Drought comparison

Comparing the latest drought monitor to the same time last year shows widespread improvement in drought conditions in Arizona. Currently, 17 percent of the state is in drought. Last year, 100 percent was in drought.

No more drought.

A wonderfully wet winter.

Heck — they’re still skiing at Snow Bowl in Flagstaff.

Joy. Joy. Joy. Who’s afraid of wildfire now? Bonfires and marshmallows for everybody!

Well, actually — hang on.

For starters, the National Weather Service predicts a “normal” fire season starting in May and running on into July, when the monsoon usually brings relief.

Granted, that’s way, way, way better than last year — when “exceptional” drought gripped the entire West and fuel moisture levels hit the lowest levels ever measured in many areas.

However, those winter rains fueled the growth of lots of grass and “fine fuels” — especially at lower elevations. So even if we do get the predicted wetter than normal May, we still have June — the hottest, driest month of the year.

“Current weather outlooks and ground conditions indicate a trend toward near normal fire potential this season across most of northern Arizona. Above normal fire threats at lower elevations due to abundance of fine fuels. At high elevations — possible delayed threat due to the wet winter,” the Weather Service said in its just-issued fire outlook.

But wait. It gets worse.

The once-reliable connection between a wet winter and a moderate fire season may not hold any longer, according to a study by researchers from the University of Arizona and elsewhere, funded by the U.S. National Science Foundation and the U.S. Geological Survey.

A century of fire suppression has built up so much fuel in the forest that the hot dry months can spawn a catastrophic blaze even after a wet winter, concluded associate professor of dendrochronology Valerie Trouet, a study co-author.

The study focused on the link between winter rain and snow and the subsequent wildfire season going all the way back to 1600. The northern jet stream generally controls winter precipitation. From 1600 to 1903, wet winters almost always produced a mild wildfire season, according to the study published in the Proceedings of the National Academy of Sciences.

After 1904, the connection began to weaken. That’s about when the Forest Service instituted a national effort to stamp out forest fires within a day, preventing them from growing into larger fires. The effort worked brilliantly for more than half a century, as the size of wildfires plunged. However, despite large-scale logging throughout the West, the timber harvest never came close to removing as much biomass as the previous pattern of frequent, low-intensity wildfires. Most of the fuel that accumulated wouldn’t have made any money for loggers anyway.

As a result, the density of trees in the forest increased dramatically. In Arizona’s ponderosa pine forests, the densities rose from perhaps 50 trees per acre to more like 600 to 1,000 trees per acre. In addition, the amount of debris on the ground rose dramatically.

The connection between wet winters and a cool fire season in California evaporated entirely after 1977, according to the study. Partly, that reflected the buildup of fuels in the forest. Partly, it reflected a warming trend in recent decades.

“The moisture availability over California is still strongly linked to the position of the jet stream, but fire no longer is,” said Trouet. “I didn’t expect there to be no relationship between jet stream dynamics and fire in the 20th century. I expected it to be maybe weaker than before, but not to completely disappear,”

For instance, in 2016-17 a wet winter yielded the Tubbs fire in October and the Thomas fire in December. Those fires killed 24 people and consumed almost 7,000 structures.

Trouet worked with scientists from a variety of other institutions to look at the connection between the jet stream, winter precipitation and wildfire, based on tree rings, historical records, and archives of climate and fire. National Oceanic and Atmospheric Administration scientist Eugene Wahl was the lead author. Trouet had previously reconstructed the patterns in the jet stream while co-author Alan Taylor had reconstructed wildfire patterns going back for 400 years.

The research suggests Arizona residents can’t afford to let their guard down after a wet winter in the new era of megafires.

The National Weather Service concluded the “odds are tilted in favor” of a wetter than normal May — normally the second driest month of the year.

June and July should be “normal” when it comes to rainfall — for the first time in years, although temperatures may be above normal.

The fire outlook maps show the southern half of the state will face an “above normal” fire risk, thanks in large measure to the growth of so much grass and other fine fuels. Rim Country falls right on the dividing line between “above normal” and “normal” fire danger.

Still, the wet winter made a tremendous difference — especially in the higher elevations of Arizona. Last year, Gila County had about 25-50 percent of the normal rainfall in the first three months of the year. But so far this year, we’ve received about 130-150 percent of our normal rainfall in the same period.

The Snow Bowl ski resort on Mount Humphrey this last week promised to stay open until at least the weekend of May 19, the longest season in its history. The previous record was held by the 2016-17 season. The resort still has a base of 68 inches, after having received 332 inches of snow in the course of the season. That’s the second highest snowfall total in the 25 years of record-keeping.

Meanwhile, Roosevelt Lake has risen to 76 percent full, with the other Salt River reservoirs full almost to the trim.

The six lakes Salt River Project operates on the Salt and Verde rivers stand at about 81 percent full, compared to just 58 percent at the same time a year ago.

The Salt River continues to gush with runoff from the White Mountains, running at 1,500 cubic feet per second — about 151 percent of normal. The Verde River — at 172 cfs — and Tonto Creek — at 30 cfs — are running at just a little bit below normal.

Contact the writer at paleshire@payson.com

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