Predicted Rainfall Could Mean an End to Oklahoma Wildfire SeasonMon, 11 Apr 2016 17:17:01 CDT
Oklahoma sometimes receives a lot of moisture from El Nino during the winter and spring seasons, but that is not the case so far in 2016. Rather, the state has experienced very limited rainfall, as there has been a dominant ridge of high pressure over the western United States.
Statewide, Oklahoma is approaching the 20th driest start to a calendar year since at least 1921.
“The earlier prediction that the ongoing strong El Nino might result in lower wildfire activity during our dormant season in Oklahoma has certainly not materialized,” said J.D. Carlson, Oklahoma State University fire meteorologist. “While the last two months of 2015 resulted in above normal precipitation for Oklahoma, since the start of 2016, the spigot has pretty much turned off and 31 percent of the state is now in moderate drought, largely in the panhandle and northwest Oklahoma.”
In addition, the dry air and frequent strong winds have resulted in an active fire season, especially over the past month.
The Anderson Creek megafire in late March, which is the largest wildfire in Kansas history, burned almost 368,000 acres in Woods County, Oklahoma, and Comanche and Barber counties in Kansas. The current 350 Complex fire northeast of Woodward, Oklahoma, has burned over 57,000 acres at the time of this writing.
“Complicating the picture are the excessive fuel loads compared to normal, especially in northwest Oklahoma, caused by the much above-average rainfall during spring 2015,” Carlson said. “In addition, due to the lack of precipitation thus far in 2016, areas such as northwest Oklahoma have not greened up yet.”
The lack of green-up in the northern parts of the state has kept most of the available fuel as dead fuel, such as dormant grasses, that can easily burn once relative humidity drops and winds pick up.
Normally wildfire activity drops dramatically in Oklahoma in May, but what about the rest of April?
“There are reasons for optimism, as a major change in the jet stream pattern will soon materialize,” Carlson said. “Instead of the heretofore dominant northwest flow over Oklahoma, we are anticipating strong upper-level westerly flow off the Pacific with periodic storm systems moving across Oklahoma through most of the rest of April.”
These storms should not only boost rainfall amounts, but also lead to more hours of high relative humidity, both of which serve to inhibit wildfire initiation and growth. According to the latest Global Forecast System numerical weather model, much of the state is expected to receive several inches of rain through April 23.
The latest 6-10 day and 8-14 day precipitation outlooks are consistent with this, indicating increased chances for above normal rainfall for Oklahoma, especially in the western sections.
“Perhaps more important than the rain itself, the moisture will accelerate green-up in areas that have yet to do so, which will further decrease fire danger in those areas,” said Carlson. “Of course, wildfires will still be possible in between storm systems during periods of low relative humidity and high winds, but increased rainfall, more periods of higher relative humidity and further green-up should cause a dramatic drop in wildfire activity in Oklahoma as we go through the rest of April.”
Wildland fire managers are encouraged to consult the OK-FIRE system (okfire.mesonet.org), which provides current and forecast fire weather and fire danger information up to three days in the future.
Souce - Oklahoma State University Agricultural Communications Services
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