This past weekend, millions of Americans have been preoccupied with Monday’s deadline for filing their 2010 federal income taxes.
But from Thursday through Saturday, those who had any spare time to look out the window or turn on the news might have had occasion to notice the largest tornado outbreak since April 3-4, 1974. Back then, some150-170 tornadoes hit 13 states, killing over 300.
In fact this past weekend’s outbreak may prove to have been the largest ever. Some preliminary estimates put the number of tornadoes at 200 or more in 14 states (extending from Oklahoma and Arkansas in the Midwest, then southward through Mississippi and Alabama, then curving northward toward the northeast, up through the Carolinas, Virginia, and Maryland). The death toll? A lot less than decades ago. Maybe as few as 50 people.
50 deaths is still 50 too many. These fatalities and the pain and suffering of the survivors cannot be measured, and cannot be swept under the rug. And, in coming weeks, as the National Weather Service and others inventory the victims, the property damage and the economic disruption, we’ll all see opportunities for improvement: longer lead times for watches and warnings, greater public awareness, improved design of homes and other structures. But the fact remains that we’ve made progress in all these areas over recent decades.
We should continue to make this a priority. Our population is growing, especially in tornado-prone areas of the country (as opposed to the northern tier of states). Decades ago, tornadoes would most often hit largely rural countryside. Today those same areas are built-up, on the urban fringe. Tornadoes encounter what the military would call a target-rich environment. [The same is true of hurricanes and other coastal storms, as the nation’s shoreline has become increasingly populated.] If we fail to maintain focus on this threat, tornado casualties will start to rise again in coming years.
A quick aside: Did you know that tornadoes are as American as apple pie?
That’s true. The United States has arguably the most dangerous weather in the world. On average, we experience about the same number of winter storms each year as they do in Europe, or Russia, or China. Hurricanes? We see about as many as do the Philippines, or China, or Japan. But we are exposed to many more dangerous thunderstorms, and we have a virtual lock on tornadoes – maybe as much as 90% of the world’s total, and an even higher percentage of the bigger, more dangerous ones. Europe, or Australia, or China might see a handful. But we have 1000 per year on average. If the eagle is our national bird, and the oak is the national tree, the tornado should be our national weather hazard.
The past few posts have focused on our national investment in monitoring the Earth as resource, victim, and hazard: some $10B/year. Some of that investment has been directly responsible for reducing the deaths from tornadoes since the April 1974 outbreak.
Back in the 1980’s, we replaced a 1950’s vintage weather surveillance radar network, based on vacuum-tube technology, with a new network, totaling perhaps 150 newer units. Going by the name NexRad (Next-generation Radar), this system had what was referred to as a Doppler capability, which enabled it to directly measure wind speeds inside thunderstorms, and distinguish between those that might just cause heavy downpours, and those that might likely spawn a tornado. It was developed and implemented collaboratively through the efforts of NOAA, the FAA, and DoD.
The earlier 1950’s system had to rely on the appearance of so-called “hook echoes” to reveal tornadoes. Between that and the volunteer spotting network, tornadoes were on the ground and average of several minutes before the warning would go out, and the false alarm rate was 67%. In other words, two times out of three a tornado warning would prove to be in error!
Today’s NexRad systems buy maybe ten minutes’ advance notice on average, while the false alarm rate drops to something like 25%. Those 150 radars, installed over a decade? They cost maybe $1.5B, or $150M/year [roughly $10M each]. The payoff in public safety? Dramatic. [The AMS has just published a book on the economics of tornadoes, weather radars, and weather warnings.]
It would be reassuring to think that we invested in the new generation of radars because we could see this opportunity to save lives. But here’s the real truth. We invested in NexRad primarily because those old radars were simply worn out. The antennas rotated on pedestals to get a full-sky view, and the 30-40-year-old pedestals were failing mechanically. And the vacuum tubes needed for the old transmitters were no longer commercially availably. They had to be rebuilt individually, or cannibalized from other units. We couldn’t continue to operate the old system, at any cost.
Today, we stand on the threshold of new level of radar protection, and essentially for the same two reasons. We have to replace the 1980’s radars, because now they’re wearing out. But the new radars will likely be even more capable. They can be based on a new phased-array antenna technology. The radars will no longer have to be steered mechanically. They can be steered electronically, and at much higher rates. They can scan a full sky in seconds instead of taking five minutes. We owe this technology to the military. It was developed for Navy vessels to handle the threats posed by incoming aircraft and missiles. But it’s going to have great peacetime applications, thanks to work at NOAA’s National Severe Storms Laboratory and several defense contractors.
These higher scan rates will enable forecasters to see tornadoes develop more quickly, and earlier-on in the storm life cycle. Their warnings can be that much more definitive. But wait! It gets even better. The new radars will also have dual-polarization — a fancy term for the ability to distinguish between heavy rain and hail. Forecasters will no longer have to guess.
Back to those tax returns we’re filing before Monday. You and I won’t be paying just yet for these new radars. Folks in Congress and the Executive Branch are still debating that. But when we do get around to it, some year down the road? The hit will amount to something like one penny out of every $1000 of the federal taxes we pay.