Tuesday’s sessions at the National Hurricane Conference focused on looking back at the two storms that had a big impact to the United States, hurricanes Isaac and Sandy.
While Sandy will go down in history far more significantly than Isaac, Isaac is probably more relevant to those of us in the Houston-Galveston area. Isaac produced serious flooding in southeast Louisiana, outside the levees due to storm surge and on rivers and bayous due to excessive rainfall. Isaac was a large and slow-moving storm, almost stalling as it made landfall. The size and slow motion were the main factors contributing to the abnormally high storm surge and rainfall totals in excess of 20 inches.
In spite of good forecasts of the storm surge, many people in the impacted communities were surprised. Scientists from Florida State and University of Miami conducted surveys of the population and found that in general people over estimated the threat of wind damage and underestimated the threat of surge or rainwater flooding. This is a similar finding from surveys conducted during Irene and Sandy. One of the recommendations to mitigate this misconception is that the National Hurricane Center issue Storm Surge Warnings.
Most of the discussion was, understandably, focused on Hurricane Sandy. While the numbers are still being assessed, Sandy will likely come in just below Katrina in terms of dollar damage. Given the huge size of the storm and densely-developed coastal area Sandy struck, this should not be surprising. Presenters pointed out that there were two disasters – the direct impact of mainly storm surge flooding to literally hundreds of thousands of homes followed by a critical power outage to over 8 million customers.
The picture above shows the track of Sandy in white and all the forecasts in black. The forecast of both track and intensity was much more accurate than average. I show this to point out that even a good forecast will not change the fact that in the end, the storms will hit and a lot of damage will occur.
Mitigation – what you can do to reduce your risk – will be the topic of discussion on Wednesday.