RESEARCH SUMMARY 



THE AUTHOR 



Research findings support the contention that the 

 well-documented increase of windspeed on high mountain 

 slopes at night is due to the occurrence of a low-level jet 

 wind. Various aspects of the meteorological situation most 

 likely to produce these nocturnal mountain winds are 

 discussed. An established jet-wind theory (Blackadar 

 1957) can be used to predict the strength of these mountain 

 winds during the course of an entire night. An example is 

 given of a low-level jet wind that produced strong winds 

 on a ridgetop fire at night. 



The purpose of this report is to explain the windspeed 

 increase on mountain slopes at night. Additional work is 

 required to determine such things as the frequency of the 

 winds, the area affected, seasonal variation, and the 

 effect on fire behavior. Also, additional studies are 

 needed to develop the type of procedures required to 

 forecast these nocturnal mountain winds. 



ROBERT G. BAUGHMAN was introduced to meteorology 

 while serving as an air-crewman with the U.S. Navy Air 

 Corps during World War II. He later received degrees 

 in meteorology and climatology from the University 

 of Washington (B.S. 1954, M.S. 1957). During the 

 period of 1954 through 1958, he was engaged in arctic 

 and cold regions research while with the U.S. Army 

 Corps of Engineers. In 1958, Baughman joined the 

 USDA Forest Service as a research meteorologist, with 

 responsibility for research on fire-setting lightning 

 storms, weather modification, and forest meteorology. 

 Currently he is a member of the Fire Behavior research 

 work unit at the Northern Forest Fire Laboratory in 

 Missoula, Mont. 



CONTENTS 



Page 



INTRODUCTION 1 



BACKGROUND INFORMATION 2 



BLACKADAR JET-WIND THEORY 2 



SYNOPTIC CONSIDERATIONS OF THE 



LOW-LEVEL JET 3 



REPORTED JET-WIND OBSERVATIONS 3 



SUNDANCE FIRE - LOW-LEVEL JET 4 



SUMMARY 5 



PUBLICATIONS CITED 5 



