Video 1. Remarkable video of the tornado that hit Tuscaloosa, Alabama on April 27, 2011. Fast forward to minute four to see the worst of the storm.

Figure 1. A truly frightening radar image: multiple hook echoes from at least ten supercell thunderstorms cover Mississippi, Alabama, and Tennessee during the height of the April 27, 2011 Super Outbreak. A multi-hour animation is available here.

A record six EF-5 tornadoes confirmed in 2011
Six top-end EF-5 tornadoes hit the U.S. in 2011, tying this year with 1974 for the greatest number of these most destructive tornadoes. The EF-5 tornadoes of 2011:

1) The April 27, 2011 Neshoba/Kemper/Winston/Noxubee Counties, Mississippi tornado (3 killed, 29 mile path length.)

2) The April 27, 2011 Smithville, Mississippi tornado (22 killed, 15 mile path length.)

3) The April 27, 2011 Hackleburg, Alabama tornado (71 killed, 25 mile path length.)

4) The April 27, 2011 Rainsville/Dekalb County, Alabama tornado (26 killed, 34 mile path length.)

5) The May 22, 2011 Joplin Missouri tornado (158 killed, 14 mile path length.)

6) The May 24, 2011 Binger-El Reno-Peidmont-Guthrie, Oklahoma tornado. (9 killed, 75 mile path length.)

Figure 2. Aerial view of damage from the May 22, 2011 Joplin, Missouri tornado. Image credit: Wikipedia.

Figure 3. EF-5 damage from the April 27, 2011 Neshoba tornado in Mississippi. The tornado was so powerful that it dug out the ground to a depth of two feet over an area 25 – 50 yards wide and several hundred yards long. Image credit: NWS.

A few other remarkable statistics on the tornado season of 2011, compiled from NOAA’s official press release, the NOAA Extreme Weather 2011 page, and Wikipedia’s excellent tornado pages:

- The tornado death toll of 552 in 2011 ties 1936 as the second deadliest year for tornadoes in U.S. history. Only 1925, with 794 fatalities, was deadlier. In 1936, violent tornadoes hit Tupelo Mississippi (216 killed), and Gainesville, Georgia (203 killed.) During the 1930s, the tornado death rate per million people was 60 – 70 times as great as in the year 2000 (Figure 4), implying that this year’s tornadoes may have killed tens of thousands of people if we did not have our modern tornado modern warning system.

Figure 4. Death rate per million people per year in U.S., 1875-2000. Thin line with dots is raw rate, curved thick line is death rate, filtered by 3-point median and 5-point running mean filter, and straight solid lines are least squares fit to filtered death rate for 1875-1925 and 1925-2000. Dashed lines are estimates of 10th and 90th percentile death rates from 1925-2000. The death rate fell from 8 per million to .12 per million between 1940 and 2000. Image credit: A Brief History of Deaths from Tornadoes in the United States, Harold Brooks and Charles Doswell III.

- April 2011 had the most tornadoes of any month in U.S. history–753. The previous record was 542, set in May 2003. The previous busiest April was in 1974, with 267 tornadoes. The average number of tornadoes for the month of April during the past decade was 161, and the 30-year average for April tornadoes was 135.

- On April 27, 199 confirmed tornadoes touched down. This is the largest 1-day tornado total on record, beating the 148 recorded in 24 hours on April 3 – 4, 1974.

The year 2011 now has three of the top five tornado outbreaks on record (note, though, that reliable records for number of tornadoes only extend back in time to about the early 1990s):

- The April 25 – 28, 2011 Super tornado outbreak, with 343 tornadoes, is now the largest tornado outbreak in U.S. history. The previous record (3 days or less duration) was 148 tornadoes, set during the April 3 – 4, 1974 Super Outbreak.

- The May 22 – 27, 2011 tornado outbreak, with 180 confirmed tornadoes, ranks as the 4th largest 6-day or shorter tornado outbreak on record. A May 2003 6-day outbreak had 289 tornadoes, and a May 2004 6-day outbreak had 229 tornadoes.

- The April 14 – 16, 2011 tornado outbreak, with 177 confirmed tornadoes, ranks as the second largest tornado outbreak of three days or less duration on record, and 5th largest outbreak of six or fewer days duration.

- The May 22, 2011 Joplin, Missouri tornado killed 158 people and injured 1150, making it the deadliest U.S. tornado since 1947, and 7th deadliest in history. The $3 billion estimate of insured damage makes it the most expensive tornado in world history.

- Preliminary damage estimates from Munich Re insurance company put 2011′s insured losses due to U.S. thunderstorms and tornadoes at $25 billion, more than double the previous record set in 2010.

- The year 2011 now ranks in 3rd place behind 1974 and 1965 for greatest number of strong to violent EF-3, EF-4, and EF-5 tornadoes (Figure 5.)

Figure 5. Number of strong to violent EF-3, EF-4 and EF-5 tornadoes from 1950 to 2011, during the months March – August. The year 2011 now ranks in 3rd place behind 1974 and 1965. There is not a decades-long increasing trend in the numbers of these most dangerous of tornadoes, implying that climate change, as yet, is not having a noticeable impact on U.S. tornadoes. However, statistics of tornadoes frequency and intensity are highly uncertain. Note that beginning in 2007, NOAA switched from the F-scale to the EF-scale for rating tornado damage. Image credit: NOAA/National Climatic Data Center (2011 updates are unofficial, and were done using preliminary NWS reports.)

My last post of the year will be Friday.

Jeff Masters