Useful Fools

Glenn Reynolds has commented about the level of hype associated with Hurricane Isabel. However, the comment “Category 2 Storm, Category 5 Hype” betrays a common misconception: that the category rating gives a good approximation of the danger to you. Lots of people say “I’ve ridden out a Category 2 before, so what’s the big deal?” But 1999’s Hurricane Floyd, “only” a category 2 hurricane, on the same track (and almost identical history) as Hurricane Isabel, killed 52 people and did massive damage. Hurricane Hugo was a category 2 storm until it was close to landfall, and then it rapidly intensified to category 4, causing massive damage.

Certainly the clubs at Baltimore’s Fells Point that had hurricane parties (hey, it’s only a category two) were surprised when they were flooded yesterday. The storm surge , amplified by Chesapeake Bay, combined with inland runoff produced by torrential rains, caused massive flooding. A record 6 foot storm surge came up the Chesapeake to Baltimore, yet, the category two winds didn’t even come close to Baltimore!

Contrary to popular opinion and media hype, the majority of hurricane deaths are not caused by wind, but rather storm surge flooding (which is related to the wind strength, wind area, distance from the eye, and especially topography) and inland rains. These are not closely tied to the Saffir-Simpson rating (category), which is based only on the maximum sustained winds (normally found in the eye wall).

In recent times. most deaths are caused by inland flooding from the storm’s rains (1998’s Hurricane Mitch killed an estimated 17,000 people, almost all from inland flooding), because with modern technology, storm arrivals are more predictable. Of course, this does no good if the warnings are dismissed as hype!. In contrast, devastating category 5 Hurricane Andrew had no deaths due to flooding, because the storm covered only a very small area, which was evacuated.

Inland flooding is related more to terrain, the speed of the storm and the size of the storm than the category. Also, a single storm surge could still kill thousands, as happened a number of times before modern sensing technology.

Emergency authorities were right to warn people that Isabel was a dangerous storm. It was big, thus having an unusually large wind area capable of causing storm surges over a wide area - more than folks who had “ridden out” other category 2 storms would expect.

Apparently, many people ignored the warnings of this “only category two” storm. As a ham operator working with the Hurricane Watch Net, I relayed messages to the National Hurricane Center of many boats and boat parts adrift at Virginia Beach, of docks underwater near Annapolis, and of large barns blown down. While the eye was still in South Carolina, people were losing power and trees in Pennsylvania!

There was a lot of damage from this “only category 2″ storm, and a number of deaths (last count: 14 18 28).

The message is to pay attention to the warnings from the official agencies in these storms. The media will hype the storm depending on the ratings value at the time, and will focus on wherever they have the best TV video. The NWS, National Hurricane Center, FEMA and many other agencies are concerned with avoiding death and damage, not ratings, and their warnings represent their best judgment and should be heeded. Finally, Hurricane prediction is not an exact science, so the storm may suddenly veer or intensify, causing a much higher risk than one might expecte by just watching the predicted central track.