|News - July 11, 2011|
While several fires burn throughout the state of New Mexico, one might wonder what is involved in forecasting fire weather, and where to find information about fire weather.
Wildfires need hot, dry and windy conditions to spread. Typically, wildfires are more common in the summer months before the monsoon season due to the dry conditions, as well as the fact that more people are camping, setting off fireworks and just generally outside in the woods. Furthermore, fires can be sparked by the lightning produced by the afternoon summer storms that often accompany summer weather or by high winds blowing over trees into power lines. The fire near Los Alamos this year is believed to have been started by a tree falling into power lines during high winds.
The Storm Prediction Center (SPC) in Norman, Oklahoma predicts when conditions will be right for wildfires, just as they do for severe thunderstorms. Each day, they compile a product known as the Fire Weather Outlook which shows the risks throughout the country. Their website is http://www.spc.noaa.gov
There are several products associated with the Fire Weather Outlook. There are the Day 1 and 2 Fire Weather Outlooks, a Day 3-8 Fire Weather Outlook, and Fire Weather Composite Maps which allow anyone to overlay different meteorological parameters over a map to help locate particular trouble spots. These tools are freely available on the SPC's website, though the Fire Weather Outlooks are of the most interest to the layman.
The Day 1 and Day 2 Fire Weather Outlooks display several types of threats: SEE TEXT, CRITICAL and EXTREME. A SEE TEXT threat means that there are some conditions which might lead to fire danger, but some pieces are missing; perhaps the humidity is low, but there is not much wind in the area. A SEE TEXT threat area means that conditions could change throughout the day, and the threat in this area might increase. A CRITICAL threat area is one where conditions are ripe for a wildfire, and an EXTREME threat area means that the smallest spark can cause a wildfire that will spread rapidly.
The Day 3-8 Fire Weather Outlook does not assign risk levels, but merely risk areas. It shows a map of the United States and areas where there will be some risk of wildfire on days 3-8. This map can reveal whether or not an area will be under a fire risk for a long time; each day that passes without rain increases the fire risk for the following day.
For those interested in the specifics of the current fire threat, the Fire Weather Composite Maps (often referred to as Comp Maps) are a good place to start. The user can pick a geographic region (NM is located in the "Southwest" Map), and begin overlaying relative humidity, wind speed and several other parameters on the map. These parameters are based on the NAM model, but they give the forecaster clues as to where a threat will likely occur. Below is an example of the Comp Map in action, with relative humidity and wind speed (the blue barbs) overlayed. Thankfully, the wind appears to have died down.
Overall, these fire weather tools are useful for determining a threat area. However, they cannot guarantee a fire will or will not occur. An area with high risk will not burn without an ignition source, and an area with no risk can quickly dry out if conditions are favorable.