Louisiana remembers Hurricane Isaac on 1-year anniversary

A satellite image of Hurricane Isaac over the US Gulf coast on August 28, 2012. (Source: NASA Observatory)
A satellite image of Hurricane Isaac over the US Gulf coast on August 28, 2012. (Source: NASA Observatory)

BATON ROUGE, LA (WAFB) - Hurricane Isaac made 'his' first landfall in Louisiana on August 28, 2012. Issac then made a "second" and final landfall near Port Fourchon (Lafourche Parish) at around 2:15 a.m. on August 29, which happens to also be the anniversary of Hurricane Katrina's Louisiana landfall.

The term "first" landfall is used because Isaac initially made landfall at about 6:45 p.m. along the southern portion of Plaquemines Parish, near the mouth of the Mississippi River, as a Category 1 hurricane (peak winds estimated at 80 mph). However, many may remember the storm's center then drifted to the west, moved back over open water and passed just south of Grand Isle.

A large and lumbering storm as it approached and crossed the Louisiana coast, Isaac's slow movement and large size pushed water into the tidal lakes (Maurepas and Pontchartrain), resulting in unprecedented storm-surge flooding along sections of Lake Maurepas. In addition, Isaac was also an efficient rainmaker. In dumping between 10" and 20" of rain over a large swath of southeast Louisiana (one site in Hammond reported more than 23" of rain from the storm), Isaac's rains rank as the largest storm event for that part of the state since 2001's Allison.

Utility companies estimate more than 900,000 Louisiana homes lost power for at least a short period of time and an AP report the following month indicated more than 58,000 homes received some type of damage from the storm. (An impressive number, given that it is more than one-fourth of the combined number of damaged residences that occurred with the 2005 monsters - Katrina & Rita.)

Isaac has become a "poster child" storm, of sorts, for further discussions regarding a re-assessment of the Saffir-Simpson (S/S) hurricane scale.

Recently, experts already had removed "storm surge estimates" that were once included in the S/S scale. Discussions regarding the operational utility of the S/S scale continue, as Isaac's size and slow forward speed - compounded by the complexities of the irregular SE Louisiana coastline and shallow coastal waters - will ultimately change how we evaluate storms in the future. Many remain surprised at the extent of inland damage from a storm rated "only a category 1" at landfall.

Look for the tropical-weather community to pursue the development of a tropical-cyclone scale that incorporates forward speed and overall size, as well as peak winds.

Certainly, the Saffir-Simpson scale has been a useful tool over the past several decades, especially for alerting the public about storm threats and allowing for general comparisons between past storms. But, we are reaching an end to our dependence on that classification scheme for warning and preparedness.

Storm-data gathering and computer modeling are taking us into a new era in storm forecasting and pre-landfall assessments. There remains much to do, but the tropical-weather community is already seeing the benefits of vastly improved wind-field and storm-surge forecast models associated with tropical cyclones. Emergency-management (EM) professionals and regional decision-makers are gaining access to impact tools and insights to potential storm threats that were simply unavailable just a few years ago.

What does this mean for Louisiana residents? We no longer should lean on Saffir-Simpson categories as a driver for our personal preparedness and response decisions. EM professionals - at the local, regional and state levels - have more information than ever to make better comprehensive evaluations of storm threats for the communities that they represent.

The bottom line: In the future, heed the recommendations of local EM professionals regardless of storm category. "It's only a Category 1" may not mean what you think!

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