7 November 2011 Tornadoes
The first tornado of the day is ongoing across portions of southwest Oklahoma. The tornado vortex signature (TVS) is located just to the northeast of Tipton, where the brighter reds and greens are side-by-side. Additionally, I should point out that the Oklahoma Mesonet has lost communication with the Tipton Mesonet station. With visual confirmation of a tornado in the vicinity, this would seem to suggest the tornado moved very close to, if not hitting, the Tipton Mesonet station. This would not be the first tornado to hit an Oklahoma Mesonet station this year. Back on 24 May 2011, the El Reno, OK EF-5 tornado moved close enough to the El Reno Mesonet station that debris wrapped around the Mesonet’s observing site. The strongest measured wind gust in Oklahoma history was recorded by the El Reno Mesonet station during the tornado’s passage.
On Any Given Saturday
Every Saturday during the fall, life in the southeastern United States comes to a stop. Attention turns toward college football and the escape from reality it offers. This break from reality has never been more needed for the city of Tuscaloosa, AL. Home to the University of Alabama, this city was devastated by a tornado during the historic 27 April 2011 tornado outbreak. Here’s a good story from ESPN on the impact of today’s Alabama-Kent State football game on the region.
One weekend in July, four Kent State players and a few athletic department officials came down to participate. One of them, senior running back Jacquise Terry, is from Phenix City, Ala., on the Georgia border. He played AAU basketball with Crimson Tide corner DeQuan Menzie.
“I have done Habitat before,” said Jacquise, who is minoring in construction management, “but I have never done it with players I compete with. That was the good part about it. We were able to put aside what we were about to do a month later and go in and help for a good cause. We fell right in together. They told us they appreciated us coming down. We bonded with those guys.”
Visual Comparison: 3-4 April 1974 and 27-28 April 2011
By the afternoon of 28 April 2011 it was fully apparent that the unthinkable had happened. In an era of unprecedented communication abilities, a single tornado outbreak took the lives of more people than all the tornadoes over the past several years combined – in broad daylight no less. In the days the followed, many tried to place this event into historical context. Nearly every one defaulted to the 3-4 April 1974 “Super Outbreak”.
The Super Outbreak was nothing short of impressive from a meteorological point of view. 148 tornadoes, 319 fatalities, over 13-states, in 24-hours. Never before, and not until this April, had anything even close to the scale of this tornado outbreak had ever been recorded. By comparison, the tornado outbreak of 27-28 April 2011 has an unofficial count (undertaken by several of us at the Storm Prediction Center) of over 174 tornadoes (done via Public Information Statements) and 259 fatalities attributed to these tornadoes. (Unfortunately, the death toll is considerably higher, I simply have been unable to place all the fatalities to the corresponding tornado at this time.)
From the standpoint of the number of tornadoes recorded and the number of fatalities, these two tornado outbreaks are in a class by themselves (in the “modern” tornado database starting in 1950). In the days that followed, I created a set of figures for internal NWS/SPC/NSSL use to compare the two tornado outbreaks. The images show all reported tornado tracks, color coded based on intensity and the counties are color-filled based on the number of fatalities that occurred within that county’s boundaries. A simple, quick look through the two events shows that the 3-4 April 1974 event covered a much larger area than the 27-28 April 2011 event, although there is considerable overlap between the two events. Several counties experienced fatalities in both events; in fact, Marion County, Alabama was unfortunate to have had a F/EF-5 tornado, and large loss of life, in both of outbreaks (1974: Guin, AL; 2011: Hackleburg, AL). Lastly, each figure has a table of the number of tornadoes and corresponding fatalities, broken down by EF-Scale (the 2011 event is still “preliminary” and subject to change). (Note, higher resolution images, for “zooming” are available by request.)
Meteorologists (and others) can, and will, debate for years as to which event was “more impressive”. I know what my thoughts are, but I’ll spare you those. However, please feel free to leave your thoughts in the comments.
The two images above are on the same background. This means if you download both of them and flip back and forth between the two, the only things that should change are the county colors and tornado tracks. Below is a zoomed in version of the 27-28 April 2011 event, complete with NWS County Warning Areas and County Names denoted.
Historical Arkansas Tornadoes
UPDATED: 11:30 PM CDT on 25 April 2011
The statistics have been updated to better account for tornadoes that crossed state boundaries. This added 32 tornadoes and 9 fatalities to the Arkansas counts. None of these additional tornadoes were rated violent tornadoes (F/EF-4 or greater). The Arkansas Tornado CSV file has been updated as well.
Several large tornadoes moved through Arkansas this evening, with the worst damage as of this writing coming from the town of Vilonia, AR. Several television stations from Little Rock are now reporting that parts of Highway 64 “are missing”. Anytime reports of pavement being scoured, the talk inevitably turns to discussion about tornado ratings, and comparisons to other pavement scouring tornadoes. Personally, I believe any talk of ratings tonight is premature, however, I went ahead and pulled the Arkansas historical record to help put this event in perspective.
Officially, there has never been a F/EF-5 tornado in Arkansas. Let me repeat that. There has never been an F/EF-5 tornado in Arkansas. In fact, there have only been 26 F/EF-4 tornadoes. If this tornado is rated a violent tornado (EF-4 or EF-5), it will rank among the strongest 2% of all tornadoes to strike Arkansas. If we limit to only tornadoes between 1980 and 2010, only 1.3% of al tornadoes were “violent” tornadoes. Even though most tornadoes are not violent tornadoes, almost half of all tornado fatalities in Arkansas (53) resulted from these 13 EF-4 tornadoes. The fact that there have been so few reported fatalities as of this writing (only 1), is a testament to the National Weather Service in Little Rock and their excellent warnings.
Click here to download the Arkansas Tornado Dataset in CSV format.
Arkansas Tornadoes and Fatalities (1981 – 2010)
Total: 998 tornadoes and 132 fatalities
In terms of all Arkansas tornadoes:
All Arkansas Tornadoes (1950 – 2010)
Total: 1587 tornadoes
Here are all Arkansas F/EF-4 tornadoes:
Keeping Perspective – Preliminary Vs. Final Tornado Reports
Over the last few days, the southern United States has endured a significant severe weather event that took the lives of a still increasing number of people. While many communities are still trying to sift through the wreckage, meteorologists, “meteorologists”, chasers, and other weather enthusiasts have taken to Facebook and Twitter to discuss what has happened. Unfortunately, a lot of misinformation is floating around. Here’s my quick attempt to clarify some of this information.
As of this writing, 248 preliminary tornadoes have been reported via the Storm Prediction Center’s Preliminary Storm Report webpage over the three days 14-16 April 2011. Much has been made about this number. Unfortunately this number contains many duplicate tornadoes, and potentially even some tornadoes that never were. Hence the label “Preliminary”. Over the next few weeks, National Weather Service Offices throughout the south will be conducting damage surveys to determine the number of actual tornadoes to the best of their ability. There is no doubt that this has been a significant three-day tornado outbreak. However, until the official numbers are released via the National Weather Service’s Storm Data publication, people should exercise extreme caution in trying to quantify where this week’s severe weather outbreak ranks in history.
It used to be the case that the preliminary number of tornadoes underestimated the number of actual tornadoes. However, near March of 2006 the pattern reversed itself with the number of preliminary tornadoes typically overestimating the number of actual tornadoes. For more information regarding preliminary vs. final tornado reports, please read this blog post on the topic by Harold Brooks, which can be found on the United States Severe Weather Blog.
In 2008, the final tornado count was roughly 75-80% of the preliminary count. Based on the number of spotters now reporting tornadoes, it’s not out of the question to assume this ratio is now closer to 70%, if not lower. Based on this an estimated guess to the number of final tornadoes might be closer to 198 (80%), 186 (75%), or even 173 (70%). Since I know people want to know below are the top three-day tornado counts on record using the final tornado numbers. The date given is the last day of the three days used in the count.
Three Day** Final Tornado Counts (1950 – 2010)
- 20040530: 184
- 20030506: 183
- 20040531: 172
- 19740403: 166
- 19920617: 152
- 20030508: 148
- 19740404: 147
- 20070506: 136
- 20070505: 135
- 20030510: 135
** The day listed is the end of the three days used in the counting.
To download the complete list, please click here.
Also, a disclaimer to the above list: This is a pure count of tornadoes over a three day period. A four-day period with tornado counts of 10, 85, 80, and 0 would show up twice even though for many applications, it probably should only count once. If you wish to throwout duplicate days, please refer to the dataset linked above.
It should be noted that the 75% ratio mentioned above was compute prior to the SPC removing a simple time and space filter. As such, the current ratio will most likely be even lower.
Drought and Tornadoes In 2006
As many already know, the southern plains is in the midst of a fairly pronounced drought. The drought reminds me of the drought we experienced in Norman during 2005-2006. During the drought, the rain stopped in late summer of 2005 and remained that way through November of 2006, when a very intense cyclone helped to alter the prevailing storm track.
As we head into the spring storm season, I’ve been getting asked more and more frequently how the lack of precipitation in the southern plains will affect storm season. The answer to this question is highly complex, and poorly understood at this time. However, I’ll offer one possible outcome.
The lack of southern plains precipitation, and more importantly, the dry soil, might allow the dryline to mix eastward faster than if the soil held more moisture. This, coupled with warm air aloft being advected over the southern plains from the higher elevations of New Mexico (which has also been extremely hot and dry of late), will help suppress thunderstorm and tornado development across much of western Oklahoma and the Texas Panhandle.
This is what happened in 2006, and you can see based on the graphic below, most of the tornadoes were to the north and east of western OK.
April Tornadoes
As we head into April, it’s time to update the plot of tornadoes by county for the current month. These data have been updated to include tornadoes in 2010. (Please note the modified color scale compared to January, February, and March.)
As you can see, the southern plains is becoming more as we approach late spring!
About Patrick
Patrick Marsh is a Ph.D. student at the University of Oklahoma's School of Meteorology. He earned a Bachelors of Science in Mathematics and Physics (cum laude) from the University of Arkansas in 2005 and a Masters of Science in Meteorology in 2007. In addition to working on his doctorate, Patrick serves as the National Severe Storms Laboratory Liaison to the Hazardous Weather Testbed where his research interests lie in working with operational forecasters, data mining, data visualization, and all things high-impact weather. For more about Patrick's work, check out his complete CV!
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