Floating forecast

Weather balloon rises up to 75,000 feet to help SRP plan summer operations

If you happen to look up around 4:30 p.m. — or, if you’re a morning person, 4:30 a.m. — near SRP’s headquarters in Tempe, you might see a big white balloon taking flight.

But it’s not just any balloon. It’s a weather balloon that helps forecast high temperatures and storms in the Valley — a forecast essential to SRP’s summer operations.

During the monsoon, so much can change in just a few hours that it’s hard to make accurate short-term weather predictions. That’s where the balloon comes in. It helps SRP quickly forecast the needs of its electric customers, allowing for power production adjustments and surplus electricity sales. If storms are predicted, it also helps SRP ensure that enough employees are on call to address any power-related issues.

SRP hires interns from Arizona State University to do the early launches, and the National Weather Service (NWS) provides personnel for the evening launches. When the weather is active, a third balloon is launched at 7:30 p.m.

SRP and the NWS have partnered in the effort since 1998. The data helps NWS meteorologists identify the location of deep monsoon moisture and low- and high-pressure systems in the atmosphere to generate weather forecasts.


James Walter, Senior Staff Scientist/Meteorologist in the Surface Water Resources department at SRP said twice-daily releases occur from about mid-June through the end of September.


Balloon inflating

James Walter inflates the weather balloon, using a helium line on the roof of SRP’s headquarters in Tempe.

How it works

Before the launch, the balloon is inflated via a helium line. And because of proximity to Sky Harbor Airport, a call is made to the tower for approval to release it. Attached to the balloon is a radiosonde, an instrument that measures the temperature, pressure and humidity in the atmosphere. The device also includes a GPS antenna that calculates wind direction and speed.

Antennas on the roof of the Tempe headquarters receive data from the radiosonde in real time during the balloon’s flight. As it rises 55,000–75,000 feet into the sky, the balloon expands to about 9 feet in diameter and then pops — usually 30–40 miles away.

Total flight time: about an hour and 15 minutes.

The equipment is disposable and doesn’t have to be retrieved, but occasionally SRP gets a call from someone who has found it. When it’s a school, SRP employees sometimes visit to give students a weather lesson. But the most important outcome is the data received, which helps SRP better serve customers.


Photos and video by Heather Albert and Sonu Munshi

Heather Albert

Heather Albert

Heather is an Arizona native who works in Corporate Communications, overseeing SRP’s weekly employee publication. Outside of work, she likes to play sand volleyball, take her dog hiking, travel, read and bake pies.

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