Hurricane Isaias streamflow forecast: a qualitative retrospective
Before Hurricane Isaias reached the Gulf Coast, we published 18-hour streamflow forecasts for 12 Alabama watersheds. This follow-up compares those forecasts with the USGS observations that followed. Because we have the completed graphics but not the underlying time series here, this is deliberately a visual, qualitative assessment rather than a calculation of forecast skill.
Isaias made landfall near Destin, Florida, as a Category 2 hurricane at 01:30 UTC on October 10, crossed southern Alabama, and became post-tropical that morning. After unusually strong seasonal wind shear briefly relaxed, Isaias intensified from Category 1 to Category 3 overnight before weakening ahead of landfall, as Scientific American reported. The rapid intensification made Isaias a powerful storm, but its track and the placement of its rain, not its category alone, determined which watersheds responded.