Commentary

Inventing the Whirlwind?

Is one of our most respected federal agencies guilty of inflating the number of named tropical storms in recent years? So writes Eric Berger in a recent Houston Chronicle article that got hyped around the world, thanks to Matt Drudge.

First, some unfaint praise: Throughout the years, the National Hurricane Center has probably saved more lives than just about any other federal entity. Yes, NHC has had a lot of technological help — satellites, radar, hurricane-hunter aircraft — but it’s easy to imagine what could happen without it.

Just go to Galveston, Texas, where in 1900, locals were hit by a Category 4 hurricane that remains the single most costly disaster in U.S. history in terms of human life. The storm killed between 6,000 and 10,000 people. By the time it was apparent that the city was about to be drowned, there was no exit.

NHC does one heck of a lot of good, but it is inflating the number of tropical storms. ”

Or consider last summer’s Hurricane Dean, probably the first Category 5 storm in human history to hit a populated shore without killing a single person at landfall. A similar storm, Janet, hit the same spot in the Yucatan in 1955 and killed over 600. Thank NHC and Mexican economic development for the difference.

NHC does one heck of a lot of good, but it is inflating the number of tropical storms. Today, there is a downward trend in the average maximum winds measured in tropical storms and hurricanes. This either means that the average storm is becoming weaker (for which there is no good scientific reason), or there are a larger number of wimpy storms being named.

Each named storm commands 24/7 coverage on the Weather Channel, and even the weakest hurricane will usually lead the news on Fox. Interestingly, Neil Frank, who ran NHC from 1974 through 1987, and is now chief meteorologist for WHOU-TV in Houston, agrees about hurricane-inflation, stating that “They seem to be naming storms a lot more than they used to.”

Back in Frank’s day, a tropical storm merited a name only if its maximum sustained winds appeared to be 39 mph or higher, if it had a significantly low barometric pressure, as well as a symmetrical cloud field consistent with what are known generically as tropical cyclones. “Tropical cyclone” is the scientifically correct name for both tropical storms and hurricanes, their stronger, 75-mph+ counterparts.

Nowadays, as was rather obvious with July’s tropical storm Chantal, it appears that winds alone are largely sufficient to name a storm. Satellite imagery showed nothing that looked like a tropical cyclone. Five other weak tropical storms this year also wouldn’t have met Frank’s barometric criteria.

Cynics might argue that NHC has a conflict of interest. After all, it releases months-in-advance estimates of the number of tropical storms and hurricanes forecast to appear each year. This year’s forecast indicated above-average numbers. Take away the six questionable ones and the year comes in as below average.

But that is cynical. There’s another good reason for naming relatively weak systems: even some of the wimpiest of tropical cyclones can cause massive flooding when they hit land.

The notion that tropical storms that never approached hurricane strength could produce unprecedented local flooding first hit home in 1979, when tropical storm Claudette — an unimpressive cyclone by any measure — suddenly dropped up to 42 inches of rain in 24 hours on Alvin, Texas, which remains the record daily total for the entire U.S.

Then tropical storm Alberto stalled over Georgia during the Fourth of July holiday in 1994, setting record crests on many southeastern rivers, killing 33 and leaving some residents of Macon, Georgia, without fresh water for 19 days. In 2001, tropical storm Allison hit the same region Claudette flooded in 1979, killing 22 in Texas, and becoming the costliest tropical storm in history, with $5.8 billion in damages in 2001 dollars.

None of these storms showed particularly impressive satellite signatures, and forecasters were shocked by the onshore flooding that ultimately ensued.

That’s one very good reason why NHC may be naming more weak storms now than they were. Even if some 39-mph weakling hits your beach, it’s now well known that double-digit rains are likely and inundation is possible. The problem is that naming and hyping everything, when only a few are bad actors, ultimately creates a public disregard (call it “hurricane fatigue”?) for dire warnings.

So let’s hang the jury and give the folks at NHC a break. They clearly are naming storms that would have been ignored decades ago, erring on the side of caution, because of the now-realized flooding potential of some very weak systems. But, in doing so, they’re also inflating the currency of the tropical cyclone, as people get tired of the seemingly continuous hype.