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Tornadoes 2011 – Superoutbreak 2

Tornadoes 2011 – Superoutbreak 2. Dr. Greg Forbes Severe Weather Expert The Weather Channel. 2011 NWA Teacher’s Weather Workshop Birmingham, AL October 17, 2011. Radar echo of the SUPERCELL (rotating) thunderstorm, spawning the EF4 tornado at Tuscaloosa AL.

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Tornadoes 2011 – Superoutbreak 2

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  1. Tornadoes 2011 – Superoutbreak 2 Dr. Greg Forbes Severe Weather Expert The Weather Channel 2011 NWA Teacher’s 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  EF-1  EF-0 Before April 27 EF-4 EF-3  EF-1 to 2 Tornadoes are rated based upon worst damage After April 27 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 EF0 EF1 EF2 EF2 EF3 EF3 EF4

  7. Wind speeds are ESTIMATED afterwards based upon surveying damage using Enhanced Fujita Scale • Better initial home construction could • keep EF1 from meaning “totally destroyed” • Need more in-home shelters to safe lives • 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

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

  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 I’d see so many deaths from tornadoes as in 2011 Deadliest Known Tornado Years in USA • 1925 – 794 • 1936 – 552 • 1917 – 551 • 2011 – 546 (+ ?) • 1927 – 540 • 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 293tornadoes, 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 Wall cloud Tail Cloud, Independence, KS, 7/8/2008 – Dale Reynolds

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

  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) Rainsville AL EF5 • 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) Smithville MS EF5 Hackleburg- Phil Campbell AL EF5 Joplin MO tornado – May 22, EF5, 159+ killed - Deadliest tornado in USA since 1947  Ringgold, GA EF-4  Rainsville EF-5 MS EF5 Philadelphia EF-5

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

  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. Rear-flank downdraft Supercell Structure

  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 Fujita and Forbes – tornado turns and hook echo evolution during Superoutbreak “Classic” Mesocyclone Cycling  tornado family Relates to Rear-Flank Downdraft

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

  30. Recent Extreme Events – Global Warming? Rare/Unprecedented Northern and Cold Season Events • 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 – 1st 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

  31. Severe Weather and Global Warming MAM JJA Trapp et al, 2007: Proc. Nat’l. Acad. Sci. 104(50), 19719-19723 CAPE increases – warmer, moister, more unstable Difference in climate model parameters, 2072-2099 vs 1962-1989, RegCM3 Surface specific humidity increases Different results for different climate models 0-6 km shear mostly decreases NDSEV = # Severe T-storm days, when CAPEx(0-6 km shear) at least 10,000 2 to 3 more days with severe thunderstorms NSDEV increases, up to 100% in South and East

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

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

  34. Fujita Scale (F0 to F5) • F0 Damage, EF0 damage

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

  36. EF3, Wheatland, WI, 1/7/2008 – Elizabeth Moore

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

  38. Fujita Scale • F5 Damage in past, now often EF4

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