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NTFB - What it needs (inputs)

Like other fire behavior models, WFDSS Near-Term Fire Behavior (NTFB) requires the following data to perform fire behavior calculations: 

WFDSS provides much of the necessary information to perform fire spread and fire behavior calculations. The Fire Behavior Specialist (FBS) can adjust most inputs (weather, winds, and landscape data) as needed. The following table lists the inputs required for the WFDSS Near-Term Fire Behavior model:

Table 1: Inputs Required for a Near-Term Fire Behavior Model

Input

Source

Comments

Landscape extent

 

FBS-defined

(required)

The FBS draws the landscape extent (normally no more than 5-6 miles per side) on the Analysis Map page.

Landscape Data Source

WFDSS

You can choose to use the default LANDFIRE 2010 1.2.0 landscape data source or select a different data source from the Landscape page.

In addition, you can modify landscape data layers using the Landscape Editor.

Analysis Name

FBS-defined

Limited to 48 characters, do not use underscores. The analysis name cannot contain an apostrophe or backslash; the cursor blinks if you try to add these characters and a message displays that these characters are disabled. Can edit until analysis is submitted.

Conditioning Days

The default conditioning period is 7 days before the analysis start date

Choose the number of days, but use at least 5 days so the 100-hour time lag fuels can be fully "conditioned".

Spotting Probability

 

Default 0.00%

Entered as a decimal value from 0 to .15 (.15 equals 90-100% Probability of Ignition in NTFB).

Spot Ignition Delay

Default of zero minutes

The amount of time that passes between a spot landing and fire spread occurring.

Crown Fire Method

Finney (1998) or Scott-Reinhardt (2001)

The Finney crown fire model is the default for the BFB, STFB, NTFB and FSPro models.

For recent versions of LANDFIRE (2010, 2014) canopy bulk density values were computed to produce more active crown fire when using the Scott and Reinhardt model compared to the Finney crown fire model. You would expect to see slower rates of spread and less fire intensity for predicted passive crown fire when using Finney versus Scott and Reinhardt crown fire models. Whatever crown fire model you choose, it is important to calibrate your simulated fire behavior to observed fire behavior.

Foliar Moisture Content (%)

WFDSS Default is 100%

Using 100% foliar moisture is adequate to depict a normal year; however, you can modify this value as needed.

Analysis Start Date and Time

FBS-defined

The date and time you want to start the analysis.

Analysis End Date and Time

FBS-defined

The date and time you want the analysis to end. Limited to no more than 15 days beyond the start date.

Ignition File

FBS-defined

(required)

Choose the ignition file from a drop-down list.

Barrier File

FBS-defined

(optional)

If needed, FBS chooses the barrier file from the drop-down list. You can fill the barrier (make the interior of the ignition unburnable) or not based on associated radio buttons.

Remotely Automated Weather Station (RAWS)

WFDSS selects a RAWS based on the following criteria:

  • Identifying the center of the landscape extent
  • Calculating the distance from the center to the nearest RAWS(s) using a horizontal/vertical (elevation) algorithm
  • ranking the stations
  • selecting the station that is “closest” and has weather data requisite for fuel moisture conditioning (at least 7 days)

WFDSS selects the "closest" RAWS, but you can choose a different station if needed. The FBS can select fewer conditioning days and a different weather station that has weather data requisite for the conditioning days selected.

Loading the RAWS KML (from left-hand menu) into Google Earth gives you insight into which RAWS would be most appropriate for your analysis.

Burn period dates and hours

FBS-defined

Decide the dates and the number of hours for each analysis date during which you want to model active fire behavior. Default hours are for a 24-hour burn period, but you should generally pick a shorter timeframe, as a full day of spread is likely to greatly overpredict growth during the overnight hours. Analyses of more than three days are not recommended unless the weather is stable with a very reliable forecast beyond that time period.

Initial Fuel Moisture inputs

NFDRS dead fuel calculations for the beginning of the conditioning period and GSI live fuel calculations for the start of the first burn period.

Select dead fuel moistures for the start of the conditioning period and adjusted accordingly before starting the modeled ignition.

Because the live fuel moistures (herbaceous and woody) are not affected by fuel moisture conditioning, critique these values and change as appropriate. You can enter different fuel moistures for some or all of the fuel models in the landscape.

Hourly Weather Records

The Weather Summary Table displays several days (rows) of daily weather summaries. Hourly data can be viewed and edited by selecting a date and clicking the  'Hourly Records' button below the table. The following hourly inputs are used by NTFB:

  • Precipitation amount
  • Temperature
  • Relative Humidity
  • Wind Speed
  • Wind Direction
  • Cloud Cover % (used as part of shading calculation for conditioning fuels)

 

Change any of these values as needed.

 

Values that are uneditable are not being used by the model (for example, wind speed during the conditioning period).

 

The 'Record Type' column indicates if the data is coming from a RAWS or from forecasted weather.

 

Gridded winds are currently not used in NTFB, but they will likely be added as future enhancement.

 

Timestep

Not visible to FBS (in inputs)

In the FARSITE model, analysts could adjust the modeled and visible timesteps. In NTFB, these settings are set at one hour. Though you cannot adjust the input timestep, you can select several options for output timesteps once the run is complete. Slow-moving fires may not display well with a one-hour timestep and you might need to select a longer duration timestep (in the outputs) to get the desired display for the modeled progression.

Perimeter and Distance Resolution

Not visible to FBS and cannot be adjusted.

In FARSITE, analysts could set these values. In NTFB, they are 'hard-coded' and cannot be manually adjusted. Distance and perimeter resolution are set at the landscape resolution. However, the minimum perimeter resolution is 60 meters. For example, running NTFB on a 30-meter landscape means that distance resolution is 30 meters and perimeter resolution is 60 meters. If an analysis is taking too long at 30 meters, you can copy the NTFB inputs to a new run with a lower/coarser resolution landscape (higher number). This speeds processing time, but reduces the detail and accuracy of the output. 

Minimum Spotting Distance

Not visible to FBS and cannot be adjusted. Set at landscape resolution.

When FARSITE was developed, computer processing times limited the ability to calculate spotting. NTFB allows you to set spotting percentages at a much higher level (theoretically up to 100%).  Most NTFB modeled spots are 'near distance' and appear to have little impact on the final modeled fire perimeter or fire behavior outputs; the ground fire simply overruns these spots.  Processing time, however, is considerable as the model 'untangles the spaghetti' that is created from near-distance spot growth. For these reasons, the minimum spotting distance (set to the landscape resolution) essentially skips the first 'cell'.  For example, on a 60-meter landscape, no spots occur in the first 60 meters from the perimeter, but any viable embers that land beyond 60 meters can produce spot fires.

* WFDSS chooses the nearby RAWS in the following way:  The ignition location is used as a starting point.  Then, a horizontal/vertical distance algorithm sorts the RAWS stations within a given area.  Next, WFDSS iterates through the list until the first station is found with the requisite fuel moisture / weather information (continuous hourly observations).-----------
Last updated on 8/27/2019 11:46:06 AM.

In This Section

WFDSS Near-Term Fire Behavior Analysis (NTFB)

See Also

NTFB - What it is

NTFB - What it does (outputs)

NTFB - What it means (interpretation)

Analyst-Assisted NTFB - Why use it (potential uses)

NTFB - Assumptions and Limitations

Reference

Field Descriptions

Glossary Resources

Spatial Data Reference

Landscape Data Source Reference

Relative Risk Reference

Organization Assessment Reference

Fire Behavior Reference

About the WFDSS Decision Editors