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Research / Discovery

Rain, hail, snow: CoCoRaHS volunteers report it all

February 19,2014
By Kortny Rolston

When CSU launched the Community Collaborative Rain, Hail & Snow Network in 1998, only a handful of volunteer weather observers participated. Today, more than 19,000 volunteers track and report precipitation data each day through CoCoRaHS. The American Meteorological Society recently honored CoCoRaHS for its success.

Between 5 a.m. and 9 a.m. each day, color flows into the interactive weather map on the Community Collaborative Rain, Hail and Snow Network website.

Shades of green, blue, red and orange dot areas where rain, hail or snow measurements have been reported by the network’s 19,000-plus trained, volunteer weather observers.

The CoCoRaHS map contains some of the most detailed, accurate precipitation data in the country – and it’s available to the public at any time.

That the program, which Colorado State University started in 1998, has morphed into a national phenomenon amazes Nolan Doesken, CoCoRaHS director and state climatologist.

“Every single day we, with the help our volunteers and their reports, create a map for anyone to look at,” he said. “You can track rainfall and snowfall patterns across the United States. It’s a great public resource.”

It’s also why CoCoRaHS recently was honored by the American Meteorological Society with a special award for “building a community of over 15,000 volunteer observers dedicated to providing high-quality, reliable observations of daily precipitation across the United States.”

“It’s a big honor for all of the volunteers that contribute to the network,” Doesken said.

The start of CoCoRaHS

Doesken and his CSU colleagues launched CoCoRaHS in 1998, not long after Fort Collins – and the University – experienced widespread flooding and subsequent damage.

The amount and toll of the flooding caught many by surprise.

“We decided then that we needed to start documenting how much rain we were getting and make it more available to weather forecasters so we weren’t caught off guard again,” Doesken said. “We wanted to be able to track and record it better so we could alert people earlier.”

The CSU team started training local volunteers to accurately record and report precipitation data. The volunteer network grew over the next few years and spread to other parts of Colorado.

There was a point, however, in 2002 when organizers thought the network might collapse.

The severe drought squeezing Colorado that year caused interest to wane.

“People were bored silly trying to measure rain when it wasn’t raining,” Doesken said.

The network survived the drought and slowly gained more attention.

In 2003, the National Science Foundation provided CoCoRaHS funding to expand into Wyoming, Nebraska and Kansas

“Once we proved we could do this in  rural states, it just took off,” Doesken said.

Over the next decade, the number of trained CoCoRaHS volunteers swelled to more than 19,000 in all 50 states and into Canada. (When the network was nominated for the American Meteorological Society award, it had 15,000 volunteers.)

More than 28,000 volunteer observers have participated in the network since its inception.

The human touch

To organizers, it’s the human element that sets CoCoRaHS apart.

While weather monitoring technology has evolved since 1998 and many larger cities like Fort Collins have invested in a high-end flood warning system  , experts say so far, there is no replacement for trained human observers with an interest in reporting precipitation.

Technology can break down, disrupting data, and can be costly to install. Today’s sensors also have limited ability to accurately measure hail and snowfall.

“The most accurate measurement of precipitation is still taken by motivated humans with proper equipment,” Doesken said. “Manual data still has a place in this high-tech world of ours.”

"A beautiful thing"

Even after 16 years, the CoCoRaHS organizers still enjoy watching data flow into the network’s online climate map from across observers around the country.

“It’s a fascinating and beautiful thing to watch,” Doesken said.