“Our biggest question is, ‘Where did the water go?’” said emergency-response meteorologist Tim Erickson during a recent trip to Freret Street to investigate.Of course we were all so extremely hunkered at the time that few of us would have had any eyewitness experience of street flooding anyway. But that sideways rain thing, that was real. Isaac's wind damaged the roof of my building flooding several units. It blew water in under the flashing on the roof at work, at my parents house and similarly damaged more than a few other buildings I happened to check on that week.
Most weather stations in the New Orleans area recorded 10 to 15 inches of rain during Isaac, but researchers have verified four gauges that recorded significantly higher amounts. One in Gretna recorded 23.96 inches; one at the U.S. Army Corps of Engineers office in Carrollton recorded 21.14 inches; another nearby at Audubon Park recorded 21 inches as well; and a station atop Andy Brott’s 43-foot tall home on Freret Street recorded 27.38 inches.
When the meteorologists climbed Brott’s roof to inspect his station earlier this month, they found a pole nearby that some rain might have slid down, increasing his total, they said. But that would likely only account for an inch or two of extra rainfall, they said, bringing it in line with the other three abnormally high readings.
In fact, when rain gauges fail during a hurricane, they most often under-perform, said National Weather Service hydrologist W. Scott Lincoln — because the rain blowing sideways is hard to catch.
“It’s atypical for gauges to over-report during hurricanes,” Lincoln said. “For four independent gauges all to fail in the same area, in the same way, the chance is very low.”
Isaac was a weird storm. But then I guess they all are.