El Niño delivered after all.
At least, for the moment.
Rim Country residents spent a sunny Sunday and Monday digging out from a storm that filled reservoirs to overflowing and dumped almost as much rain on Payson in five days as we received all of last year — all in the shadow of forecasts that call for new, weaker storms on Wednesday and again on the weekend.
National Weather Service forecasters said the near-record storm followed patterns typical of a strong El Niño year — but they don’t know whether it will last.
“Generally these patterns come in waves,” said Nick Petro, a National Weather Service meteorologist based in Flagstaff.
Payson got 9 to 11 inches of rain in five days, he said. Normally, Payson gets just over two inches of rain in January.
For all of last year, Payson got less than 11 inches — about half the normal annual average.
The chain of wet winter storms dumped 54 inches of snow on Flagstaff in five days, the third heaviest five-day accumulation since the start of record keeping there.
Last week’s storms filled most of the Salt River Project’s reservoirs on the Salt River to overflowing. As a result, SRP has opened up the floodgates, sending 70,000 cubic feet per second crashing down the normally dry Salt River bed through Phoenix, closing a host of crossings.
The storm caused flood flows in all the streams running off the Rim. Tonto Creek cut off people living on the wrong side of the creek and reportedly washed away a number of homes — mostly mobile homes sitting close to the often nearly dry stream bed.
Flows have already dropped from the peak. For instance, on Sunday the creek carried nearly 800 cubic feet per second where it flows into Roosevelt, but had declined to 142 cubic feet per second on Monday. Normal is about 39 cubic feet per second, according Salt River Project figures.
The Salt River, where it flows into Roosevelt Lake, on Monday carried 3,870 cubic feet per second, more than 10 times the normal flow.
Verde River at Trangle on Monday carried 2,930 csf, also nearly 10 times normal.
Most of SRP’s larger reservoirs were nearly 100 percent of their capacity by Monday — prompting dam managers to start draining water to make way for more runoff. In addition, a heavy snowpack across most of Northern Arizona should guarantee substantial spring runoff.
Water levels in Roosevelt Lake are approaching the highest mark ever — the second time the lake has been filled to capacity since SRP increased the height of the dam by 77 feet to provide extra capacity for flood control. The lake continues to rise as runoff thunders in, having already reached its full size of 21,500 acres.
SRP officials generally expressed satisfaction rather than alarm at the brimming reservoirs, after a decade of drought that at one point had nearly emptied Roosevelt. Once reservoir’s fill, the Valley can get through three or four years of drought without SRP curtailing its roughly 1 million acre feet in annual water deliveries.
All told, SRP’s reservoirs now hold about 2 million acre feet, including 1.5 million acre-feet in Roosevelt alone. In the past 24 hours, an additional 16,000 acre-feet flowed into the system. Payson uses about 1,800 acre-feet annually.
The weather service expects a succession of storms to amble into Rim Country this week, dropping snow levels to perhaps 5,000 feet, but delivering far less rain that last week’s monsters.
However, the El Niño pattern could reassert itself with a series of serious storms in February — maybe.
“We have episodes,” said Petro. “I don’t think we can yet say the whole winter is going to be wet, because there are breaks between each part of the cycle. It appears at the moment that we’ll have a week or 10 day of less precipitation — we’ll have to wait to see how it plays out.”
A pronounced warming of surface waters in the Eastern Pacific often produces a wet winter in the American Southwest. Evaporation from the warm surface waters causes a shift in weather patterns. The resulting mix of high and low pressure systems can shift the fierce, high-altitude jet stream to the south, which then captures winter storms in the Pacific and slams them into California and the southwest.
The pattern generally depends on the amount of warming at the ocean’s surface. Until last week’s storms, forecasters said they weren’t sure El Niño would deliver a wet winter this year, due to the “moderate” surface warming. They’re still not sure despite last week’s storms.
“El Niño is just one piece of the global circulation pattern,” said Petro, “so we can’t just look at this and say it’s going to stay wet.”
In fact, as of Monday, almost the whole of Arizona remains in “serious” to “severe” drought including all of Gila County. The heavy storm and the healthy snow pack may improve the situation, said Petro.
“We can’t say that just because we got x number of inches, we’re suddenly out of drought. Those numbers have yet to be calculated,” said Petro.