A downpour in Phoenix.

A flood on the East Verde.

October snow on just yellow aspen.

Severe drought on the Navajo Reservation.

A hurricane wading ashore in Mexico.

What’s the connection?

Global warming, according the National Weather Service and the National Oceanic and Atmospheric Administration (NOAA).

After a brief break from record-setting storms, the NWS says we can expect showers and thunderstorms through the weekend as the remains of Hurricane Sergio move thorough the Southwest.

Earlier in the week the hurricane had 90 mile an hour winds, feeding on the energy in the warm surface waters of the eastern Pacific. Another Hurricane — Michael — hit Florida on Oct. 10.

The National Weather Service says it’s unlikely Sergio or the related Tropical Storm Leslie will deliver as much rain to Arizona as Rosa did a week ago.

Rosa set an October record for Phoenix by dumping 2.4 inches in a few hours, the eighth heaviest day of rain in recorded Phoenix history.

In the mountains, Rosa dumped as much as 6 inches, topping the cloudburst that two years ago poured down on the still-smoldering face of the Rim — causing a flash flood that killed 10 people near Water Wheel on the East Verde.

The forecast for the storms hitting central Arizona over the weekend predict most of the rain will fall in southern Arizona, with only a “good chance” of heavy rain from the east Mogollon Rim through the White Mountains. The snow line may drop to 7,000 feet.

NOAA has issued a bulletin linking the mix of drought and deluge in the Southwest to the effects of global warming, linked to the release of heat-trapping gases by humans. Hundreds of studies have now linked both extraordinary drought punctuated by violent storms to the impact of global warming in the past 50 years.

Noah Diffenbaugh, a professor of Earth Sciences at Stanford University concluded, “It’s exactly what climate models project.”

Sea surface temperatures in Hurricane Rosa’s path were roughly 2-4 degrees F above normal. That much heat in the water not only drives hurricanes, it can also push eastern Pacific storms much further north than normal, delivering their rain to the Southwest.

The NOAA bulletin offered a summary of the ways in which the extra heat in the atmosphere drives more violent weather — both droughts and floods — across the globe, especially the Southwest.

For every degree of warming, the air can hold 7 percent more water — which it dumps as it moves inland and hits mountain fronts — like the Mogollon Rim.

Warming trends dry out the soils and spur increased drought, according to a host of studies. Unusually warm temperatures drove the severe 2011-2016 drought in California which have driven the worst wildfires in the state’s history.

The NOAA bulletin also cited recent meta analysis of climate studies, which have led to a scientific consensus that human-influenced global warming has already shifted the climate, with serious effects. Recent studies include:

A review of 216 studies published between 1995 and 2018 concluded “human-caused climate change due to greenhouse gas emissions was found to have a direct hand in 88 distinct climate change trends or events.”

Impacts in the United States included rising and extreme temperatures, coastal flooding, extreme precipitation events, reduced snowpack, increased drought risk, hydrological changes in the West, increased rain in the Northeast and North Central U.S., extreme hurricane seasons in the Pacific and increased wildfire risk.

Contact the editor 

at paleshire@payson.com

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