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Running a Near-Term Fire Behavior Analysis (NTFB)
This fire behavior model produces outputs that represent modeled growth in the form of a 'fire progression' (similar to the FARSITE desktop model). Unlike Short-Term Fire Behavior, NTFB models fire behavior using inputs for weather and wind that change over the duration of the simulation. Though NTFB can model fire growth for up to seven days, it is generally most appropriate for the 'near term' of one to three days (due to unknowns in the forecast beyond that time frame).
The model retrieves forecasted weather and winds for the selected time, using National Weather Service (NWS) Forecast Data for current simulations. For historic fires, the model can use historic weather.
The Fire Behavior Specialist can accept the fuel moisture, weather, and wind inputs, or can replace those values as needed. Within a short period of time (usually within a couple of minutes), WFDSS NTFB fire spread results are ready for viewing.
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Last updated on 6/25/2019 1:33:21 PM.
Recommendations for using NTFB
NTFB works a bit differently from the FARSITE that you are used to. FARSITE required a lot of time to build the data for the run, and consequently, was primarily used with medium, emerging incidents or established large fires. With NTFB, you can quickly produce model outputs for making decisions on new fires. However, if the fire is smaller than the resolution used by the model, you might see little or no fire spread (e.g., a 1/4-acre fire is smaller than a single cell on a 30-meter landscape). While these minimal model outputs could be realistic since live fire does require some momentum and time before it spreads, they often under-predict the fire growth. The modeled world is more homogenous than the real world so, if the growth of very small fires is being underpredicted by NTFB, it may be necessary to increase the fire size and capture a few more cells to represent the diversity in the fuels.
To get more realistic outputs, consider increasing the size of your ignition to at least 8 landscape cells (about 2 acres with a 30-meter landscape or around 7 acres at 60 meters) under the following conditions:
- for modeling 'worst-case' scenarios
- to account for local experience that indicates the model is under-predicting fire growth.
While 8 cells might be larger than your actual ignition, the effect of using a larger ignition size washes out over the course of the run and might return more realistic outputs.
In addition, it is important to remember that NTFB does not account for suppression action, an assumption that is particularly important when interpreting NTFB outputs for small fires.
CAUTION: Changing the analysis date, RAWS station, or burn period information, automatically repopulates the hourly records and overwrites your changes.
To run a NTFB:
- From the Incident list, select the incident for which you want to run NTFB.
- Click View Analyses. The Analysis List appears for the selected incident.
- Under New Analysis, select Near-Term, then click Create Analysis for Incident. The New Near-Term Analysis page appears.
- Enter an Analysis Name. 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.
Since incidents can have many analyses associated with them, be specific in your name (up to 48 characters).
- Set the conditioning days, spotting probability, and crown fire method. There is generally no need to change the spotting seed.
- Set the spot ignition delay and foliar moisture content.
- Set the start and end dates.
- For dates in the future, WFDSS uses forecast data.
- For dates in the past, WFDSS uses historic RAWS data.
- Upload ignition and barriers shapefiles. An ignition file is required; barriers are optional. If no ignition file exists, you can create it later (See Creating an Analysis Ignition File).
- Verify the RAWS station information.
- Click Create. The Detailed Near-Term Fire Behavior page appears. You can modify any information that was added in steps 4 - 9 here.
- Verify the following items:
- burn periods (typically, analysts will shorten the burn duration from the default 24 hours to the timeframes of active burning)
- wind information
- initial fuel moistures (herbaceous and woody fuel moistures typically need adjustment)
- hourly records (wind and weather)
- Click Save after making edits and before leaving the Near-Term Information Page.
- Create a landscape file and edit it if necessary. (See Creating the Landscape File and Editing a Landscape File.)
- Use the Requirements fly-out menu on the right to ensure all required components are completed.
- Click Run Near-Term Fire Behavior.The analysis runs. Depending on the parameters you selected, the analysis could take several minutes to complete.
Depending on the landscape size and resolution, as well as the traffic on the server, the analysis could take several minutes to run. Refresh your browser to see the status change to Complete, then select the analysis and click View Results to see the analysis on the map view.
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Last updated on 6/25/2019 1:33:21 PM.
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