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Tornadoes 2011 – Superoutbreak 2 Dr. Greg Forbes Severe Weather Expert The Weather Channel 2011 NWA Teachers Weather Workshop Birmingham, AL October 17,

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Presentation on theme: "Tornadoes 2011 – Superoutbreak 2 Dr. Greg Forbes Severe Weather Expert The Weather Channel 2011 NWA Teachers Weather Workshop Birmingham, AL October 17,"— Presentation transcript:

1 Tornadoes 2011 – Superoutbreak 2 Dr. Greg Forbes Severe Weather Expert The Weather Channel 2011 NWA Teachers Weather Workshop Birmingham, AL October 17, 2011

2 Radar echo of the SUPERCELL (rotating) thunderstorm, spawning the EF4 tornado at Tuscaloosa AL Lavender-colored ball is due to debris tossed aloft in the tornado Strong radar return used to simulate the tornado in 3D

3 Personal Damage Observations from April 27 I flew in a helicopter over part of the Tuscaloosa tornado path and crossed part of another tornado path farther east I thought some of the structural damage in Tuscaloosa would have been F5 in the past (original Fujita Scale) The trees northeast of Tuscaloosa often fell inward TOWARD the tornado from the northeast; inflow winds before the strongest southwest winds arrived!

4 Tuscaloosa, AL Before April 27 After April 27 EF-4 EF-0 EF-1 EF-1 to 2 EF-3 Tornadoes are rated based upon worst damage Now using the Enhanced Fujita (EF) Scale

5 ^ ^ ^ Original F-Scale F Enhanced Fujita Scale EF Engineers said F3 and higher wind estimates were usually too high. Homes not built that strongly.

6 Enhanced Fujita Scale for Houses Houses have Achilles heels that cause them to fail in winds weaker than 200 mph EF4 EF3 EF2 EF0 EF1

7 Wind speeds are ESTIMATED afterwards based upon surveying damage using Enhanced Fujita Scale 87% of tornadoes are Weak (EF0 and EF1) Strong (EF2 and EF3) and Violent (EF4 and EF5) tornadoes are less common but cause 92% of deaths Death rate is 50 to 100% greater at night Better initial home construction could keep EF1 from meaning totally destroyed Need more in-home shelters to safe lives

8 Tuscaloosa AL Apartment Complex – southeast corner two-story apartments leveled (EF4, could have been F5) apartment debris toward northeast home debris down embankment toward northwest (inflow) EF3 trees converge trees down from northeast (left-side inflow) EF4+ EF0 EF2 -3 EF0 - 1

9 Railroad bridge destroyed outside Tuscaloosa – no EF-Scale guidance on bridges

10 NWS-BMX Hackleburg AL EF5 – brick home disintegrated

11 I never thought Id see so many deaths from tornadoes as in 2011 Deadliest Known Tornado Years in USA 1.1925 – 794 2.1936 – 552 3.1917 – 551 4.2011 – 546 (+ ?) 5.1927 – 540 6.1896 – 537 2011 had the deadliest tornadoes since 1957: Joplin MO (159) Hackleburg AL (72) Tuscaloosa AL (63)

12 April 2011 Tornado Outbreaks: April 2011 Tornado Tally: - 748 tornadoes - shattered old April record (267 in 1974) -broke record for any month (542 in May 2003) 2011 Tornado Tally: -about 1371 tornadoes through June 30 (record 1304 in 2008) - 546 killed from 57 killer tornadoes (most since 1936) - deadliest tornado (Joplin, MO on May 22 killed 159) since 1947 (Woodard, OK, 181 killed) - Largest tornado outbreak on record (about 293 tornadoes, 4/26-28)

13 Factors in Tornado Formation Instability – needed to get intense thunder- storms to form; with low cloud bases Favorable winds and wind shear – winds turn clockwise and increase speed in lowest 3000 feet source of damaging winds, rotation A meteorological trigger: upper-air trough or jet streak, low-level convergence or front, etc. to help storms break through initial inhibition

14 PRIME TORNADO AREA – Large-scale factors

15 Supercell Thunderstorms: Strong Instability and Shear (component) (Component)

16 Tail Cloud, Independence, KS, 7/8/2008 – Dale Reynolds TailWall cloud

17 Classic supercell thunderstorm The worst tornadoes come from supercells Thunderstorms that have large, long-lived rotating updrafts

18 Overshooting top – where the updraft reaches storm top anvil

19 Very anomalous, persistent weather pattern in April 2011 Very warm from Ohio Valley to South Strong and persistent jet stream and trough

20 2011 Superoutbreak (AL portion) Joplin MO tornado – May 22, EF5, 159+ killed - Deadliest tornado in USA since 1947 April 26-28, 2011 Tornado Outbreak Records (any outbreak) 293 tornadoes 316 deaths (second to 1925) 2900+ miles of path 67 tornadoes 400+ yds wide 21 states hit (numbers preliminary) Ringgold, GA EF-4 Philadelphia EF-5 Rainsville EF-5 Rainsville AL EF5 Smithville MS EF5 Hackleburg- Phil Campbell AL EF5 MS EF5

21 Preliminary Comparison of Superoutbreaks – 1974 vs 2011 (24 hours each) * * * * Forbes Impact Index (100 max) 68.86 68.53 (next in line, 37.46)

22 Until 2011, the benchmark tornado outbreak was the Superoutbreak of April 3-4, 1974 I studied the 1974 Tornado Superoutbreak with Dr. Fujita 148 tornadoes 24 hours Multiple suction vortices

23 Yellow – Thunderstorms expected Red – Severe thunderstorms possible day of Yazoo City, MS EF4 Tornado Apr 24, 2010 I developed TORCON in 2009 to help inform people of tornado risk

24 TORCON – TORNADO CONDITIONS INDEX Scale of 0 to 10 (First 10 – north AL, 4/27/2011) Multiply by 10 to get approximate probability of a tornado within 50 miles (e.g., 5 50%) Based upon forecasts of weather conditions needed for tornado formation and how well they may come together Combines numerical model guidance, human expertise

25 Supercell Structure Rear-flank downdraft

26 Tornado families A supercell thunderstorm often spawns a sequence of tornadoes called a tornado family The gaps between tornadoes are usually downdraft-induced

27 So the storm-scale downdraft can create (and destroy) a tornado Classic Mesocyclone Cycling tornado family Relates to Rear-Flank Downdraft Fujita and Forbes – tornado turns and hook echo evolution during Superoutbreak

28 There Are Lots of Unknowns, Issues As few as 10% of supercells produce tornadoes NWS Tornado Warning False Alarm Rate (FAR) is about 75% (2008) NWS Tornado Warning Probability of Detection (POD) about 72% (2008) NWS Tornado Warning Lead Time 13+ min (2008) Radar beam wider than tornado, overshoots sub- cloud-base tornado at distances from radar Improvements if more radars? Need more efficient warning system for people to receive warnings

29 Poor NEXRAD coverage below 1 km AGL degraded tornado detection Good meso detection Denser network of low-power low-cost radars on cell towers? McLaughlin et al 2009: BAMS 90(12), 1797-1817 3 km coverage 1 km coverage

30 Recent Extreme Events – Global Warming? Feb 10, 2009 – Strongest and deadliest Feb OK tornado on record Jan 7, 2008 – 2 WI tornadoes (Jan - only one previously) Jan 7, 2008 – northern IL tornado (Jan – only one other since 1950) Jan 10, 2008 – EF1 tornado near Vancouver, WA (Jan – only 2 previously since 1950) Feb 5-6, 2008 Largest Feb outbreak on record; mid-South Oct 18, 2007 – unprecedented killer tornado, northern MI Dec 1, 2006 – 1 st PA December tornadoes Nov 1, 2000 – tornadoes near Bismarck, ND; farthest north so late in year Mar 11-13, 2006 – largest March outbreak Sept 22, 2006 – largest non-tropical outbreak Dec 29, 2006 – unprecedented TX Dec outbreak Rare/Unprecedented Northern and Cold Season Events

31 Severe Weather and Global Warming Trapp et al, 2007: Proc. Natl. Acad. Sci. 104(50), 19719-19723 MAMJJA Difference in climate model parameters, 2072-2099 vs 1962-1989, RegCM3 NDSEV = # Severe T-storm days, when CAPEx(0-6 km shear) at least 10,000 CAPE increases – warmer, moister, more unstable Surface specific humidity increases 0-6 km shear mostly decreases 2 to 3 more days with severe thunderstorms NSDEV increases, up to 100% in South and East Different results for different climate models


33 Strong upper trough and upper-level jet streak Approaching frontal system; Warm moist air off Gulf of Mexico Weather Maps, morning April 27, 2011

34 Tornado Winds are Estimated from Damage Replaced by Enhanced Fujita EF Scale, 2/1/2007 (Original)

35 Fujita Scale (F0 to F5) F0 Damage, EF0 damage

36 Milestone Tap, Utica IL April 20, 2004 F3 to F4 EF3

37 EF3, Wheatland, WI, 1/7/2008 – Elizabeth Moore

38 Saved by a safe room, Wheatland, WI EF3, 1/7/2008 – Elizabeth Moore

39 Fujita Scale F5 Damage in past, now often EF4

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