Bobby Prentice
The April 26-28, 2011 "Dixie Alley Tornado Outbreak" is a contender for the largest tornado outbreak in U.S. history, perhaps even greater than the "Super Outbreak" of April 3-4, 1974 in some aspects. That outbreak resulted in 6 F5s, 24 F4s, 34 F3s, 34 F2, 33 F1s, and 19 F0s for a total of 148 tornadoes.
Based on the Grazulis definition and the SPC Storm Reports (rough log), the April 26-28 outbreak actually began with this report:
and ended 47 hours and 40 minutes later with this report:
As of May 3, 2011, the total SPC Storm Reports (rough log) tornado count for this outbreak was 388 broken up like this:
April 26, 2011.....107 (four early tornadoes in the log were not counted due to time/space constraints)
April 27, 2011.....268
April 28, 2011.......14
GRAND TOTAL=389
I know that the SPC Storm Reports (rough log) over-counts tornadoes even more since the filtering criteria standards were recently relaxed. However, even if only 40% of these reports verify, it would exceed the Super Outbreak of 1974. There is already support from NOAA for a big count:
Funny part is, the April 14-16, 2011 tornado sequence already has 155 confirmed tornadoes (according to Wikipedia) and might have beaten the Super Outbreak total (according to the Grazulis definition), but there was a 6 hour and 39 minute break between tornadoes on the morning of April 16 (between 1002Z and 1641Z).
Here's what the the outbreak looks like on the individual SPC Storm Reports maps:
Here is the preliminary tornado survey information for the outbreak from NWS Southern Region area of responsibility (NOTE: This does not include April 26 tornadoes over TX/LA/AR, April 28 tornadoes over the Carolina's and it does not include paths over NWS Central or Eastern Regions):
Tornado totals (142 of them) over NWS Southern Region (only) as of Tuesday, May 3:
[FONT="]EF-5: 2[/FONT]
[FONT="]EF-4: 12[/FONT]
[FONT="]EF-3: 20[/FONT]
[FONT="]EF-2: 39[/FONT]
[FONT="]EF-1: 40[/FONT]
[FONT="]EF-0: 29[/FONT]
Curios tidbits:
Max path width greater than or equal to one (1) mile...5
Max path width greater than or equal to one-half (0.5) miles...25
How does this outbreak rank? Grazulis's work provides some historical perspective, at least through 1995:
There have been other large outbreaks since 1995, but I haven't compiled them into a list to see how they compare to Grazulis's. According to the NOAA press release, April 3-4, 1974 (Super Outbreak) still holds the record for most tornadoes from one outbreak (148).
Thus, according to Grazulis's tornado outbreak definition, the April 26-28, 2011, "Dixie Alley Tornado Outbreak" will likely rank in 1st place all-time for total number of tornadoes, 2nd place for number of significant (EF2-EF5) tornadoes, and either 2nd or 3rd place for violent (F4/F5) tornadoes. We must wait for the final survey results to know for certain.
It would be interesting to perform a Destruction Potential Index (DPI) calculation for this outbreak as well:
THE DESTRUCTION POTENTIAL INDEX - A METHOD FOR COMPARING TORNADO DAYS by Richard L. Thompson and Michael D. Vescio
This outbreak would likely rank in 1st or 2nd place in history. Here are the DPI's for selected outbreaks (from their work):
1974 April 3 - 2647
1965 April 11 - 1632
1985 May 31 - 1338
1984 March 28 - 1301
1994 March 27 - 1292
1990 March 13 - 692
1991 April 26 - 644
1995 May 18 - 27
Significant Tornadoes 1680-1991 by Thomas P. Grazulis page 13 said:OUTBREAK...The term outbreak is used when referring to a group or family of six or more torndoes which are spawned by the same general weather system. Six tornadoes from two different thunderstorms cells, in advance of a cold front might be called a small outbreak. Six scattered tornadoes from different weather systems in three states should not be called an outbreak. This definition is from Galway (1977). Later that year, (personal conversation) he defined an outbreak of 10 ore more tornadoes from a single organized weather system. This book uses the six-tornado definition. The author has added the following addition to that definition: The end of one outbreak and the start of another is marked by a greater than six-hour lull in tornado activity, and an outbreak need not be confined to a single calendar day. Thus, if tornado activity subsides at 2 AM, and begins again at 2 PM, the Project considered that new activity to be the start of a different outbreak.
Based on the Grazulis definition and the SPC Storm Reports (rough log), the April 26-28 outbreak actually began with this report:
SPC Storm Reports - April 26 said:
and ended 47 hours and 40 minutes later with this report:
SPC Storm Reports - April 28 said:
As of May 3, 2011, the total SPC Storm Reports (rough log) tornado count for this outbreak was 388 broken up like this:
April 26, 2011.....107 (four early tornadoes in the log were not counted due to time/space constraints)
April 27, 2011.....268
April 28, 2011.......14
GRAND TOTAL=389
I know that the SPC Storm Reports (rough log) over-counts tornadoes even more since the filtering criteria standards were recently relaxed. However, even if only 40% of these reports verify, it would exceed the Super Outbreak of 1974. There is already support from NOAA for a big count:
NOAA April 2011 Tornado Information - April 26-28 said:NOAA April 2011 Tornado Information - April 26-28, 2011, Tornado Outbreak Statistics
As of May 3, NOAA's preliminary estimate is that there were 305 tornadoes during the entire outbreak from 8:00 a.m. EDT April 26 to 8:00 a.m. April 28, 2011.
Funny part is, the April 14-16, 2011 tornado sequence already has 155 confirmed tornadoes (according to Wikipedia) and might have beaten the Super Outbreak total (according to the Grazulis definition), but there was a 6 hour and 39 minute break between tornadoes on the morning of April 16 (between 1002Z and 1641Z).
Here's what the the outbreak looks like on the individual SPC Storm Reports maps:
Here is the preliminary tornado survey information for the outbreak from NWS Southern Region area of responsibility (NOTE: This does not include April 26 tornadoes over TX/LA/AR, April 28 tornadoes over the Carolina's and it does not include paths over NWS Central or Eastern Regions):
Tornado totals (142 of them) over NWS Southern Region (only) as of Tuesday, May 3:
[FONT="]EF-5: 2[/FONT]
[FONT="]EF-4: 12[/FONT]
[FONT="]EF-3: 20[/FONT]
[FONT="]EF-2: 39[/FONT]
[FONT="]EF-1: 40[/FONT]
[FONT="]EF-0: 29[/FONT]
Curios tidbits:
Max path width greater than or equal to one (1) mile...5
Max path width greater than or equal to one-half (0.5) miles...25
How does this outbreak rank? Grazulis's work provides some historical perspective, at least through 1995:
Significant Tornadoes - Update 1992-1995 by Thomas P. Grazulis said:Outbreaks with 20 or more Significant (F2-F5) Tornadoes, 1880-1995
...Date.........significant....F4/F5.......killer
.................tornadoes...tornadoes...tornadoes
Apr 03-04, 1974 ... 95 ........ 30 ........ 49 (Super)
Nov 21-23, 1992 ... 42 ......... 5 ......... 9
Apr 11-12, 1965 ... 38 ........ 19 ........ 21 (Palm Sunday 1965)
Feb 19-20, 1884 ... 37 ......... 4 ........ 28 (Enigma)
Mar 21-22, 1932 ... 36 ........ 10 ........ 27 (Deep South)
Apr 29-30, 1909 ... 35 ......... 4 ........ 24
Jun 05-06, 1916 ... 34 ......... 1 ........ 23
Apr 15-16, 1921 ... 34 ......... 1 ........ 17
May 08-09, 1927 ... 32 ......... 8 ........ 17
Mar .. 28, 1920 ... 31 ......... 8 ........ 19 (Palm Sunday 1920)
Mar 30-31, 1933 ... 30 ......... 1 ........ 16
May .. 20, 1949 ... 29 ......... 2 ......... 5
Apr 23-24, 1909 ... 29 ......... 6 ........ 16
Apr 10-11, 1979 ... 28 ......... 2 ......... 5 (Red River Valley)
Mar .. 25, 1884 ... 27 ......... 0 ........ 12
Jun 02-03, 1990 ... 27 ......... 7 ......... 4 (Lower Ohio Valley)
Mar 30-31, 1938 ... 26 ......... 3 ......... 9
Jun 07-08, 1984 ... 26 ......... 2 ......... 4 (Barneveld, WI)
Mar .. 13, 1990 ... 26 ......... 4 ......... 2
Apr 26-27, 1991 ... 26 ......... 5 ......... 5 (Andover, KS)
May 26-29, 1973 ... 26 ......... 3 ......... 8
Mar .. 16, 1942 ... 25 ......... 7 ........ 18
Mar .. 19, 1948 ... 25 ......... 3 ......... 5 (Alton-Bunker Hill-Gillespie)
May .. 05, 1960 ... 25 ......... 4 ......... 8
Mar .. 27, 1890 ... 24 ......... 6 ........ 16 (Mid Mississippi Valley)
Apr .. 30, 1924 ... 24 ......... 2 ........ 16
Apr .. 02, 1982 ... 24 ......... 4 ........ 10
Apr 15-17, 1939 ... 23 ......... 2 ........ 10
Apr .. 18, 1880 ... 22 ......... 5 ........ 14
May .. 05, 1930 ... 22 ......... 5 ......... 4
Feb 05-06, 1942 ... 22 ......... 0 ......... 9
May .. 18, 1883 ... 21 ......... 6 ........ 16
Nov .. 25, 1926 ... 21 ......... 2 ........ 14
May .. 15, 1943 ... 21 ......... 4 ......... 2
Apr .. 30, 1954 ... 21 ......... 1 ......... 2
Apr 07-08, 1980 ... 21 ......... 0 ......... 1
Mar 13-14, 1913 ... 20 ......... 3 ......... 6
May 27-28, 1917 ... 20 ......... 4 ........ 16
Apr .. 21, 1967 ... 20 ......... 4 ......... 3 (Belvidere-Oak Lawn)
May 15-16, 1968 ... 20 ......... 4 ......... 8
May .. 31, 1985 ... 20 ......... 8 ........ 10
Significant Tornadoes - Update 1992-1995 by Thomas P. Grazulis said:Outbreaks with 40 or more Recorded Tornadoes, 1880-1995
...Date............total....significant....F4/F5.......killer.....total
.................tornadoes...tornadoes...tornadoes...tornadoes...deaths
Apr 03-04, 1974 ... 148 ....... 95 ........ 30 ........ 48 ...... 315
Sep 19-23, 1967 ... 111 ....... 15 ......... 0 ......... 2 ........ 5
May 26-29, 1973 .... 99 ....... 26 ......... 3 ......... 8 ....... 22
Nov 21-23, 1992 .... 95 ....... 43 ......... 5 ......... 9 ....... 26
May 18-19, 1995 .... 80 ....... 17 ......... 2 ......... 2 ........ 4
May 11-12, 1982 .... 70 ....... 13 ......... 1 ......... 1 ........ 2
Apr 26-27, 1994 .... 67 ........ 9 ......... 1 ......... 1 ........ 3
Mar 20-21, 1976 .... 66 ....... 18 ......... 3 ......... 3 ........ 3
Jun 02-03, 1990 .... 66 ....... 27 ......... 7.......... 4 ........ 9
Jun .. 16, 1992 .... 65 ....... 12 ......... 2 ......... 1 ........ 1
Jun 26-27, 1992 .... 62 ....... 11 ......... 0 ......... 2 ........ 2
May 02-03, 1984 .... 60 ....... 15 ......... 1 ......... 1 ........ 5
Mar .. 13, 1990 .... 59 ....... 26 ......... 4 ......... 2 ........ 2
Jun 15-16, 1992 .... 58 ....... 15 ......... 2 ......... 0 ........ 0
Jun .. 08, 1993 .... 58 ........ 2 ......... 0 ......... 0 ........ 0
May .. 08, 1988 .... 57 ........ 8 ......... 0 ......... 0 ........ 0
Apr 26-27, 1991 .... 53 ....... 26 ......... 5 ......... 5 ....... 21
May 25-26, 1965 .... 51 ........ 4 ......... 0 ......... 0 ........ 0
May 04-05, 1959 .... 49 ........ 8 ......... 0 ......... 0 ........ 0
Apr 11-12, 1965 .... 48 ....... 38 ........ 19 ........ 21 ...... 256
Apr 02-03, 1982 .... 48 ....... 24 ......... 4 ........ 10 ....... 29
May 18-20, 1983 .... 48 ....... 10 ......... 0 ......... 6 ........ 6
Jan 09-10, 1975 .... 47 ........ 9 ......... 1 ......... 3 ....... 11
May 15-16, 1968 .... 46 ....... 20 ......... 4 ......... 8 ....... 74
Apr 07-09, 1980 .... 46 ........ 0 ......... 0 ......... 1 ........ 1
May .. 16, 1991 .... 46 ........ 3 ......... 0 ......... 0 ........ 0
May .. 07, 1993 .... 46 ........ 8 ......... 1 ......... 1 ........ 1
Apr .. 21, 1967 .... 45 ....... 20 ......... 4 ......... 3 ....... 58
Jun 07-08, 1984 .... 45 ....... 26 ......... 2 ......... 4 ....... 13
Nov .. 15, 1988 .... 44 ....... 13 ......... 0 ......... 3 ........ 7
Apr .. 29, 1984 .... 42 ........ 4 ......... 1 ......... 1 ........ 1
Feb 19-20, 1884 .... 41 ....... 37 ......... 4 ........ 28 ...... 167
May .. 29, 1980 .... 40 ........ 4 ......... 0 ......... 0 ........ 0
Dec .. 14, 1971 .... 40 ....... 10 ......... 0 ......... 2 ........ 2
Nov .. 07, 1995 .... 40 ........ 7 ......... 0 ......... 0 ........ 0
Significant Tornadoes 1680-1991 by Thomas P. Grazulis page 34 said:If there is a possible challenger to April 3-4, 1974 for most numerous outbreak (in the 1880-1995 period), it is May 20, 1949. Officially, only 36 tornadoes were reported that day, but that was before an organized reporting system existed. For the 1916-1949 period, tornado totals were only about one-fourth of what they are today. The newspaper headlines read "Tornado Army Hits Kansas." Clusters of small tornadoes, and a few large ones, also touched down in Oklahoma, Colorado, and Nebraska. May 20, 1949 was in the middle of a record period of activity, as significant tornadoes hit on nine consecutive days.
There have been other large outbreaks since 1995, but I haven't compiled them into a list to see how they compare to Grazulis's. According to the NOAA press release, April 3-4, 1974 (Super Outbreak) still holds the record for most tornadoes from one outbreak (148).
Thus, according to Grazulis's tornado outbreak definition, the April 26-28, 2011, "Dixie Alley Tornado Outbreak" will likely rank in 1st place all-time for total number of tornadoes, 2nd place for number of significant (EF2-EF5) tornadoes, and either 2nd or 3rd place for violent (F4/F5) tornadoes. We must wait for the final survey results to know for certain.
It would be interesting to perform a Destruction Potential Index (DPI) calculation for this outbreak as well:
THE DESTRUCTION POTENTIAL INDEX - A METHOD FOR COMPARING TORNADO DAYS by Richard L. Thompson and Michael D. Vescio
This outbreak would likely rank in 1st or 2nd place in history. Here are the DPI's for selected outbreaks (from their work):
1974 April 3 - 2647
1965 April 11 - 1632
1985 May 31 - 1338
1984 March 28 - 1301
1994 March 27 - 1292
1990 March 13 - 692
1991 April 26 - 644
1995 May 18 - 27
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