10, 000, 000 



LENGTH/ WIDTH RATIO 

 Figure 8.— Fire size and sliape changes during 

 the history of obsenred fires. 



Example Fires with the Critical Values Tabulated 

 Example 1: 



Air Force Bomb Range Fire on March 22, 1971 (Wade and 

 Ward 1973) started at 1028 and began crowning about 1230. 

 This continued until 1745, after which the fire encountered 

 wet fuel and wind changes occurred with fronts moving 

 through the area. Wind direction changes complicate use of 

 the ellipse model and make results more uncertain. Notice 

 that the wind acting on the flame to match observations 

 was to reduce the 20 ft (6. 1 m) wind to 9.4 mi/h (15.0km/h) 

 for the fire burning in grass and low shrubs. After 1230 the 

 observed wind was only reduced to 15 mi/h (24.0 km) because 

 the fire was carried in the crown of the pond pine {Pinus 

 serotina Michx.) plantation. The fit of the adjusted double 

 ellipse is shown in figure 9. 



Example 1. The Air Force Bomb Range Fire in Florida started in brush ana 

 grassy fuels and about 2 hours later started crowning in pine plantations 

 (P. serotina). Fire start was 1028 on March 22, 1971. 



Variable Documented Simple ellipse Double ellipse Double ellipse 

 values values values adj. values 



Time 1100.0 hours 



Area 



8.0 acres 



8 



5.6 



3 



pertmeier 



.5 miles 



5 



.o 



c 



Distance 



.2 miles 



.2 



.2 



.2 



Windspeed 



W 20.0 mi/h 





12.2 



9.4 



//w 



3:1 



3.2:1 



4:1 



3:1 



Time 



1226 









Area 



155 



155 



102 



159 



Perimeter 



2.1 



2.1 



2.0 



2.2 



Distance 



.9 



.9 



.9 



.9 



Windspeed 



WSW 20 





13.0 



9.5 



ll\N 



3.1:1 



2.8:1 



4.3:1 



3:1 



Time 



1439 









Area 



2,094 



2,094 



2,845 



2,099 



Perimeter 



10.2 



10.2 



10.3 



9.9 



Distance 



4.6 



4.6 



4.9 



4.6 



Windspeed 



SW 15 





12.5 



15.0 





5.4:1 



5.8:1 



3.5:1 



5.4:1 



Time 



1537 









Area 



2,975 



2,975 



4,589 



2,982 



Perimeter 



11.6 



11.6 



12.3 



11.5 



Distance 



5.3 



5.6 



5.3 



5.3 



Windspeed 



SW 15 





10.9 



14.4 





5.3:1 



5.2:1 



3.5:1 



5.1:1 



Time 



1636 









Area 



6,518 



6,518 



6,297 



6,485 



Perimeter 



20.5 



20.5 



20.8 



20.9 



Distance 



10.1 



10.1 



10.1 



10.1 



Windspeed 



SSW 20 





19.0 



18.8 



f/w 



8.1:1 



7.8:1 



8.4:1 



8.2:1 



Time 



1745 









Area 



9,796 



9,796 



12,434 



9,819 



Perimeter 



29.1 



29.1 



25.6 



25.1 



Distance 



12.1 



14.4 



12.1 



12.1 



Windspeed 



SW 20 





16.3 



18.3 



//w 



7.8:1 



10.7:1 



6.2:1 



7.8:1 



9 



