How Fire Weather Forecasts Assist Fire Fighters and the 2007 Fire Season by Marie Trabert, Fire Weather Program Leader
by Marie Trabert, Fire Weather Program Leader
Weather patterns can have a profound influence on fire activity. Long term drought is an obvious factor, but any weather pattern that promotes drying of fuels or entrapment of smoke can be a serious concern to fire fighters.
The passage of dry cold fronts with strong shifting winds will cause erratic fire behavior. Smoke impacts may be high following a weak cold front where wind speeds are lower, since a cold and stable air mass can pose a problem by trapping smoke near the ground. As a stationary front meanders over a region, it can result in variable transport winds that have no sustained or predictable direction. Upper level winds in the atmosphere moving in a different direction than surface winds can be responsible for transporting smoke hundreds of miles downstream as occurred in the 2007 fires near the
Stationary high pressure systems with prolonged subsidence can dry fuels. When this occurs during late spring then above normal temperatures will increase fire behavior.
During summer months, which is typically the wet season, sea breezes or winds from thunderstorm outflow can cause erratic fire behavior. Occasionally, lightning strikes will start wildfires as was the case in the devastating 1998 fire season.
We are now entering the height of fire season, which generally runs from late January through May in north
Fire Weather Forecasts
Each National Weather Service office issues daily fire weather forecasts for the purpose of assisting federal, state and local land managers in planning activities, or allocating resources. Forestry officials and fire management supervisors will make decisions based on the forecasted weather conditions. Fire weather forecasts contain special elements that are important to wildland fire managers, such as, mixing height, transport winds, lightning activity level (LAL), dispersion index and LVORI.
Mixing height refers to the height of vertical mixing of air, often below the base of an inversion, and typically much higher in the warmer summer months. The transport winds are the average winds within the mixed layer. The dispersion index not only provides guidance on whether smoke will disperse or hover near the ground, but also indications of erratic fire behavior. LVORI (Low Visibility Occurrence Risk Index) is an indicator of when smoke or fog can pose a risk of settling on the ground at night.
Red flag warnings and fire weather watches are special products designed to alert fire management officers about weather conditions that could promote dangerous fire situations. In
Extreme drought conditions in 2007 combined with persistent dry fuels to cause the worst fire season seen locally since 1998 with the largest fires in and near the Okefenokee National Wildlife Refuge. The Sweat Farm Road Fire began April 16 when strong winds caused a tree to fall on a power line. Four days later the fire entered the Okefenokee NWR and was bearing down on
This picture of the smoke plume from the Bugaboo Scrub Fire was taken by NASA’s Terra satellite. Remnants of a tropical storm did little to slow the fires.
In early May, northeast
On-Site Support Available
For large fires the National Resource Coordination System will send an Incident Team to the site to supervise placement of personnel and equipment, and to order resources including a meteorologist from the National Weather Service. This incident meteorologist or IMET will provide weather forecasts for the specific fire location as well as participate in shift briefings, planning and strategy meetings.
Prior to the arrival of the incident team in 2007, several meteorologists from the Weather Forecast Office in