Precipitation and radar reflectivity associated with natural wildfire ignitions in Arizona and New Mexico

Lightning is a predominant feature of convective weather environments of the Southwest U.S., and natural wildfires are often ignited by lightning strikes that reach the surface. However, lightning ignited wildfires account for less than 0.35% of all recorded cloud-to-ground lightning strikes that occurred during the fire season from 1990--1998, in Arizona and New Mexico. A major challenge for fire weather forecasters is to assess the potential for fire ignition in areas of lightning activity. Improving fire ignition potential forecasts can provide information for fire resource managers and planners. Fire management resources are shared throughout the country, so it is important to know in advance where these resources are needed most, should an outbreak of natural fires occur.; Precipitation associated with lightning can lower the potential of natural wildfires. This study employed daily and hourly gridded precipitation derived from historical gauge data to relate precipitation amounts to natural wildfire ignitions in various vegetation and elevation regimes. Relationships between gridded precipitation and natural wildfire ignitions can be applied to gridded forecasts of precipitation.; Atmospheric moisture pulses associated with the North American Monsoon provide much needed precipitation to raise the moisture content of fuels to a level for wildfire ignition prevention. This study examined the relationships between the timing of monsoonal precipitation and lightning pulses to the timing of natural wildfire ignitions. Knowing the number of days between the most recent precipitation pulse and when the next natural wildfire ignition occurred can assist in resource management and planning.; Radar reflectivity data was used to characterize radar echo characteristics associated with natural wildfire ignitions. Real-time radar reflectivity and lightning data can be examined for radar echo characteristics that were associated with natural ignitions in the past.; By analyzing gridded precipitation and weather radar reflectivity data with lightning and wildfire data, fire weather forecasters can identify regions of increased ignition potential. The results of this type of analysis can help focus attention of wildfire personnel to particular locations where there is known to be cloud-to-ground lightning in conjunction with low amounts of precipitation and radar reflectivity patterns that are associated with wildfire ignition.