Forecasters see below-normal precipitation for monsoon season

A car splashes through an intersection in downtown Kingman following a monsoon thunderstorm last year. The outlook is for a weaker-than-usual monsoon season this year, according to the National Weather Service. (Daily Miner File Photo)

A car splashes through an intersection in downtown Kingman following a monsoon thunderstorm last year. The outlook is for a weaker-than-usual monsoon season this year, according to the National Weather Service. (Daily Miner File Photo)

We haven’t felt a drop of rain since March, with the last significant measurement of just over a quarter-inch on March 11, and the prospects of getting much from the summer monsoon season are pretty slim, forecasters from the National Weather Service believe.

The three-month outlook on precipitation probability from the National Oceanic and Atmospheric Administration shows dark green areas in the Northeast and along the Atlantic Coast, where probability is 100 percent.

There’s another green blotch in Colorado, and brown in the Northwest, indicating upwards of 50 percent chance.

As for Arizona, it’s going to be light, below-normal precipitation.

“Thunderstorms, what we call ‘convection,’ that occur during the monsoon season have been underperforming the last couple of years compared to climatology,” said Alex Boothe, meteorologist for the National Weather Service in Las Vegas.

“After a very disappointing winter, Mohave County and other surrounding areas could definitely use the rainfall from an active 2018 monsoon season, but that doesn’t look like the case.”

Monsoon season starts Friday and continues through the end of September.

The “monsoon” is actually a seasonal shift in the dominant wind patterns, but is commonly misunderstood as a nickname for summertime convection in the Southwest, Boothe clarified.

“Summertime thunderstorms are fueled by the moisture that these monsoon winds pull northward from the Gulf of California,” he explained.

According to the NOAA Climate Prediction Center, regional outlooks indicate higher chances for above-normal rainfall in the Four Corners region of Arizona, New Mexico, Utah and Colorado. Unfortunately, the outlook only gives equal chances over most of Mohave County.

“All that said, this weekend may provide a little relief and an early start to thunderstorms this monsoon season,” Boothe said. “Hurricane Bill, projected to weaken into a tropical depression as it moves into southern Arizona, will supply moisture, which may fuel thunderstorms in the Kingman area Friday and Saturday.”

Nancy Selover, state climatologist at Arizona State University, has seen some indicators suggesting a monsoon season that will be drier than normal, while others suggest wetter than normal.

The drier indicators are a warming of the equatorial Pacific Ocean surface temperatures, which portend a strong El Nino in the winter, Selover noted. It’s weakly correlated to a drier monsoon season.

“However, if those sea surface temperatures get much warmer than normal, it’s more likely we’ll have more eastern Pacific tropical storms which generate a lot of moisture that can get caught up into the monsoon flow in August or September,” she said in an email to the Daily Miner.

“The big storms of 2014 and 2015 were due to that additional moisture. The dry winter we had, which left the ground dry and very warm, may bring the subtropical high pressure over the state earlier than normal, meaning a possible early start to the monsoon. But, just because it might start early doesn’t mean it will be wetter.”

Another factor that confounds weather forecasters is where the subtropical high pressure will set up, Selover said. If it’s over New Mexico or western Texas, the circulation favors wet conditions in southeastern and eastern Arizona.

If it moves further to the west over northeastern Arizona, it could favor wetter conditions over the western part of the state.

“So for Kingman, the wetter conditions would likely occur if the high pressure is further west,” she said. “In 1993, the high pressure was over eastern and central Texas and most of the monsoon flow missed Arizona altogether and flooded the Mississippi River Valley all the way up to Minnesota. New Mexico got more rain than they normally get from the monsoon. We’ll just have to watch where the high pressure goes.”

Everyone prays for rain, but monsoon season can create havoc for Steve Latoski, director of Mohave County Public Works.

He’s in charge of maintaining more than 2,100 miles of county roads, and the randomness of storm damage takes his crews to specific areas such as Butler, Golden Valley and Dolan Springs.

Along with NWS warnings, Public Works monitors the Flood Control District’s ALERT flood warning sensors that measure precipitation and water flow gauges at various locations around the county, Latoski said.

Such alerts enable timely response to weather events as they unfold to close roads where needed, followed by repair work to reopen roads impacted by storms, he said.

Public Works has nine electronic message signs that are placed on Stockton Hill Road, Pierce Ferry Road, Hualapai Mountain Road and other high-risk flood areas to warn motorists of road and weather conditions. It also broadcasts travel information on AM radio channel 1610 on Hualapai Mountain Road.

“Frequent summer monsoons create a need for communicating accurate and timely information on weather-induced road closures and openings for benefit of residents, public safety services and public works staff directing incident response,” Latoski said.