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Tornado Outbreak Broke All-Time Records

Additional statistics on the massive tornado outbreak that struck several Central and Southern states from April 25 to 28 have trickled in, and they are downright shocking. According to figures compiled by the National Oceanic and Atmospheric Administration (NOAA), an estimated 305 tornadoes touched down during the entire outbreak. To put this in perspective, the previous record for the largest number of tornadoes in a single event was held by the “Super Outbreak” of 1974, during which 148 tornadoes occurred from April 3-4, 1974. 

Storm survey teams from NOAA’s National Weather Service have confirmed 197 of the 305 tornadoes so far, based on detailed investigations of the damage the twisters left behind. Many more such surveys remain to be completed in the coming days. If confirmed, NOAA’s estimate that 190 tornadoes touched down during the 24-hour period from April 27 to 28 would set a new record for the greatest number of tornadoes in a single day.

Tornado damage in Tuscaloosa, Ala. Credit: NOAA.

The death count from the outbreak currently stands at 318, which is actually down from previous estimates. The Tuscaloosa-Birmingham tornado alone killed at least 65 people — the most fatalities for a single tornado in the US since 1955. The deadliest single tornado on record was the Tri-State tornado that swept across Missouri, Illinois, and Indiana in 1925, killing 695 people. 

The Tuscaloosa-Birmingham tornado stayed on the ground for 80 miles and reached a maximum width of 1.5 miles. It will likely rank as the most expensive tornado of all time, according to Weather Underground’s Jeff Masters, and the overall outbreak is also expected to set a new benchmark for damage costs. 

I recommend reading Weather Channel senior meteorologist Stu Ostro’s in depth blog post on the tornado outbreak for a solid grounding in the factors that made the event extreme, and how climate change may be tipping the odds in favor of more extreme weather events (although not necessarily more or stronger tornadoes). Here’s how Ostro describes the weather conditions that were present during the outbreak: “The ingredients were "textbook." I mean, literally what I learned from a textbook more than 30 years ago.”

“Not only were the elements perfect for a tornado outbreak, they were present to an extreme degree,” he writes.

On the potential links between tornadoes and global climate change, which I covered late last week, Ostro states:

On the one hand there is no decisive trend in overall tornado occurrences, and while in recent years there's been a rash of outbreaks which have been unusually far north and intense for the time of year (including the one in Wisconsin last month), the one last Wednesday was geographically consistent with April climatology.

On the other hand, this event needs to be considered in the *context* of the relentless series of severe thunderstorm and tornado outbreaks which started on April 4 and culminated on the 27th. The number of severe weather reports and confirmed tornadoes has been atypical even by April standards, shattering the previous records. Even taking into account limitations of the historical record, the numbers have been stunning...

The atmosphere is extraordinarily complex, and ultimately what's happened the past month is probably a combination of influences, including La Niña, other natural variability, and anthropogenic [manmade] global warming.

New York Times blogger Andy Revkin also has a post that is worth reading, since it features extended remarks from some senior climate scientists about climate change and tornadoes. It also discusses the broader issue of society's vulnerability to extreme events, whether or not they are driven or aggravated by climate change.

To get a sense of how powerful these tornadoes were, one need only read some of the damage survey reports the National Weather Service has been issuing. Huntsville, Alabama TV meteorologist and American Geophysical Union blogger Dan Satterfield highlighted one damage survey report in particular, in a post titled, “The Most Amazing Storm Survey I’ve Ever Read.”

The survey found evidence that an EF-5 tornado — the most powerful classification under the Enhanced Fujita Scale — stayed on the ground for 132 miles, across northern Alabama and into southern Tennessee (it varied in intensity during this long trek).

Here are some of the startling details (the all-caps font is from the original document).

Here's what the survey team found in the city of Phil Campbell, Alabama:

CONTINUOUS SIGNIFICANT DEVASTATION THROUGHOUT THE CITY. PROLIFIC DAMAGE WAS NOTED FROM THE INTERSECTION OF COUNTY ROAD 51 AND ALABAMA HIGHWAY 237…TO THE INTERSECTION OF COUNTY ROAD 81 AND COUNTY ROAD 75. WITHIN A 2 MILE CORRIDOR EITHER SIDE OF THE RAILROAD TRACKS THE DAMAGE WAS SIGNIFICANT. WITHIN THIS CORRIDOR…SEVERAL WELL CONSTRUCTED HOUSES WERE DESTROYED. ALONG BROWN STREET…BLOCK HOMES WERE LEVELED TO THE GROUND. ALONG BONNER STREET…MULTIPLE BLOCK HOMES WERE LEVELED TO THE GROUND WITH THE BLOCK FOUNDATIONS DESTROYED. A 25 FOOT SECTION OF PAVEMENT WAS SUCKED UP AND SCATTERED. CHUNKS OF THE PAVEMENT WERE FOUND IN A HOME OVER 1/3 MILE DOWN THE ROAD. THE DAMAGE IN THIS AREA WAS DEEMED TO BE EF-5.

THE TORNADO CONTINUED TO TRACK NORTHEAST INTO LAWRENCE COUNTY AS AN EF-5 NEAR THE MT. HOPE AREA WHERE SIGNIFICANT DEVASTATION WAS INCURRED TO SINGLE FAMILY HOMES AND A RESTAURANT. NOTHING BUT THE FOUNDATION AND A PILE OF DEBRIS REMAINED IN THIS AREA…AND A SMALL PORTION OF THE RESTAURANT FOUNDATION BUCKLED. THOUSANDS OF HARDWOOD AND SOFTWOOD TREES WERE SNAPPED…WITH A SIGNIFICANT NUMBER OF TREES TWISTED AND DEBARKED WITH ONLY STUBS OF BRANCHES REMAINING. MANY MOBILE HOMES WERE ALSO DESTROYED WITH THE FRAMES MANGLED…AND A SINGLE FAMILY HOME WAS COMPLETELY DESTROYED WITH THE WALLS AND CONTENTS STREWN OVER A HUNDRED YARDS.

In Oak Grove, Ala., the survey team saw the following.

THE TORNADO MAY HAVE REACHED A RELATIVE MAXIMUM IN INTENSITY WELL INTO THE EF-5 CATEGORY AS THE DAMAGE WAS SLIGHTLY MORE INTENSE AND THE PATH WIDTH WAS AT A MAXIMUM OF GREATER THAN ONE MILE. A LARGE SWATH OF COMPLETE DEVASTATION WAS NOTED IN OAK GROVE ALONG COUNTY ROADS 38 AND SMITH LANE. A LARGE WELL CONSTRUCTED HOME WITH EXTENSIVE ANCHORING WAS RAZED WITH DEBRIS CARRIED WELL AWAY FROM THE SITE. A CORVETTE WAS MANGLED AND THROWN A MEASURED 641 FEET. ANOTHER LARGE VEHICLE IS STILL MISSING. A BLOCK HOME NEXT DOOR WAS ALSO DISINTEGRATED. ALONG SMITH LANE A BLOCK HOME WAS WIPED OUT AND THE ONLY REMAINS OF A NEARBY CHICKEN HOUSE WAS A SMALL PIECE OF A METAL TRUSS. IN THIS SAME AREA…THE TREE DAMAGE WAS COMPLETE AND A LARGE PERCENTAGE OF TREES WERE STRIPPED BARE.

Additional Resource: National Weather Service interactive map of tornado damage in the South.

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