The National Weather Service office in Medford is upgrading a key piece of equipment meteorologists use to gather weather data, a move officials say will result in more accurate forecasts.

The National Weather Service office in Medford is upgrading a key piece of equipment meteorologists use to gather weather data, a move officials say will result in more accurate forecasts.

The upgrade comes in the form of tiny sensors called radiosondes. The devices are attached to weather balloons, which are launched twice a day. During a 90-minute ascent to an altitude of about 100,000 feet, the sensors transmit data back to NWS computers.

"It will take temperature, the relative humidity and the pressure," said NWS meteorologist Mike Ottenweller.

The Medford office was one of 24 NWS locations in the U.S. to receive the new radiosondes — out of 102 stations in North America, the Pacific Islands and the Caribbean, and more than 800 locations worldwide. The award was based on the Medford station's history of forecast accuracy and its proximity to the Pacific Ocean.

"We're kind of the entry point for these systems that are going to affect the rest of the United States," Ottenweller said.

Where the old radiosondes transmitted data every second or so, the new RS-92 model broadcasts every one-sixth of a second.

"The whole system is designed to eliminate any errors," Ottenweller said.

After reaching the peak of its ascent, the weather balloon bursts. A small parachute opens and carries the radiosonde back to earth. The devices typically land somewhere east of the Cascades, Ottenweller said. A prepaid mailing envelope is attached to each transmitter, which finders can use to send the device back to NWS offices. The radiosondes cost $250 each, but only about 20 percent of them are returned nationwide. Locally, that rate is even lower.

"There's so much wilderness in the surrounding area," said meteorologist Brian Nieuwenhuis. "They land out in the middle of nowhere and nobody will find it."

Locations for the few balloons that have been found and returned include Klamath Falls, Bonanza, Grizzly Peak and spots around the Siskiyous.

The inaugural launch for the new radiosondes will be at 3 p.m. today. "We're very much looking forward to being part of this Phase 2 to gather information more accurately, more effectively," Ottenweller said. "We're very excited to be transitioning."

Reach reporter Ryan Pfeil at 541-776-4468 or rpfeil@mailtribune.com.