A large percentage of the public is at least roughly familiar with the concept of wind intensity being a measure of hurricane strength. The Saffir-Simpson wind scale is used to categorize hurricanes' intensity, and it looks like this.
By itself, this scale is a useful and time-tested measure of the winds which become increasingly destructive as velocity goes up. Winds are a key feature in what produces the potentially deadly and destructive storm surge. However, it has become apparent many in the public don't hear much once they get past talk of categorical weakening. Social studies have shown Category 1 hurricanes, tropical storms and tropical depressions draw far less public attention outside of the meteorological community because of this perceived weakening on the wind scale.
The responsibility for part of this lessened interest in other threats from a weakening storm may lie at the feet of the press and a minority of private sector meteorologists and weathercasters who are so emphatic about the categorical strength of tropical cyclones.
The NHC offers highly detailed advisories at least every six hours, which outline the flood threat produced by so-called "weaker" storms, particularly when they slow down. This includes easy-to-view graphics on rainfall amounts expected geographically and easy-to-read text on the likely impacts from such systems.
With the approach and passage of Florence, both the NHC and the National Weather Service Weather Prediction Center in College Park, Maryland gave both perspective and fairly high-resolution rainfall forecasts and expected impacts. This type of communication is never offered in a context of flooding, which poses a lesser threat. How that magnitude is handled in the press and by the public is another matter. Here are the actual fallen amounts displayed by the regional NWS River Forecast Center.
During the course of Florence's nightmarishly slow forward movement, here is one of the regular periodic "quantitative precipitation forecasts" from the NWS Weather Prediction Center.
All this information is constantly made available to the public. We know FEMA managers and local emergency management administrators do so constantly. But there is a large body of evidence many in the public don't look at this vital, potentially life-saving information, or choose to develop false confidence and do things such as drive into flooded roadways. Others are caught in place, in their homes, even in the face of Flash Flood Warnings or this rare "FLASH FLOOD EMERGENCY" issued by the Charlotte NWS on the 16th:
"This is a FLASH FLOOD EMERGENCY for central and southeast Mecklenburg County. This is a PARTICULARLY DANGEROUS SITUATION. SEEK HIGHER GROUND NOW!
* Some locations that will experience flooding include... Charlotte, Matthews, Mint Hill and Pineville.
Move to higher ground NOW. This is an extremely dangerous and life-threatening situation. Do NOT attempt to travel unless you are fleeing an area subject to flooding or under an evacuation order.."
Scientists like Dr. Marshall Shepherd, director of atmospheric sciences at the University of Georgia and a former president of the American Meteorological Society, write frequently for the public to give them more perspective on matters such as these. While he remains convinced, as do nearly all meteorologists, the Saffir-Simpson scale is very useful, its emphasis on wind is incomplete.
Shepherd told CBS News a few days ago, "The concept of saying 'downgraded' or 'weakened' should be forever banished. With Florence, I felt it was more dangerous after it was lowered to Category 2." University of Miami hurricane researcher Brian McNoldy said, "While you may still have a roof on your house because 'It's only a Category 1,' you may also be desperately hoping to get rescued from that same roof because of the flooding."
Not everyone agrees with my assessment that the NHC and NWS have communicated the other risks well. Susan Cutter, director of the Hazards and Vulnerability Research Institute at the University of South Carolina states NWS and NHC "have not done a good job at communicating the risks associated with tropical systems beyond winds." She says it's much harder to explain the other facts. "Wind is easy."
Before anyone thinks there's a push on for still another "index," I've seen no such effort. Dr. Rick Knabb, former director of the NHC stated, "One scale will never convey all hazards. Eliminating wind scale won't hide obviously weaker storms with life-threatening water. Also, please, no more scales to add to confusion. Instead of trying to categorize a storm, enhance location and hazard-specific warnings and decisions."
The fact that NHC erred some in the intensity forecast near landfall but excelled in the track and deadly flood threat is undeniable. What tropical meteorologists and emergency managers seem to be crying out for is a renewed emphasis on the threats posed by water, with even more specificity when the data allows it. Most of the information is getting disseminated, but something is getting lost in the translation, and many lives are at stake.