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Weather Service upgrades will extend radar dome's coverage

Medford’s National Weather Service soon will be the first in the country to aim its radar below the horizon, leading to better real-time forecasts for severe weather events as far away as Coos Bay.

Since it was commissioned in April 1996, the Next Generation Weather Radar — NEXRAD — dome has sent out pulses of electromagnetic energy that gather data from storm clouds, including the intensity and size of rain and hail, as well as air circulation and wind speed.

But due to the Doppler radar dome’s placement — 7,513 feet above sea level — the curvature of the Earth and the fact that the radar beam drifts gradually upward the longer it travels, those pulses can overshoot rain falling from lower-elevation clouds. The data that bounces back becomes less and less useful the farther the pulses go, says National Weather Service meteorologist Ryan Sandler.

“By the time you’re over Coos Bay, you’re 20,000 feet above the ground, and the coverage isn’t effective,” Sandler says. “Same thing (if) you go over to Lakeview, and you’re 16,000 feet above the ground.”

Starting in September, new software will allow the radar to be tested at three new angles of elevation: 0.2 degrees above the horizon, 0 degrees and 0.2 degrees below the horizon. The Mount Ashland dome will be the first in the country to test scanning capabilities at all three angles.

“This has not been done below the horizon anywhere else in the country,” Sandler says. “We’re excited about it.”


The dome’s angle of scan is currently set at 0.5 degrees above the horizon. The new angle tests are seemingly trivial amounts, but they will make a world of difference in real-time forecasts, officials say.

“We’ll scan lower at farther distances, and we’ll see more rain, snow, hail,” Sandler says. “Whatever is there, we’ll be able to see it at lower elevations.”

These improvements will translate into better short-term forecasting, meaning better and more abundant data for forecasts that cover a span of hours, not days. Those who use weather radar apps on mobile devices will benefit from the improved accuracy.

Each site upgrade costs $65,000, which covers environmental assessments made to identify any issues stemming from the low amounts of radiation emitted by weather radar, which the World Health Organization has said are not harmful to humans. No issues were found, weather officials say.

There will be no additional cost for the software implementation itself, as it’s part of the regular work day, according to Jessica Schultz, Weather Service radar program manager, who is stationed in Oklahoma.

Dome placement

The main purpose of radar domes is to detect severe thunderstorms born of cumulonimbus clouds that lunge into the sky, sometimes as high as 60,000 feet. That’s where the emphasis was when the network was installed in the 1990s, Sandler says, and why the beam pulses need a clear view unhindered by mountains.

“We wouldn’t have had the budget years ago to build these radars, develop and build them, if it weren’t for all the tornadoes in Kansas and Texas and places like that,” Sandler says.

If the Mount Ashland dome were parked down low — say on the National Weather Service grounds a stone’s throw from the Medford airport — the beams it sent out would be noticeably impacted by the Siskiyou and Cascade mountain ranges that wreath the Rogue Valley. Even sent from atop Mount Ashland, radar beams encounter some blockage from Mount McLoughlin and Mount Shasta, weather officials say.

The dome’s height and angle of scan can be problematic when local meteorologists are attempting to seek information on inbound rain that is 100 miles out or more. It could be pouring in Brookings, Coos Bay or Alturas, but on radar, the activity will look trivial. The software changes should help that.

“The real benefit will be rain coming in to the coast,” Sandler says. “We haven’t run simulations, but we think we’re going to finally see a lot of this precipitation that’s coming in.”

“Now-casting”

The upgrade will not change the forecasting process, as meteorologists will continue to rely on computer models and observational data. But the radar will impact short-term or “now-casting,” which covers more immediate conditions.

“On my phone, I have a radar app,” Sandler says. “If you’re trying to decide, ‘Oh, can we get our baseball game in in Brookings?’ the radar’s useless to you. It won’t help at all. Here in Medford, it does help. You can see rain and showers moving in.”

Weather professionals will use this data to forecast weather that is more sudden and won’t last more than a few hours. This can be useful for flood warnings and advisories, hail and other severe weather events. Last year, the radar showed conditions were ripe for a tornado around Prospect, Union Creek and Crater Lake National Park. The short-term warning did not actually pan out, and the warning expired after about 24 minutes.

Lightning is not tracked by the information the radar dome gathers, but is followed by a separate network.

“Assuming we can see down to the rainfall at the coast, this could help a lot of people in that region make short-term decisions,” Sandler says.

Clutter

The increased amount of data and reach that will come with lowering the angle of scan has a small drawback — clutter.

In this case, the term refers to unneeded data when radar pulses bounce back. With a lowered scan, the potential for more clutter increases.

“When the radar beam intersects some type of obstruction or surface, then the energy comes back to the radar as what we consider ‘clutter’ or ‘erroneous return,’ ” Schultz says. “It’s not real weather. It’s a mountain or the ground or a building or something like that.”

This will not impact operations for the Weather Service, Schultz adds, saying it will be more of a “visual annoyance” than an actual problem for forecasters.

Next up

Some separate hardware upgrades are also planned for the local radar. A seven-year life extension program to keep the nation’s network of radar domes running into the 2030s has been ongoing since 2015. New receivers, signal processors and refurbishment of the dome’s pedestal are all part of the program.

It will cost $150 million to upgrade the 159 domes across the U.S., and all work should be complete by 2022.

Reach web editor Ryan Pfeil at rpfeil@rosebudmedia.com or at 541-776-4468.

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