Rainfall over the last two weeks has slowed or in some cases, ended the wildfire season in some areas.
On October 19 we ran the numbers for the accumulated precipitation for the last 14 days in the western states. These maps show amounts that exceeded 0.05 inches at some of the Interagency Remote Automatic Weather Stations (RAWS).
Washington, Oregon, and northern California have received a good soaking and I would imagine that local fire officials may be declaring an end to the fire season. Of course this is not unusual for these areas this time of the year, and some locations had already seen their season end. But what IS unusual, is the high amount of moisture that occurred in just two weeks.
You can click on the images to see larger versions.
On October 1 the Predictive Services section at the National Interagency Fire Center issued their Wildland Fire Potential Outlook for October through January. The data represents the cumulative forecasts of the ten Geographic Area Predictive Services Units and the National Predictive Services Unit.
If their predictions are correct, firefighters in the mountains of central and southern California could be busy through November, at least, while most of the Southeast is coming into what could be a very active fall fire season.
Scroll down to see 6 to 14-day temperature and precipitation outlooks, and Red Flag Warnings for October 2, but immediately below are highlights from the wildfire potential outlook.
“October represents a significant shift in fire activity in the United States. Shorter days, cooler nights and generally moister conditions reduce wildfire activity across the northern tier of the U.S., taking much of this area out of season or at least to very low fire activity conditions.
“October does represent the beginning of the primary time of concern for offshore flow across California. These dry windy conditions can lead to very significant fire events in areas with high populations. This year the forecasts indicate that offshore wind events may be less frequent than usual. However during even light wind periods fires will occur and they will have the potential to spread extremely quickly with extreme fire behavior. Fuels continue to be very dry in California due to long term drought and increased vegetation stress and mortality. Under windy conditions these fuels will become extremely volatile and can support extreme fire behavior.
“October also marks the start of the fall fire season across the eastern U.S. Leaf drop begins and adds a new dry layer of fuel. In seasons such as this one where leaf drop occurs on already dry fuels, fire activity can be amplified. Expect this to lead to increased initial attack activity and probably a slight increase in large fires. Fire activity occurs year round in the southeastern U.S. so the most likely scenario is to see an increase in frequency and the potential for more control problems than usual on fires this fall.
The National Fire Danger Rating System tracks weather events through their effects on live and dead fuels and adjusts them accordingly based on forecasted weather. The most visible product of the system, which is used by most large land management agencies in the United States, is the predicted fire danger, often expressed as adjectives ranging from Low to Extreme.
The NFDRS was first released for general use in 1972 and was subsequently revised in 1978 and 1988. Work on another revision began in 2000 and is nearing completion. Reportedly this next version is much simpler and more automated than its predecessors and it represents a vast improvement in fire potential assessment capabilities.
Three major changes will be:
The Fosberg Dead Fuel Moisture Model will be replaced with the Nelson Dead Fuel Moisture Model.
The Burgan Live Fuel Moisture Model will be replaced with the Growing Season Index-based live fuel moistures.
The number of fuel models in the NFDRS will be reduced from 40 to 5.
Jon Wallace, a member of the team rolling out and implementing the new system described the transition in an email today:
“The system is expected to be back from contracting and thus complete on November 1st of 2016. After the first of the year we’re going to begin training of Subject Matter Expert groups located within each geographic area, and when that training is complete we will open the system up for all users. We had to wait to conduct this training until the system was fully functional.
“As you can imagine, there is going to be a learning curve for the user community and these Subject Matter Expert groups are going to help us get through that curve within their respective geographic area.
“All members of the user community will be able to see the new NFDRS2016, as well as the 1978 and 1988 NFDRS models during the spring of 2017. This will allow them to work with the subject matter expert groups to set up NFDRS parameters prior to the Summer of 2017 fire season. They will then be able to compare the outputs of the new system to what they are used to seeing in the older versions of NFDRS.
“This side by side comparison will be available to users through the 2018 fire season, at which time we will re-evaluate the need to continue support of the old systems.”
This is a rather surprising 2-minute video about attributing wildfires to climate change. It was produced by the National Center for Atmospheric Research and the University Corporation for Atmospheric Research.
Friday’s weather includes Red Flag Warnings in the west and a hurricane on the east coast
Above: Weather forecast, current at 9 a.m. MDT September 2, 2016. Weatherunderground. Black text added by WildfireToday.
The weather map for the United States today has quite a range of conditions across the country. While Hurricane Hermine, now downgraded to a tropical storm, batters the southeast, a cold front is bringing strong winds and low humidities to some areas in the west. There is a chance of isolated dry thunderstorms in northwest Wyoming and eastern Montana.
On September 1 the Predictive Services section at the National Interagency Fire Center issued their Wildland Fire Potential Outlook for September through December, 2016. The data represents the cumulative forecasts of the ten Geographic Area Predictive Services Units and the National Predictive Services Unit. Below are highlights from the outlook.
September is typically a month of significant change in fire conditions, especially across the northern tier of the United States. Days shorten, lessening available solar radiation to dry and heat fuels; longer nights are cooler with generally higher humidity. These conditions slowly reduce fire activity and typically end normal fire season activity throughout the month. This is expected to be the trend this season as well.
Throughout the northern portions of the Great Basin including portions of the Northwest, Northern Rockies and Rocky Mountain Areas above normal conditions will transition through the month to normal conditions and by the end of September normal conditions indicate minimal fire activity throughout this area. Occasional dry cold fronts during September and possibly October will present the potential for large fires on the landscape to grow rapidly; however, these conditions will be short in duration followed by opportunities for successful firefighting efforts. California will remain at above normal levels of fire activity throughout much of the state as dry conditions will continue and fall will bring the increased potential for offshore flow events.
In October, November and December diminishing activity in the northern tier will transition to heightened activity across the southern tier; especially in central and southernCalifornia and the Southeast. California is not expected to see any significant events that will alleviate long term drought and very dry fuels. This will come with enhanced potential for offshore flow, increasing the potential for very dry and windy conditions. The southeastern United States is a significant wildcard moving into the fall months.
Tropical systems the Atlantic Ocean and Gulf of Mexico could provide substantial relief to some if not all of the area.
If this dry area remains, fall fire activity in the Southeast will be amplified and could become significant throughout the fall and winter. It is possible significant changes will occur, but the current conditions dictate elevated potential is likely.