Flood forecasts in flux

How high will the flooding go? That's been a crucial question for Midwesterners this month, and the answer requires some complex - and changeable - figuring.

Forecasting the rise of the rivers is a cross between predicting the weather and predicting a traffic jam, experts say. The good news is that this summer's flooding is something of a slow-motion phenomenon, providing time for communities to shore up their defenses. The bad news is that the lessons from the last monster flooding in the Midwest, back in 1993, have gone largely unlearned.

First, about that good news: Flood forecasts, like weather forecasts, are the province of the National Weather Service - and technological advances have generally improved the quality of the flood-warning system just as they have for other aspects of severe-weather warnings.

"The folks in the field have barely had time to catch their breath, but for the most part we haven't had negative feedback - except that everyone always wishes we had it exactly right the first time," said Noreen Schwein, manager of the hydrologic services program at the weather service's Central Region Headquarters in Kansas City, Mo. The Central Region takes in the entire area of flooding in Iowa, Wisconsin, Missouri and Illinois.

Robert Criss, a professor of earth and planetary sciences at Washington University in St. Louis, agreed that the forecasts have been "remarkably accurate" - within the limits of the system, that is. He noted that the flood wave is working its way down the Mississippi River at about walking speed, giving the forecasters time to analyze the water's course, and giving emergency officials time to react.

"It's like a traffic jam. The cars move slowly through the jam, and this big stuff is coming our way slowly and inexorably," Criss said from his office in St. Louis. ...

•	Flood forecasts in flux Cosmic Log MSNBC.MSN.com, Wednesday, June 18, 2008 Byline: Alan Boyle, MSNBC.com science editor