Volunteer weather reports critical to flood forecasts

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WILMINGTON, Ohio (WDTN) – Heavy rainfall the last weekend of Feb. caused the water level of the Kentucky River and Ohio River to rise above the flood stage last week.

Julia Dian-Reed is a Service Hydrologist and Meteorologist at the National Weather Service in Wilmington, Ohio. Several Flood Warnings were issued last week. Dian-Reed said volunteers reporting rainfall totals are a critical part of the process.

“So, for issuing a flood warning and a flood forecast a key part is how much rainfall has occurred,” Dian-Reed said.

NWS Wilmington is encouraging people to volunteer to be a CoCoRaHS observer.

Anyone interested in reporting precipitation can register for a virtual training hosted by NWS Wilmington on Tuesday at 6:30 p.m.

“The training lasts about an hour and it talks about how the precipitation measurements are used,” Dian-Reed said.

Dian-Reed said they can estimate rainfall totals using doppler radar.

“There are very many times where it can overestimate rainfall or underestimate rainfall, so this is where the CoCoRaHS reports really come in handy,” Dian-Reed said.

CoCoRaHS stands for Community Collaborative Rain, Hail, and Snow Network. According to the CoCoRaHS website, the network started in 1998 at the Colorado Climate Center at Colorado State University after a flood in Fort Collins.

“There can be a lot of source of error in forecasting and weather forecasting. Sometimes we don’t get it 100% right. The weather is constantly changing and dynamic. The same is true for river forecasting,” Dian-Reed said. “If there’s not a clear picture just exactly what that snow water equivalent is on the ground or the exact rainfall amounts, that could definitely throw off a river forecast.”

Thousands of Volunteers are now contributing to those rainfall amounts through the CoCoRaHS network and they hope it will continue to grow.

“There was some record flooding along the Kentucky River,” Dian-Reed said. Having those CoCoRaHS reports again helps to verify the radar estimates because there were some cases where the radar was underestimating. So having those reports is critical.”

To start adding reports to the list volunteers must purchase a high capacity 4″ rain gauge.

“The CoCoRaHS network was founded on the principle of using the same gauge,” Dian-Reed said. “Everybody uses the same type of reporting gauge.”

She said it cost between $30 and $35.

“Set it up in a fairly clear area in your backyard away from your house and you report at a standard consistent time every day,” Dian Reed said.

The time highly recommended by CoCoRaHS is 7 a.m.

“However if a CoCoRaHS observer is observing large hail at the time or very heavy rain or flooding at the time, they can send us an instant report,” Dian-Reed said. “We do receive those alerting on our work stations. So, those are very handy during severe weather or flooding.”

Find a link to sign up for the virtual training here.

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