Wednesday, April 04, 2007

The Storm Season

In portions of the Great Plains, the Midwest and the South, the transition from winter to spring also marks the start of tornado season, the time of year when those deadly storms are most likely to occur.

Having lived most of my life in various parts of "Tornado Alley," I'm always a bit amazed by the national media's lack of interest in these storms--and their life-altering consequences. If tornadoes were a serious threat in New York or LA, we'd probably have a "Fox News Alert" every time a thunderstorm warning was issued for one of those areas. As it is, twisters are events that happen in flyover country or "Jesusland," and the national press really doesn't care, unless one of those monsters flattens a town and kills some unfortunate red-staters. At that point, as Jeff Foxworthy might observe, the camera crews and reporters descend on the disaster zone and look for the first local (preferably wearing bib overalls) who can describe the sound of the tornado.

For anyone with an interest in tornadoes--and efforts to predict them more accurately--, this week marks a pair of important anniversaries. Thirty-three years ago yesterday (April 3, 1974), the nation endured the so-called "Super Outbreak," an weather event that produced the greatest number of tornadoes (148) in a single, 24-hour period. The twisters devastated portions of 13 states and one Canadian province, killing at least 315 people, and inflicting more than $3.5 billion in damage (measured in 2005 dollars). Another massive outbreak in May 2003 actually produced more twisters (401), but those were recorded over an eight-day period.

Numbers aside, the Super Outbreak is also remarkable for the intensity and duration of the tornadoes that formed. Of the 148 tornadoes confirmed during the outbreak, 23 were rated as F4 on the original Fujita scale (with winds between 207-260 mph), and seven were classified as F5s, placing their top winds between 261-318 mph. The combined tracks of the Super Outbreak storms covered more than 2500 miles (another record); three of the twisters--which devastated communities in Indiana and Alabama--carved paths of destruction that were more than 100 miles long.

Xenia, Ohio is often remembered as ground zero for the 1974 outbreak. One of the event's legendary F5 twisters leveled much of the community shortly after four p.m., killing 33 people. It was the single deadliest tornado of the outbreak, although the town of Tanner, Alabama was (incredibly) hit by two twisters that day--within a 30-minute period--taking the lives of 50 residents. Other deadly storms on the afternoon and evening of April 3rd killed 31 people in Brandenburg, Kentucky and 30 more in Guin, Alabama.

The death toll might have been even higher if not for the efforts of the National Weather Service and the local news media, which provided warnings across the affected areas. Weather radars in those days were relatively crude, and weather service regulations required ground confirmation before a tornado warning could be issued. Despite those restrictions, forecasters issued more than 150 warnings, most within an eight-hour period between 2 and 10 p.m., central time.

Some of the broadcast reports from that day remain equally astonishing, despite the passage of time. Dick Gilbert, a traffic reporter for WHAS Radio in Louisville, "chased" an F-4 tornado in his helicopter, providing live updates that saved countless lives on the ground. In Dayton, Ohio, weathercaster Gil Whitney of WHIO-TV spotted a "hook" echo on the station's recently-installed radar and took the unusual step of issuing a tornado warning--ahead of the weather service. Without Whitney's warning, the death toll from Xenia tornado might have been even higher.

Could a similar-sized outbreak happen again? Certainly. The real question is how often such events occur. In the mid-1970s, the NWS categorized the outbreak as something that may occur once every 150 years, although that estimate is difficult to confirm. The weather service didn't begin keeping detailed tornado records until 1950, and there are few historical references, other than Tom Grazulis's superb Significant Tornadoes--1680-1991. However, future large- scale twister outbreaks will probably result in fewer fatalities, thanks to advances in radar, forecast and warning technology. Expansion and improvement of the NOAA weather radio system was a direct result of what happened on April 3, 1974. The next time that alarm goes off in the middle of the night, be thankful--and remember the events that helped produce that life-saving system.


This week's second tornado anniversary commemorates the April 2, 1957 storm that struck portions of Dallas, Texas. Better known as the Oak Cliff Tornado, the storm wasn't nearly as powerful or destructive as the twisters recorded in the Super Outbreak. But the Oak Cliff storm was significant in one important regard: it was the most photographed tornado in history (to that point), and yielded valuable evidence about a twister's windflow and life-cycle. Information gained from the Dallas storm (and a second tornado that hit Fargo, North Dakota two months later) provided the foundation for Dr. Ted Fujita's initial scale that estimated tornado wind speeds.

1 comment:

jamminedward said...

I cannot recall a tornado in NOLA in the 27 years I've lived here, but we had a small, but quite destructive one that cut a couple of swaths through neighborhoods on the up-river side of town in Feb. The Mississippi river does strange things to air flow above it (make an approach to Louis Armstrong Int'l Airport over the River, regardless of other weather, and you'll see what I mean) and the proximity of the huge Lake Pontchartrain, river and Gulf gives us remarkably stable temps and wind patterns. Seemed like those things combined to prevent tornado formation. Have to wonder if Katrina's accelerated devastation of coastal wetlands has changed the "airscape" such that we will now have tornadoes like a wet extension of the plains. Maybe they're just water-spouts run amok. Hmm, hurricanes, tornadoes, and bears, oh my!