New Orleans - The science involved in hurricane forecasting is constantly evolving. The payoff is a greater degree of accuracy and meteorologists have become much better at predicting where a storm will come ashore.
Some say we are not quite there, however, in other areas. Take, for example, the Saffir Simpson scale. It has not changed in decades and some forecasters worry this might be affecting public safety.
On the night of September 9, 1965 hurricane Betsy made landfall near Grand Isle with maximum winds of 130 mph. As bad as it was, we sometimes forget that years would go by before Betsy would first be referred to as a "Category three storm."
At the time, there was no such thing as the Saffir-Simpson Hurricane Scale. The weather bureau office, then located in Baton Rouge, could only describe the storm as "very dangerous."
It was the same case for Hurricane Camille in 1969. Years later, Camille would become infamous as a catastrophic category five.
But back in the 1960’s, the weather bureau was limited to issuing advisories with vague terms like "very intense" and "extremely dangerous" to warn the public.
With coastal populations growing ever-larger, it became obvious that a more detailed system was needed to classify storms. The goal was to make sure the public fully realized the potential for damage and destruction.
Two men, one an engineer and the other a meteorologist, collaborated on such a scale that was first put in place in 1973 and remains unchanged nearly four decades later. Herb Saffir, the engineer, created the wind scale after working with the United Nations to study damage to low-cost buildings from hurricanes.
“Because there were so many people being killed by storm surge, that Bob Simpson added storm surge values to that scale,” said Max Mayfield, the former head of the National Hurricane Center. “Now, those were generic values and it was never meant to be precise because we know storm surge depends on the bathymetry of the ocean, the orientation and the coastline, and the structure of the hurricane."
According to an interview with Dr. Simpson back in 2001, he is quoted saying "I often felt it was a bit premature to put the scale out without perhaps improving it a little bit, and at least educating the people as what is meant a little bit more."
And since its release almost 40 years ago, there have been many critics - especially those who fear the scale does not always fully explain the looming danger from storm surge.
Hurricane Ike's devastation in Texas is a recent example. Storm surge there has been compared to Camille, yet at landfall, wind speeds limited Ike on the Saffir-Simpson scale to a category two.
When you take storm surge estimates for each category, for example, a category three storm with winds of 130 mph should have an estimated storm surge of no more than about 12 feet. The problem is Katrina, a category three storm at landfall, had an estimated surge of almost 30 feet.
Many call for an update of the Saffir-Simpson scale to better express the storm surge potential. The problem is forecasting surge.
From coast to coast, along the Atlantic and Gulf, each state has very different coastlines and under water topography, called bathymetry, that affect the surge's potential for damage. LA alone has a difficult shore in terms of surge forecasting.
“Because of the complexities of the geology of Louisiana, a single storm would have dramatically different effects across the state,” explained Joe Suhayda of the LSU Hurricane Center. “As we saw with Katrina, Ike, and Gustav, each of those had their own separate tracks, but had dramatically different flooding potentials across the state."
Researchers at LSU, along with the University of North Carolina and Notre Dame are trying to perfect computer models that will forecast surge each time the national hurricane center issues an advisory on a named storm.
"One of our contributions is to make sure the modeling is based on good data. We do have the capability to do our own forecasts with an ADCIRC model that was developed at the University of North Carolina," said Suhayda.
"The primary forecast is based on the advisory from the hurricane center. What we're looking at for our own purposes is what happens if the storm deviates from that track or changes in intensity. So in fact if it increases in intensity, we would be running a run that evaluates that possibility. So it's not just a track, but parallel track and a more intense storm."
Good data is needed because as a storm is nearing the coast it starts to interact with different coastal feature and the computer model usually does not see this. So with all these uncertainties, the question is begged, how can you create a hurricane scale based on surge, when surge cannot be accurately forecasted?
"It's a very simple scale and it may be useful for the public, but for LA since the storm surge changes so much depending on what side of the levee we're on, what side of the delta we're on, that the storm surge aspects of the Saffir-Simpson scale could be potentially misleading," said Robert Twilley, Associate Vice Chancellor at LSU.
“We want to make people understand the impacts of all the hazards. You can't just focus on the wind, on storm surge, tornadoes or rainfall. All those hazards are important and all need to be talked about," Mayfield added.
But for the foreseeable future, the almost 40 year old scale will still be put to use each June 1.
