Isaac has provided a timely reminder of the need for more comprehensive forecasts. Two fatalities in Braithwaite, La., near New Orleans, have now been tied to Isaac after floodwaters topped a levee in Plaquemines Parish. In addition, officials in Mississippi have attributed two deaths to Isaac.
Isaac's reversal of the Mississippi – and the resulting inland flooding – is the kind of effect scientists are striving to capture in new models.
One effort was triggered when hurricane Floyd did the same thing in 1999. Floyd's surge sent water coursing up rivers in eastern North Carolina, even as rain from the wide storm was hitting already saturated ground throughout the watersheds that fed the rivers. When water moving downstream met water flowing upstream, the combination had nowhere to go but out across the coastal plain.
Under development during the decade since, the Coastal and Inland Flooding Observation and Warning Program (CI-FLOW) forecast tool links measurements of rainfall and water flowing downstream with measurements and forecasts of tides, winds, waves, and storm surge.
A prototype system has been operating in North Carolina since 2010 and checked out reasonably well when "hindcasting" coastal surge and flooding during tropical storm Nicole in 2010, says Heather Grams, a research assistant at the Cooperative Institute for Mesoscale Meteorological Studies at the University of Oklahoma in Norman and a member of the CI-FLOW team.
When Irene traveled up the East Coast last year, the researchers ran it during the storm, and "we were pretty happy with its performance," she says.