percent.

Maximum Temperature* (TMX)

Maximum temperature reported during the previous 24 hours. The maximum temperature cannot be lower than the dry-bulb temperature at the current observation time. If so, change the maximum temperature to the current dry-bulb temperature.

Minimum Temperature* (TMN)

Minimum temperature reported during the previous 24 hours. The minimum temperature cannot be higher than the dry-bulb temperature at the current observation time. If so, change the minimum temperature to the current dry-bulb temperature.

Maximum RH* (HMX)

Maximum relative humidity reported during the previous 24 hours. The maximum relative humidity cannot be lower than the relative humidity at the current observation time. If so, change the maximum relative humidity to the current relative humidity.

Minimum RH* (HMN)

Minimum relative humidity reported during the previous 24 hours. The minimum relative humidity cannot be higher than the relative humidity at the current observation time. If so, change the minimum relative humidity to the current relative humidity.

Precipitation Duration (PD)

The actual number of hours of precipitation during the previous 24 hours. The reported value should represent the total time fuels were exposed to rain since the last regular observation.

Notes:

A "0" duration is reported when no precipitation is observed in the 24 hours since the last observation time.

If a Trace of precipitation is reported, the duration must equal at least one hour.

Precipitation duration is extremely important in the calculation of 100- and 1000-hr fuel moisture values.

Precipitation Amount (PPAMT)

The actual amount of precipitation reported during the past 24 hours up to the current observation time. Amounts less than 0.005" are reported as a trace.

The precipitation amount is important in the daily computation of the Keetch-Bryram Drought Index (KBDI). The KBDI is reduced by one point for every 0.01 inches of precipitation.

Fuels Wet Flag (FW)

This entry indicates whether or not the fuels are wet at the observation time. The Fuels-Wet Flag is set to "Y" by the danger-rating processor if the State of Weather is 5, 6, or 7..

A Fuels-Wet Flag of "Y" causes the ignition component, spread component, energy release component, burning index, human- and lightning-caused occurrence indices and the fire load index to be set to zero (0). The 1-hr and 10-hr fuel moisture values are also set to 35% if no measured 10-hr fuel moisture stick value has been entered.

Observed Fire Danger

Remember, calculations of fire danger and/or fire behavior are based on information contained in the NFDRS station catalog about the fuels and topography of a given fire weather station, along with the observed or forecasted weather for that station. Shortly after land management agencies enter their 2pm fire weather observations into WIMS, NFDRS algorithms calculate the observed, or actual, fire danger for each station using the current 2pm weather observation and the catalogued information on fuels and topography. The actual fire danger for each station is described by the various components and indices calculated by the National Fire Danger Rating System. The table below shows a portion of a typical WIMS output file which lists the observed or current fire danger for each fire weather station which reported a weather observation that day.

Example Fire Danger Output (based on the fire weather observations listed above)




ST NME	STAT'N	DATE	HR	T	MSGC	WS	WDY	HRB	1H	10	HU	TH	IC	SC	EC	BI	FL	SL	R	KBDI

Zone: 659
KOSMOS	451105	081197	13	O	7G4P3	5	142	136	5	6	15	15	26	8	31	37	27	3-	M	57
LONGMI	451106	081197	13	O	7G2P3	6	129	125	5	4	16	17	20	5	33	31	22	3	M	57
HAGAR	451115	081197	12	O	7G3P3	6	138	93	7	8	15	18	20	7	30	34	24	3-	M	57
OHANAP	451119	081197	13	O	7G2P3	10	146	155	4	6	17	19	31	7	28	35	25	3	M	93
LESTER	451705	081197	13	O	7G3P3	8	143	135	4	6	16	19	31	8	29	36	26	3-	M	569
STAMPE	451711	081197	13	O	7G3P2	6	134	122	5	7	14	17	10	6	33	35	25	2	L	41
GREENW	451718	081197	13	O	7G4P3	10	142	147	5	7	16	19	35	11	28	42	31	3-	M	50
ORRCR	451919	081197	13	O	7G3P3	6	127	5	5	7	15	17	32	9	35	43	31	3+	M	100

The list below contains explanations of the individual data elements listed above.


ST NME - Station name
STAT'N - Station catalog number
DATE - Today's date
HR - Hour of the observation. Note.....this should match the time listed on the fire weather observation.
T - Type (O) observed (F) forecast.
MSGC - (M=Fuel Model...7G = 1978 NFDRS fuel models, 8G = 1988 NFDRS fuel models), (S=Slope...1 = 0-25%, 2 = 26-40%, 3 = 41-55%, 4 = 56-75%, 5 = >75%), (G=Grass type... P = perennials A = annuals), (C=Climate class... 1= arid, 2 = semiarid, 3 = subhumid , 4 = humid).
WS - Observed wind speed (miles/hour).
WDY - Woody fuel moisture (%).
HRB - Herbaceous fuel moisture (%).
1H - One hour timelag fuel moisture (%).
10 - Ten hour timelag fuel moisture (%).
HU - One hundred hour timelag fuel moisture (%).
TH - One thousand hour timelag fuel moisture (%).
IC - Ignition Component - the probability of ignition expressed as a unitless number. (0-100)
SC - Spread Component - the forward rate of spread of the flaming fire front at the head of the fire. (ft/min)
EC - Energy Release Component - the amount of heat energy per square foot within the flaming fire front. (BTUs per square foot)
BI - Burning Index - a dimensionless number that relates the contribution of fire behavior to the effort of containing a single fire.
FL - Fire Load Index - the total potential containment effort needed on a given day expressed as a dimensionless number. ( 0 - 100)
SL - Staffing Level. (1 - 5)
R - Adjective Rating
KBDI - Keetch Byram Drought Index. (0 - 800)

Please refer any questions or comments about this web site to: john.werth@noaa.gov