Arizona Storm Spotters Capture Urgent Data For National Weather Service

Sep 9, 2015

A storm spotter's rain gauge in Somerton captured 4.6 inches during the heavy rainfall on September 8, 2015.
Credit National Weather Service-Phoenix

The National Weather Service relies on trained citizens to collect data during heavy rainfall, such as the record-setting storms seen in southwestern Arizona Tuesday.

A Somerton resident’s rain gauge collected more water during Tuesday’s storms than the area sees on average during an entire year.

Moisture from Hurricane Linda – now off the coast of Baja California – created what’s called a gulf surge. In the middle of the resulting severe storms in southwestern Arizona, a resident trained by the National Weather Service collected 4.6 inches in her rain gauge.

More than four inches of rain in Somerton is considered a 200-year event, which means there is only a half percent chance that the same amount of rain would fall in a single day during any given year.

James Sawtelle, a meteorologist with the National Weather Service in Phoenix, said storm spotters like the Somerton resident complement what meteorologists are able to see with radar and satellite imagery.

“Those are the volunteers that give us the ground truth of what’s really going on out there during storms,” said Sawtelle.

Several hundred individuals are trained as storm spotters by the National Weather Service in central and southwestern Arizona and southeastern California.

During storms, patches of heavy rain might not fall in a large enough area to be captured by official weather stations. So the data collected by storm spotters fill in these gaps and improves future weather predictions.

“The more resolution and the more detail your weather analysis has, the better your weather forecast is going to be,” Sawtelle said.

Yuma also saw a record amount of daily rainfall for September 8, with nearly an inch falling at the official National Weather Service gauge located at the Marine Corps Air Station.

Sawtelle said conditions are still in place to see more heavy rainfall in the area as humidity from Hurricane Linda travels up the Sea of Cortez.