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.
We keep hearing that wildfire seasons are becoming longer. One way to verify this for a particular location is by analyzing times of the year that fires occur and the acres burned by date. But researchers have provided more information for the longer fire season discussion by studying weather across planet Earth. They used the data for a 34-year period, from 1979 to 2013, to calculate the U.S. Burning Index, the Canadian Fire Weather Index, and the Australian (or McArthur) Forest Fire Danger Index. They normalized the daily fire danger indices to a common scale and resampled to a common resolution.
What the researchers found was that fire seasons have lengthened across 29.6 million km2 (25.3%) of the Earth’s vegetated surface, resulting in an 18.7% increase in global mean fire season length. They also show a doubling (108.1% increase) of global burnable area affected by long fire seasons.
There were no significant trends in mean annual total precipitation or total precipitation affected area but they did observe a significant increase in mean annual rain-free days, where the mean number of dry days increased by 1.31 days per decade and the global area affected by anomalously dry years significantly increased by 1.6% per decade.
It can be a fool’s errand to attempt to predict the severity of a wildfire season. Using past weather data to predict the nature and number of future fires often fails.
But an article written by Ben Boettger for the Peninsula Clarion is more intelligent than most about discussing what affects a fire season and what this one might look like.
Below are some excerpts from his article:
…[Meteorologist Sharon Alden of the Alaska Fire Service’s predictive office] said there is not a correlation between a warm winter and a busy fire season, nor a correlation between a less-snowy winter and a busy fire season.
“However, there is a correlation between snowpack and the early fire season—how fast things melt out, how soon fire season starts,” Alden said.
Alden said that the intensity of fire season is more tied to precipitation than temperature, leading Fire Services to begin early preparation during the critical months of spring.
“In early spring, before green-up, the forest fuels are dryer,” Alden said. “When you have green-up, when you have trees fleshing out and new green grass is growing, you have more moisture around and it becomes a little less receptive to getting a fire started.”
In addition to leaving less moisture on the ground, a lack of snow contributes to an early fire season through its effect on grass, since grass crushed down by snow burns less easily than standing grass. Kristi Bulock, fire management officer for the US Fish and Wildlife Service region that includes the Kenai Wildlife Refuge, said that the locally-abundant calamogrostis grass is a particularly good wildfire fuel.
“One of the concerns we have this year is that without the snowpack, the grass is still three feet tall,” Bulock said. “It’s up and it’s fluffy, and it’s available for burning, where generally, under a good snowpack, it would be matted down. And then as we start getting green-up we would start getting green shoots in between, and that would lessen the potential for that fuel to carry fire. But if you look out your window now you see these giant patches of cured grass… if we have any kind of ignition source — a cigarette, somebody dragging a chain on the road — the potential could be there for it to really move through that grass…”
On March 8 we looked back at the weather in the United States over the last three months knowing that it could have an effect on wildfires over the next three to six months. However the extent to which past weather influences future fires is debatable and can be overridden by the weather conditions during the fire season.
What is YOUR prediction for the 2015 fire season? Like the first robin you see in the spring, the assignment of the first Type 1 Incident Management Team (IMT) is a sign that things are getting real. In the last few years there have been about 30 to 50 assignments each year for T1 IMTs.
So let’s have a contest about the date the first Type 1 IMT will be assigned on a fire.
How to enter: In a comment below this article give us your prediction of the date the first Type 1 IMT will be assigned to a fire in 2015. In case more than one person selects the correct date, include the state. A second tie breaker will be the general area within that state. The date is defined by the date they are actually dispatched to a fire, not necessarily arriving at the fire. For the purposes of this contest, a Type 1 IMT includes only the 16 national interagency IMTs listed here. Only one entry per person, of course.
Deadline for entries: write your date with the two tie breakers in a comment below this article before April 1, 2015. If an IMT is assigned before April 1, the deadline for entries will change retroactively to the day before that fire started.
Prize: the winner will receive a limited edition Wildfire Today cap. So that we can contact the winner, you must enter your correct email address in the form when you are writing your comment. As usual, email addresses will never be disclosed to anyone without your specific permission.
Thanks and a tip of the hat for the idea go out to Dick.
The High Country News has an interesting article about the lengthening of the wildfire seasons. Below is an excerpt:
…For local residents, [the 7,000-acre Round Fire north of Bishop, CA on February 10, 2015] drove home a message Westerners may finally have to get used to: Fire season isn’t just confined to the months of July and August anymore, or even May through September. Over the last four decades, the season across the West has gotten two and a half months longer. Last year, rare January fires swept across southern California. And just last week, the Round Fire wasn’t the only abnormally early burn to hit the West. A spate of wildfires broke out in northern Utah Feb. 8 and 9, burning a few hundred acres.
These early season fires owe much to the ongoing drought. The area burned by the Round Fire is usually covered in snow at this time of year, but [local photographer Jim] Stimson said the ground is bare. California’s paltry snowpack, dry soils and unseasonably warm temperatures make it easier for a spark, whether caused by humans or lightning, to catch and travel faster and farther than usual. While it’s nearly impossible to pin any particular fire event to climate change, we do know that the changing climate exacerbates the drought, which leads to more fires. Scientists say that Westerners can almost certainly expect more early-season fires like the Round, as climate change continues…