Saturday, December 31, 2011

#1 Weather Disaster of 2011: Southeast / Ohio Valley Tornado Outbreak of April 25-28

The #2 weather disaster of 2011 (the Southern and Southwest Drought)currently carries a price tag estimated at $10 billion, but took place over a period of more than 9 months. This next disaster totaled $10.2 billion in damage and took place in a little more than 3 days!  I'm talking about the widespread, damaging tornado outbreak across the Deep South, Midwest and Ohio Valley of April 25-28 - which has the dubious distinction of ranking as the #1 billion dollar weather disaster of 2011.

The outbreak produced in excess of 350 tornadoes (see table below) and took the lives of 321 people.  Of those killed, 240 were in Alabama alone.  To date, a total of $7.3 billion in insured losses have been paid, with a total damage estimate of $10.2 billion.

Table of tornado outbreak data by state, via Wikipedia

For the duration of this post we'll take a look at the highlights of each day.

Monday, April 25, 2011:

The first day of the outbreak period produced a swath of over 40 tornado reports, extending from northcentral Texas into the mid-Mississippi Valley.

The most significant event of the day took place in Vilonia, Arkansas.  Most of the town was completely destroyed by a large tornado that struck shortly after 7:30 pm that evening.  Four people were killed and numerous others were injured.  Vilonia is located just North of Little Rock.

The picture below was taken just outside of Vilonia at about the time the tornado was taking place.  It shows what appears to be a large tornado at least partially obscured by rain:

An image from the Little Rock area doppler radar before the storm struck Vilonia shows a strong tornadic signature on both the reflectivity (rain and hail - left side of image) and velocity (wind speed and direction) images of the radar:

On the same image below, I've noted the location of a "debris ball" in a yellow circle on the reflectivity image and the strong rotational signature in the velocity image with a white circle:

A debris ball is a signature that is indicated when the radar is detecting debris that has been picked up and carried aloft by the tornado.  This is typically only observed with very strong and/or violent tornadoes, and when significant damage is being done.

Indeed, the damage in Vilonia was significant, with many homes completely destroyed or very heavily damaged:

Due to the strong signatures on radar, the city had over 30 minutes of warning before the tornado struck.  Undoubtedly the death toll would have been higher had that not taken place.

Tuesday, April 26, 2011:

On the next day, April 26, over 52 tornadoes were confirmed (of the 100+ reports received as noted on the map above), in a swath from northeast Texas across the Deep South and middle Tennessee Valley.  A few isolated tornadoes also took place in Michigan and New York state.

The strongest tornado that took place on the 26th was of EF-3 intensity, near Fort Campbell, Kentucky.  One structure was completely destroyed and several others heavily damaged on the Ft. Campbell Army Airfield, and several barns and homes in the city were also damaged or destroyed.

Unfortunately, the tornado events of the 25th-26th turned out to be only a "preview" of what was to come the following day... which would prove to be the most deadly and widespread tornado day in recent U.S. weather history...

Wednesday, April 27, 2011:

On April 27th, 2011, the most significant tornado outbreak in over 35 years took place across much of the Eastern third of the U.S.  Just over 200 tornadoes were confirmed on that day which shattered the old record of 148 twisters during the Super Outbreak of April 3-4, 1974.

The image below shows the preliminary tornado tracks across the South:

The following image illustrates the "killer" tornado paths of that day.  A total of just over 300 people were killed by 28 different tornadoes:

Hundreds of tornado warnings were issued from the lower Mississippi Valley into the Northeast on April 27th, a record number for any one day in U.S. weather history.  One National Weather Service ("NWS") office alone (Huntsville, AL) issued 92 tornado warnings on that day.  

Over 90% of the tornadoes that took place on April 27th did so inside of a Tornado Warning area, and 100% of the tornadoes took place within a Tornado Watch area.  These statistics make the staggering death toll of 300+ even harder to accept, at least when applying "conventional wisdom".  As it turns out, conventional wisdom isn't a very good barometer to use when it comes to the strongest of tornadoes, especially those of EF-4 and EF-5 intensity that track through heavily populated areas.

As the events one month later in Joplin, MO would further illustrate, seeking shelter above ground, as conventional wisdom would suggest (i.e., in a small interior room on the lowest floor of your home or business), is no match for a high end EF-4 or any EF-5 tornado.  A specially designed, below ground tornado shelter or an above ground tornado safe room offer the best chances of survival in these situations.

There were many "stand out" tornadoes that took place on April 27th (11 were of EF-4 intensity and 4 were of EF-5 intensity).  The events that took place in Alabama were particularly deadly and damaging.  In particular, the tornado that tore a swath of destruction from near Tuscaloosa: Birmingham:

...was on the ground for nearly 81 miles and had a damage path width of 1.5 miles at times.  The official NWS survey of the tornado damage path is shown on the following 3 images.  The colored triangles along the damage path refer to specific EF-intensity categories:  Blue = EF-0, Green = EF-1, Yellow = EF-2, Gold/Brown = EF=3, Red = EF-4:  

This tornado killed 64 people and injured at least 1500.  The official NWS survey rated this tornado EF-4, although I still contend that EF-5 damage was present at some points along the path, particularly in the Tuscaloosa area.

The supercell thunderstorm that produced the Tuscaloosa to Birmingham tornado was one of the longest lived (if not the longest lived) tornado producing thunderstorms of the day.  As you can see by the composite radar image below, the storm tracked from east-central Mississippi into southwestern North Carolina (a distance of over 350 miles) and was producing tornadoes most of the time!

I have made several posts on the blog this year regarding the Tuscaloosa and Birmingham area tornado.  You can view those individual posts here:

More on Tuscaloosa, AL Tornado of 4-27-11

Areal Footage of Tuscaloosa, AL Tornado of 4-27-11

Radar Imagery Associated with the Tuscaloosa Tornado

More on Birmingham, AL Tornado of 4-27-11

Another violent tornado, rated EF-5 intensity, tracked to the North of Birmingham on the 27th, impacting the Athens and Huntsville areas (among others in the region):  

This particular tornado was on the ground for 107 miles across north Alabama and extreme southeast Tennessee.  It produced a damage path up to 1.25 miles wide and killed 72 people.  

At least one major good came from the tragedy near Athens, thanks to this photo:

That is the Harrison family - and they were indeed saved by their tornado saferoom on April 27th.  You can see that it is literally the only room left standing in their home.  That photo and their story received world wide media attention (including here on the Original Weather Blog), and brought the issue of tornado saferooms and sheltering to the forefront of many peoples minds.

It is my hope that their story, as well as the story of Sam from Joplin, MO will lead many to purchase and install a tornado saferoom before the 2012 tornado season gets underway.

The Athens/Hunstville area tornado originated back to the Southwest near Phil Campbell, where several cases of EF-5 damage were observed, in that the foundations of frame built homes were wiped completely clean, as shown in this photo below (near Phil Cambpell):

Another tornado tracked between Birmingham and Huntsville, near Empire, AL on the 27th. This tornado took place in a rural area with no notable damage or injury (thank goodness), but I wanted to point it out and show this video to try and put to rest a widespread myth that tornadoes cannot travel over hills, mountains or other rugged terrain:

As you can see, this particular tornado had no problem with the rugged terrain of the region.  Had any homes or buildings been in the way, they would have been heavily damaged and/or destroyed.

While we're still talking about the area just North of Birmingham, another tornado, this one of EF-4 intensity, struck from near Cullman on Northeast to halfway between Huntsville and Albertville.  The following YouTube video showing the tornado moving right through Cullman is quite impressive, and is well worth waiting through the 25 second commercial at the beginning:

Here is another view of the Cullman tornado, taken by someone standing out in their front yard:

Watch that video again.  If you didn't notice the first time, take a look at the front door and/or yard of each house in the video...

Did you notice that there is a person literally standing outside every one of the houses, looking at and/or taking some type of video of the tornado.  Why were they not in their shelters?  Granted, in hindsight, we know that the tornado was moving right to left and did not directly threaten this particular location, but did the people standing out there know that at the time?  Also, keep in mind that the Tuscaloosa tornado threw debris up to 20 miles away from the actual tornado.  An area as close to the tornado as we are seeing in this video would certainly be under a threat of flying debris.

Continuing on with this theme, the next video was shot from the 3rd story balcony of an apartment building.  This appears to be the Tuscaloosa tornado but it is not positively identified in the video.  Listen closely and you can hear the person taking the video remark about the debris flying in the air overhead, yet he stays out on the balcony filming.  You finally hear someone in the background say that it's time to get inside, once it has begun to move away, of course...

Don't get me wrong.  I enjoy watching the videos so that we can learn more about tornadoes, etc., but I would much rather watch video taken by a trained spotter or storm chaser that knows exactly what their location is in reference to how the tornado is moving and is safely out of harms way.  In other words, "don't try this at home" unless you know exactly what you're doing!

Thursday, April 28, 2011:

The final day of the 4 day outbreak, April 28, 2011, featured 49 confirmed tornadoes, mainly along the Eastern seaboard and the far Southeast:

There were no EF-4 or EF-5 intensity tornadoes on the 28th.  There were 3 EF-3 intensity tornadoes, 2 in Georgia (one West of Griffin and one Northwest of Forsyth) and one in Virginia (near Bristol).  Unfortunately, each of these 3 stronger tornadoes were killers.  There were 2 deaths associated with each of the EF-3 tornadoes in Georgia and 3 deaths associated with the EF-3 tornado near Bristol, Virginia.  Each of these stronger tornadoes took place during the pre-dawn hours of the 28th (or late on the 27th, depending on how you want to look at it), which explains their absence from the map above.

The most significant damage of the day was in association with the tornado near Bristol, Virginia (right along the Tennessee/Virginia borders).   It caused major damage in the Glade Spring area, including a truck stop that was heavily damaged along I-81 (might want to mute the musical selection - not sure it fits the material - but the photos are impressive):

For a complete tabular listing of each confirmed tornado during the April 25-28 outbreak, I recommend this Wikipedia link.

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