North Carolina Sea Grant

March 20, 2015 |

By David Glenn

Posted March 20, 2015

David Glenn is the statewide coordinator for North Carolina’s Community Collaborative Rain, Hail, and Snow network. He is a meteorologist with the National Weather Service Forecast Office in Newport/Morehead City.

The race is on. As of March 20, North Carolina is the clear leader, with Texas a distant second.

March Madness isn’t just about college basketball. It also is a time when every state in the U.S. competes to recruit new volunteer weather observers for the Community Collaborative Rain, Hail, and Snow network, known simply as CoCoRaHS.

Of this writing, North Carolina is leading, with 116 new volunteers signed up, while Texas has 40. Our state is second behind North Dakota in new volunteers per capita count. Keep up with the standings here.

CoCoRaHS March Madness banner

The CoCoRaHS state networks compete to get the most new volunteers every March. Courtesy CoCoRaHS.

CoCoRaHS came about as a result of a devastating flash flood that hit Fort Collins, Colorado, in July 1997. Over several hours, a local severe thunderstorm dumped more than a foot of rain in some areas, while other portions of the city had only modest rainfall. The ensuing flood caught many by surprise and caused $200 million in damages.

In 1998, CoCoRaHS was born with the intent of doing a better job of mapping and reporting intense storms. As more volunteers participated, rain, hail and snow maps were produced for every storm, revealing fascinating local patterns that were of great interest to scientists and the public.

Map that shows rainfall amounts March 14 and 15, 2015.

Rainfall amounts from a cold front that crossed North Carolina March 14 and 15, 2015. Courtesy CoCoRaHS.

North Carolina became the 21st state to establish the CoCoRaHS program in 2007. By 2010, the CoCoRaHS network had reached all 50 states with nearly 10,000 observations being reported each day. Through CoCoRaHS, thousands of volunteers, young and old, document the size, intensity, duration and patterns of rain, hail, and snow by taking simple measurements in their own backyards.

In my opinion, one of the neatest things about CoCoRaHS is the ability to be part of history. While the network’s day-to-day observations are considered “unofficial,” the reports become very “official” during significant weather events — such as heavy snow with a winter storm, large hail from a thunderstorm or heavy rainfall from a hurricane.

Map of total rainfall from Hurricane Irene, August 28 and 29, 2011

Storm total rainfall accumulations on the U.S. East Coast from Hurricane Irene, August 28-29, 2011. Courtesy CoCoRaHS.

Volunteers may obtain an official rain gauge through the CoCoRaHS website for about $30 plus shipping. Besides the need for an official 4-inch plastic rain gauge, volunteers are required to take a simple training module online and use the CoCoRaHS website to submit their reports. Observations are immediately available on maps and reports for the public to view.

The process takes only five minutes a day, but the impact to the community is tenfold: By providing high-quality, accurate measurements, observers are able to supplement existing networks and provide useful results to scientists, resource managers, decision makers and other users.

Recently, drought reporting also has become an important observation within the CoCoRaHS program across the nation. In fact, the network’s drought observations now are being included in the National Integrated Drought Information System.

There are many users of the CoCoRaHS data. In eastern North Carolina, they include county emergency managers, area mosquito control programs, and the Shellfish Sanitation and Water Quality Department within the N.C. Department of Environment and Natural Resources.

In addition, the program allows the National Weather Service to receive timely reports of significant weather — such as hail, intense rainfall and localized flooding — from CoCoRaHS observers. This information can assist forecasters in issuing and verifying warnings for severe thunderstorms.

One goal of the CoCoRaHS program is to create a high-density network. However, we continue to have large data gaps along the coast. In spring 2012, North Carolina Sea Grant partnered with North Carolina CoCoRaHS to obtain three dozen rain gauges and place them in strategic locations along our state’s coast.

If you are interested in volunteering and live near the coast — or on a barrier island — please contact me at We can provide a gauge for your location.

Take a moment to share this information with any friends or family who have weather interests. Find the North Carolina CoCoRaHS network online or join it on Facebook.

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