Weather service aims to streamline flood forecastsNational Weather Service officials hope Fargo-Moorhead’s spring flooding will become a springboard to clearing up confusion caused by two types of flood predictions.
By: Mike Nowatzki, INFORUM
National Weather Service officials hope Fargo-Moorhead’s spring flooding will become a springboard to clearing up confusion caused by two types of flood predictions.
Officials from the NWS office in Grand Forks, N.D., met with members of local media outlets Wednesday in Fargo to reflect on the flood and how the weather service handled its role as information source.
“Our biggest challenge was communication,” said Mark Frazier, meteorologist in charge. “We had the information. It was how to convey it to our partners.”
Specifically, the agency is grappling with how to meld into a digestible format its two types of river forecasts:
- The seven-day deterministic forecast – displayed as a multicolored river level chart on the NWS Web site – is based on current conditions and the current weather forecast.
- The long-range probabilistic conditional outlook predicts river levels out 30 to 120 days, based on 50-plus years of past weather data and current hydrologic conditions.
People tend to focus on a single number, even though the outlook offers a range of flood possibilities by percentage, said Greg Gust, warning coordination meteorologist.
“We can give lots of numbers, but ‘the number’ is the one we know after it’s occurred,” he said.
One idea being considered to put the flood range into visual form is a river level chart with a line that widens into a cone to show the chances of the river going higher or lower.
“It’ll just give you one picture, one consistent message,” said Mike DeWeese, NWS forecaster at the Northwest River Forecast Center in Chanhassen, Minn.
Frazier said one of the hardest moments of this past flood fight came during a conference call with NWS regional and national officials trying to decide how to break the news that the Red River in Fargo could go as high as 43 feet.
“We had to make sure that we had that information as accurate as we could to give the most clear, concise information to those decision makers,” he said.
The information was released on March 26, and the Red crested at 40.82 feet on March 28.
The 43-foot figure not only reflected the uncertainty of how water would behave at a record flood level, but also was an attempt to put things into the terminology being used by city officials who wanted to build levees with 2 feet of freeboard, Gust said.
“We actually voiced it to them, ‘Well, it’s 41 (feet) with that freeboard to 43 (feet)’ … so that they weren’t saying, ‘It’s a forecast of 43 feet and we have to build to 45,’ because that’s not where we were really going with that,” Gust said.
NWS officials will host a similar post-flood meeting today in Grand Forks.
Readers can reach Forum reporter Mike Nowatzki at (701) 241-5528