New radar may help with tornado warnings

A graphic showing the levels at which radar scans.

GRAND RAPIDS, Mich. (WOOD) — Upgraded radar could allow the National Weather Service to detect tornadoes more quickly and get the warning out sooner.

When big tornadoes like those that happen in the Plains states form, they are easy to see on radar. Not so with the type of tornadoes West Michigan often sees. The small, EF-1 tornado that spun up in Wyoming on July 6, 2014 was too low and moved too quickly for the NWS to spot it on radar until it was close to lifting. A tornado warning was not issued and sirens weren’t sounded.

The problem is the frequency of the radar sweeps. Old radar conducted a scan of the lowest level of a storm about every four and a half minutes. A lot can happen in that four and a half minutes — the Wyoming tornado was on the ground for only six minutes, and it covered six miles and caused nearly $5 million in damage.

That’s why the NWS upgraded weather radars across the country with new technology called Supplemental Adaptive Intra-Volume Low-level Scan — or S.A.I.L.S., for short.

S.A.I.L.S. implements an additional scan of the lowest portion of the storm every two minutes.

“So very often, we’ll see a case when we don’t even see the tornado because it’s short-lived — less than a minute. So if you double that and seeing the lowest levels every two minutes, your chances of seeing the tornado are better,” said T.J. Arnage of the NWS in Grand Rapids.

S.A.I.L.S. technology is also important after the initial detection of severe weather.

“You are going to be seeing updates every couple of minutes then you can be a lot more precise and specific with the updated information,” Arnage said.

Rapid updates can be vital when storms are moving very fast. One of the worst storms in West Michigan history was the May 31, 1998 derecho. It had an average forward speed of nearly 70 mph, covering about five miles between scans. A storm moving that fast could nearly make it through an entire city during the old scan time of 4.5 minutes.

S.A.I.L.S. was running in West Michigan when a tornado tore through Portland two weeks ago, but that twister still didn’t show up on radar until it was too late to issue a warning and sound the sirens. That’s because Portland is some 40 miles from where the NWS Grand Rapids radar beam originates at a .5 degree angle. By the time the beam reached Portland, it was sweeping 2,500 feet, and the EF-1 tornado that spun up was lower than that.

So will the increased frequency of low-level radar scans lead to more timely and accurate tornado detection? Only time will tell. But with twisters here often weak in terms of tornadoes, low to the ground and hard to see, West Michigan is an excellent test ground.

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