How Fire Weather Forecasts Assist Fire Fighters and the 2007 Fire Season
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 Okefenokee Swamp.

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 Florida and southeast Georgia.  Although fires can occur during warmer spells between winter frosts, fire intensity increases as temperatures warm in the spring.  Forestry officials will step up pre-suppression activities during the cooler months to minimize the fuel loading prior to the warmer part of fire season.

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 Florida, these conditions are based on relative humidity and winds only.  State and local officials are responsible for determining whether burning is safe or not.  These decisions are likely based on the weather information provided as well as condition of fuels and soil moisture.  As with other National Weather Service watches and warnings, a watch can be posted up to 72 hours in advance of the event and a warning is posted when the event is impending or occurring.

 The 2007 Fire Season

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 Waycross, Georgia.  Fires caused many roads to be closed and forced evacuations of thousands of people from their homes.  On May 8, lightning started the Bugaboo Scrub Fire in the Refuge.  This fire soon spread across the state line into Florida. Smoke from this complex of fires spread into Lake City causing hundreds of homes to be evacuated.  Dense smoke prompted highway officials to close a 40 mile stretch of Interstate 10, and a 35 mile stretch of Interstate 75 north of Lake City into Georgia.  On other days, southeast winds carried the smoke to the Atlanta area and northwest flow carried the smoke into Jacksonville.  Visibility was reduced to less than one half mile in mid day from the smoke.  Persons with respiratory problems found it necessary to stay indoors.  By the end of May, over 600,000 acres had burned, becoming the largest fire in history for this region.

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 Florida was also under siege from several wildland fires.  Although residents of Flagler county had practiced the drill in 1998, this time they did not have to evacuate the county.  Fires raged between Hampton and Keystone Heights forcing evacuation, road closures and destroying one home.

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 Jacksonville sojourned to the Ware county EOC in Waycross to give daily briefings on weather conditions and the ongoing drought.