On the morning of June 26, after a change 

 from steady, light northeasterly wind to a vari- 

 able wind, and under moderate fire-weather and 

 clear-sky conditions, the fire began crowning at 

 80 chains per hour up a 75-percent slope con- 

 taining black spruce. At 1000 all the weather 

 conditions worsened, many dust devils occurred, 

 cumulus clouds began to form, the smoke column 

 rose rapidly and high, but the fire slowed to 20 

 chains per hour on a 35-percent slope, still in 

 black spruce. The wind was now from the north 

 and continued there all day. The fire continued 

 to advance but not with extreme behavior char- 

 acteristics. 



At 1600, however, to quote the fire-be- 

 havior report, "A whole north-south wall of flame 

 is moving west over a ridge at a fantastic rate 

 — possibly a good 5 miles per hour. No warn- 

 ing — the whole V 2 mile of flame started within 

 3 minutes." The smoke column continued to rise 

 for some distance, then toadstooled. There had 

 been no noticeable weather, fuel, or topographic 

 change (21- to 50-percent slope) to cause this 

 erratic behavior,- however, the 1800 observation 

 mentions fully mature thunderheads with virga 

 in the vicinity. Maximum wind velocity at the 

 weather station, though, was only 1 1 miles per 

 hour. At 1930 the wind shifted from north to 

 southeast, the fire subsided and remained quiet 

 during the night. The fire was now about 13,000 

 acres in size. 



Since the available firefighting crew was 

 so small and the extended period of fire weather 

 was so adverse, the fire was finally abandoned 

 in late evening on July 1. More complete 

 weather observations and intensive study of the 

 atmospheric conditions might have led to a 

 better explanation of the fire's rapid spread. 



SUMMARY 



Topography to windward of the Healy fire 

 fo rms a saddle through which wind velocities 

 are usually greatly increased. This fact is the 

 major reason for the fast spread and difficult 

 control of the fire. 



The broken topographic complex on the lee 

 side of a broad flat valley, high burning index, 

 thunderstorms, and instability all contributed to 

 the irregular and difficult time for predicting be- 

 ha vior of tne Murphy Dome fire. One day the 



fire spread for several hours at a rate of 40 

 chains per hour. 



Topography surrounding the Kenai Lake fire 

 vicinity is extremely rugged and consists, in part, 

 of steep canyons converging on the upper end 

 of the lake. The resultant strong diurnal winds 

 reverse their direction in morning and evening; 

 altered atmospheric conditions also violently af- 

 fect the wind pattern. The diurnal effect caused 

 serious trouble on one day, and a front moving 

 through caused considerable loss of line on an- 

 other day. 



The worst fire weather of all the fires re- 

 ported here occurred on the Colorado Creek fire. 

 The brisk winds that were altered by steep to- 

 pography, highly flammable fuels, and generally 

 critical fire weather all contributed to the dif- 

 ficulty of predicting fire behavior and taking ap- 

 propriate control measures. A spread of 140 

 chains per hour in black spruce was recorded 

 for a brief period. 



The initial run of the Lake 606 fire was 

 caused by strong winds. The greatest spread, 

 however, was apparently caused by thunder- 

 storm downdrafts and unstable atmospheric con- 

 ditions. 



Constant rapid spread of the Stony River fire 

 was aided by unbroken horizontal fuel continuity 

 and relatively unstable air associated with a 

 frontal activity which changed the wind direction 

 a total of 270 degrees. The fire traveled at a 

 rate of 33 chains per hour at times. 



Thunderstorm downdrafts may have caused 

 a y 2 -mile section of the Huggins Island W-10 

 fire to advance briefly at a rate of 320 to 400 

 chains per hour. A local wind-topography-black 

 spruce fuel situation may have caused another 

 rapid advance of 45 to 90 chains per hour. A 

 wind switch accompanied by local instability 

 accounted for still another advance rate of 80 

 chains per hour. Rough topography, variable and 

 gusty surface winds, evidence of high winds 

 aloft, and local atmospheric instability all con- 

 tributed to periods of extreme fire behavior. 



From these case histories very few specific 

 conclusions can be drawn. However, for the 

 first time some systematic measure was made of 

 the weather, topography, and fuel conditions 

 during actual free-burning periods of wild fires 



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