Hurricane tag team of Rosa and Sergio set rainfall records for October

Clouds spun off from Hurricane Rosa move over metro Phoenix as seen from South Mountain. This month already is the wettest October on record, and more rain is in the forecast. (Photo by Jordan Evans/Cronkite News)

The record rains from Rosa and Sergio have not done much to refill SRP reservoirs, but they have improved soil moisture in the Salt and Verde river watersheds. (Photo by Jordan Evans/Cronkite News)

PHOENIX – First there was Rosa, then came Sergio.

Remnants of those downgraded hurricanes helped set rainfall records for Phoenix and made this the wettest October since record keeping began in 1895. Phoenix is 2.55 inches above the year-to-date normal.

The steady rains flooded roads, closed schools and briefly shut down the Arizona State Fair, but Arizona’s decades-old drought persists.

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In addition, heavy rain falling in a short amount of time doesn’t necessarily have a direct impact on filling underground water supplies or shoring up reservoirs – main sources of the Phoenix area’s water.

Bo Svoma, a meteorologist with Salt River Project, said the recent rain produced only “small inflows,” but that doesn’t mean the extra precipitation hasn’t helped.

“What it has done is that it has moistened up the watershed, which means the future storms we will see this winter will be much more productive in producing inflow into our reservoirs,” he said.

Svoma said Arizonans should not let their guard down about conserving water – especially because rain in metro Phoenix does not have a direct affect on the Colorado River. Arizona gets about 40 percent of its water from reservoirs on the Colorado, according to the Arizona Department of Water Resources.

And Arizona had a dry winter last year, which meant less snowmelt from the Mogollon Rim and eastern Arizona, which feeds SRP reservoirs on the Salt and Verde rivers, according to Cronkite News. SRP is the largest supplier of raw water to metro Phoenix.

The parking lot of Taylor Auto Sales floods whenever it rains. The record amount of rainfall this season hasn’t helped. Recent rains flooded roads, closed campuses and briefly shut down the Arizona State Fair. (Photo by Celisse Jones/Cronkite News)

However, this winter could bring some relief.

The Climate Prediction Center forecasts a weak El Niño for the Pacific Ocean, a climate pattern that’s expected to persist through the winter. For Arizona and states across the southern United States, that usually means a wet winter.

Earlier this month, the remnants of Hurricane Rosa made it across Arizona, which brought heavy rains across the Sonoran Desert.

At Phoenix Sky Harbor International Airport, rainfall measured 2.75 inches. That’s more than the total from this year’s monsoon season – June 15 through Sept. 30 – of 2.63 inches.

Ten days after Rosa, leftovers from Sergio hit, dumping 2.19 inches on Oct. 13.

Sky Harbor’s official rainfall total so far for October stands at 5.32 inches. That makes this the wettest October on record, and the fourth wettest month ever. Daily records for Phoenix date to August 1895.

If the airport gauge measures an additional 1.16 inches this month, October will become the wettest month on record. The National Weather Service has more rain in the forecast for this weekend.

This story is part of Elemental: Covering Sustainability, a multimedia collaboration between Cronkite News, Arizona PBS, KJZZ, KPCC, Rocky Mountain PBS and PBS SoCal.