Afternoon Fuel Model Break and Spotting
You are an FFT2 assigned to a 20-person initial attack crew on a fire that started in cheatgrass at the base of a north-facing slope. At 1300 the fire is 5 acres, wind is 8 mph from the west, relative humidity 35%, and temperature is 88°F. The lower slope is fuel model 5 grass; above it the fuel changes to fuel model 10 timber litter with a closed canopy. By 1500 the fire is 60 acres, wind is 15 mph gusting 25, relative humidity 22%, and temperature is 95°F. You see short-range spotting 200 yards ahead, a column leaning downwind, and the fire backing into a gully with unburned fuel above. The division supervisor asks whether to keep the crew on the direct flank or move to a road on the ridge. Your crew has one sawyer, six hand-tool firefighters, and a Type 6 engine with 300 gallons.
1. Identify the fire behavior indicators and explain how the fuel model change affects probable spread and control options.
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Indicators: RH falling from 35% to 22%, temperature rising to 95°F, wind increasing and gusting, short-range spotting, column leaning downwind, and fire backing into a gully with unburned fuel above. These point to increasing probability of ignition and faster spread. Fuel model 5 grass is fine, cured, and fast-burning; it responds quickly to wind and can carry fire rapidly, but flame residence is short and direct attack can work if anchored. Fuel model 10 timber litter is heavier, with more fuel loading and longer residence; it produces more intense heat, torching, and lofted embers, and it will hold heat in mop-up. The transition from grass to timber litter is a fuel model break. Expect the fire to slow in grass but intensify and spot when it enters the timber. Control options shrink because direct flanking above the break exposes crews to torching and spotting over the line.
2. Recommend direct or indirect tactics and state trigger points for disengagement.
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I would move the crew off the direct flank and use the ridge road as an anchor and holding feature. The direct flank is above a gully with unburned fuel, and spotting is already 200 yards; a crew there can be outflanked. The road gives a defensible line, access, and a clear escape route. Use indirect tactics only if you have qualified supervision and can burn out safely; otherwise hold the road, protect values at risk, and order additional resources. Trigger points for disengagement: sustained wind above 20 mph, spotting more than 50-100 yards ahead, fire crossing the gully, column becoming vertical or collapsing, RH below 20%, or crew working more than 30 minutes without re-establishing LCES. If any trigger is met, stop line construction and move to the road or black. Report the trigger to the division supervisor.
3. What weather observation would most change your forecast, and how would you report it?
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The observation that would most change the forecast is a wind shift or an increase in gust spread, because it would change the direction of spread and the safety of the road. A second would be RH recovery after sunset, which could slow spread. Report using time, location, elevation, fuel, temperature, RH, wind speed and direction, cloud cover, and fire behavior: for example, '1500, lower slope, fuel model 5/10 break, temp 95, RH 22, wind west 15 gusting 25, spotting 200 yards, column leaning downwind.' Add what changed since the last report. Send to dispatch and division, and request the report be passed to the fire behavior analyst if assigned. Document the report.