Meteorologist at Weather Underground, background in fire weather research. Twitter: @WunderKari
By: Kari Kiefer , 9:46 PM GMT on June 01, 2011
It's about time to get back into blogging, especially with all these fires across the South! As you may have noticed, my last blog was during my thesis research on smoke plume dynamics. A few students and my adviser took a trip to rural Georgia to take measurements during prescribed fires. We took two trips for seasonal comparison: July 2008 and January 2009. It was interesting to see how the drier winter fuels affected the plume dynamics, compared to that of the moist summer conditions. I will be happy to share some of my findings as we move through this fire season.
But for now, lets start with some basic FAQ:
What is a Red Flag Warning?
As defined by the NWS:
Red Flag Warning
A term used by fire-weather forecasters to call attention to limited weather conditions of particular importance that may result in extreme burning conditions. It is issued when it is an on-going event or the fire weather forecaster has a high degree of confidence that Red Flag criteria will occur within 24 hours of issuance. Red Flag criteria occurs whenever a geographical area has been in a dry spell for a week or two, or for a shorter period , if before spring green-up or after fall color, and the National Fire Danger Rating System (NFDRS) is high to extreme and the following forecast weather parameters are forecasted to be met:
1) a sustained wind average 15 mph or greater
2) relative humidity less than or equal to 25 percent and
3) a temperature of greater than 75 degrees F.
In some states, dry lightning and unstable air are criteria. A Fire Weather Watch may be issued prior to the Red Flag Warning.
Why do we need fire these warnings? (Crazy, I know, but I've been asked this!)
Wildfires can start just on the outside of towns. Depending on the wind strength and direction, fires may rapidly move toward homes and communities, putting many people in danger. Especially in southern California, wildfires have caused billions of dollars in damage and ruined many large and expensive homes. Red flag warnings alert these communities to get out of danger's way!
Where do we find information on current or active fires?
TheWundermaps Fire Layer is a great source for today's active fires. These are MODIS satellite detected fires. The caution icons portray the named fires, as they have become large and dangerous by the USDA Forest Service. They define large fires as "A wildfire of 100 acres or more occurring in timber, or a wildfire of 300 acres or more occurring in grass/sage." This map also shows the smoke plume and areas that may be of risk for poor air quality from smoke. Additionally, you can change the date to look at active fires for the past 7 days.
The USDA also has a nice map of the Current Large Incidents.
Figure 1. USDA Current Large Incidents for June 1st, 2011. Named large active fires across the US for Wildland fire; Type 1 Incident Management Team Assigned (red circle), Wildland fire; Type 2 Incident Management Team Assigned (blue circle), Wildland fire; Other Incident Management Team Assigned besides a Type 1 or Type 2 team (e.g. Type 3) (green circle), and Any nonstructure fire, other than prescribed fire, that occurs in the wildland (purple circle).
What are favorable conditions for fire ignition and fire spread?
WARM, DRY, AND WINDY! The less obvious factors are a result of these three components. When environmental conditions are dry, the fuel moisture drops. Fuel moisture is the amount of moisture in the grass, shrubs, or trees of which the fire consumes, hence, fuel. A major branch of Fire Science looks into the critical moisture levels for various types of vegetation. The USDA Landcover map is helpful when fires are a threat. Mixing height, Lightning Ignition Efficiency, and the Haine Index are additional things to check when looking at fire probability. But we will dive into these topics later...
Figure 2. USDA Land Cover for June 1st, 2011. Various vegetation types ranging from Evergreen Needleleaf Forest (green) to Cropland (brown), and Urban (pink). Please see the link for the full list of vegetation types.
Where can I find forecast fire weather information?
Also on the USDA Forest Service site, is a Forecasted Fire Danger map. As you can see on the below image, the highest risk for fires is currently across the High Plains of Colorado, New Mexico, and the panhandle of Texas. Very high and extreme risk is also scattered from Southern California to New Mexico.
Figure 3. USDA Forecasted Fire Danger. Low (green), moderate (lime green), high (yellow), very high (orange), and extreme (red).
Also pay attention to the Red Flag warnings from the NWS that you can see on the Severe Layer of Wundermaps.
Figure 4. The non-Wundermaps version of US Severe Alerts map. Fire weather advisories are show in Orange.
Lastly, I found this cool map for 7 day forecast of Significant Fire Potential. The site lets you scroll through the seven day forecast, but this is a nice quick-view composite of the images.
I realize this is a lot to absorb! I will update more next week with information on current fires across the US. Please post any questions you may have on Fire Weather and I will try to answer them as best I can!
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.