Weather officials: Radar technology can't replace storm spotters
07/12/2014 7:53 AM
08/06/2014 12:13 PM
Weather officials in Tornado Alley are offering firm rebuttals to a national magazine article’s claim that new radar technology makes storm chasers “obsolete” and storm spotters virtually unnecessary.
In a Slate.com article titled “Why This Former Storm Chaser Now Thinks Stalking Tornadoes Is Unethical,” meteorologist Eric Holthaus writes:
“A recent nationwide upgrade to the National Weather Service’s Doppler radar network has probably rendered storm chasers obsolete anyway. The new technology, called ‘dual polarization,’ can help meteorologists confirm that a tornado is indeed causing damage. NOAA calls the upgrade ‘as good if not better than a spotter report of a tornado.’ In the early days of chasing, storm spotters were an essential part of real-time verification. Still, even without the recent radar upgrade, it takes only one or two reliable spotters on the ground (traditionally trained public service officers, like police) to confirm what weather radar is showing – not two dozen (or more) weather enthusiasts from out of town.”
The dual polarization radars recently installed around the country by the National Weather Service – Wichita was one of the first branches to receive the upgrade in 2011, with the final upgrade completed last year – have shown the ability to detect debris carried aloft by tornadoes. The “debris ball” shows up on radar and has become accepted as confirmation that a tornado is on the ground.
While that is valuable, weather officials say, it’s not enough to replace spotters or even storm chasers.
“The dual-pol debris signature won’t show up until something’s hit,” Harold Brooks, a research meteorologist at the National Severe Storms Laboratory in Norman, Okla., said in an e-mail response to questions. “If you want lead time before a tornado, it does no good. It may be useful in verifying warnings, but not in creating the first warning.”
The radars won’t detect a debris ball for every tornado, either.
“If it’s hitting a corn field or a wheat field, you’re not going to get the same debris field,” said Suzanne Fortin, meteorologist in charge of the Wichita branch of the National Weather Service. “It’s not going to be lofted as extensively,” making it more difficult for the radar to detect.
Dual polarization radars aren’t likely to pick up debris balls for tornadoes far from the radar – say, 50 miles or more – weather officials say. The EF-2 tornado that hit Baxter Springs on April 27, for example, was not detected by radar because debris was not lofted high enough.
Storm spotters and well-educated chasers have an important role even before a tornado develops, officials say.
“The benefit of the spotter is not just to report the tornado,” said Bill Bunting, chief of the operations branch at the Storm Prediction Center in Norman. “The benefit is also to accurately describe the precursor conditions.”
Is rotation increasing in the cloud base? Have winds flowing into the storm intensified? Have striations developed in the cloud formation?
“These are all pieces of the puzzle,” Bunting said.
Data collected during Vortex2 – a two-year field study of tornadoes in the nation’s midsection in 2009 and 2010 – suggests that factors closer to the Earth’s surface play more important roles in whether a tornado forms than previously realized. Discovering and detecting those factors could prove significant in determining which thunderstorms will generate tornadoes and which won’t, weather officials say.
That’s where observations shared by well-trained spotters or video provided by chasers live-streaming from storm locations can be vital, Fortin said.
“We show streaming video here all the time” in the Wichita branch, Fortin said. “You can see it unfolding. ‘Let’s take a look at what we’re seeing’ ” on radar.
Dual polarization radar has added an important tool to provide confirmation of a tornado on the ground, Fortin said, but it won’t replace storm spotters.
“We’ll always rely on spotters,” she said. “They are essential to our warning decision process.”
Contributing: Associated Press