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PEC Departmental Safety Meeting March 2, 2010

PEC Departmental Safety Meeting March 2, 2010. Severe Weather Safety. Severe Thunderstorms. Considered severe if: Winds over 56 mph Hail 1 inch in diameter or larger Funnel cloud or tornado reported. Severe Thunderstorms. May also include: Frequent lightning

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PEC Departmental Safety Meeting March 2, 2010

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  1. PEC Departmental Safety MeetingMarch 2, 2010

  2. Severe Weather Safety

  3. Severe Thunderstorms Considered severe if: • Winds over 56 mph • Hail 1 inch in diameter or larger • Funnel cloud or tornado reported

  4. Severe Thunderstorms May also include: • Frequent lightning • Flooding and/or flash flooding • Downbursts

  5. Severe Weather Season in Alabama Two severe weather seasons in Alabama: • Primary: March through May • Secondary: November & early December

  6. Lightning Cloud-to-cloud lightning in Australia

  7. Lightning Statistics

  8. Lightning Safety • Get indoors at first sounds of thunder • If indoors, avoid: • Windows • Water sources • Telephone • Electrical appliances

  9. Lightning Safety • If caught outdoors: • Get inside a vehicle if possible • Get to lower ground • Get away from tall objects (trees, poles, other people, etc.) • Crouch down with feet together

  10. Lightning Safety • Unsafe areas include: • Canopies • Small picnic pavilions and rain shelters • Swimming pools • Open areas

  11. Lightning Safety • If planning outdoor events be prepared. • Know the local forecast • Have a weather plan ready to activate • Suspend outdoor activities until 30 minutes after last report of thunder • Victims of lightning strike do not carry a charge and first aid may be administered as soon as practical

  12. Flooding Events

  13. Flooding Events • Flooding is an excessive accumulation of water that submerges normally dry land • May include “regular” floods or flash floods • More people die annually as a result of floods than lighting, hurricanes, or tornadoes

  14. Flood vs. Flash Flood • Flood – Generally a long-term event that centers around a river, creek, or other watercourse • A flood may not peak for days after a heavy rain • May result from heavy rains upstream from the affected areas • Classified as a flood if duration is longer than 6 hours

  15. Flood vs. Flash Flood • Flash Flood – Occurs quickly when low areas cannot quickly drain after a torrential rain • May occur away from normal water courses • May occur when a water barrier (dam or levee) fails • May have little or no warning • Classified as a flash flood if duration is less than 6 hours

  16. Flood Safety • Get to high ground • Stay out of basements • Do not drive through flowing water. Water 6” deep can sweep you off your feet • Do not let children play in ditches after a rain storm

  17. Tornadoes

  18. Tornadoes • Wind speeds ranging from 40 to greater than 300 mph • Range from several yards in width to more than 2 miles • May stay on the ground for a few feet or dozens of miles

  19. Tornado Rating System • Old “F-scale” (Dr. Ted Fujita, 1971) was based solely on visual damage assessment • New “EF-rating” (Enhanced Fujita, 2007) based on damage assessment, radar measured wind speed, and structural strength of buildings damaged

  20. Tornado Rating:F4 Damage – Lots of Debris

  21. Tornado Rating:F5 Damage – Swept Clean

  22. Super Cell Thunderstorms

  23. Super Cell Thunderstorms • Usually isolated from other thunderstorms – form out ahead of the “squall line” • Characterized by a deep, rotating updraft called a mesocyclone • Responsible for generating most tornadoes

  24. Super Cell Thunderstorms

  25. Super Cell Thunderstorms

  26. Super Cell Thunderstorms

  27. Super Cell Thunderstorms

  28. Tornado Vortex Signature (TVS)Base Reflectivity “Hook Echo”

  29. TVS: Storm Relative Velocity • Green – winds moving away from radar site • Red – winds moving toward radar site

  30. TVSBirmingham, April 8, 1998

  31. TVSEnterprise, March 1, 2007

  32. Tornado Activity in the U.S

  33. Tornado Activity in the U.S.

  34. Tornado Activity in the U.S.

  35. Tornado Classification • Tornadoes and funnel clouds form from wall clouds

  36. Tornado Classification • A funnel cloud has not yet reached the ground

  37. Tornado Classification • A wedge tornado is wider than tall • Binger, OK

  38. Tornado Classification • A rope tornado near Tecumseh, OK

  39. Tornado Classification • A classic “funnel” tornado in Kansas

  40. Notable National Tornadic Events • Deadliest in U.S. History – Great Tri-state tornado of 1925 (Missouri, Illinois, Indiana) • 695 confirmed fatalities • 219 mile damage path (longest in world) • Estimated ground speed of 73 mph

  41. Notable National Tornadic Events • Super Outbreak (April 3-4, 1974) • Largest tornado outbreak in history for a 24 hour period • Extremely rare meteorological conditions • 330 confirmed fatalities

  42. Notable Alabama Tornadic Events • April 3-4, 1974 – Super Outbreak produces three F5 tornadoes (Guin, Mount Hope, Tanner) (23 killed in Guin) • April 4, 1977 – F5 tornado hits North Smithfield Subdivision near intersection of Daniel Payne Drive and I-65 (22 killed)

  43. Notable Alabama Tornadic Events • March 27 1994 – F4 “Palm Sunday Tornado” destroys Goshen United Methodist Church in Cherokee County during morning services (22 killed) • April 8 1998 – F5 tornado carves a 31 mile path through Oak Grove, Sylvan Springs, Rock Creek, Maytown, Edgewater, and McDonald Chapel (34 killed)

  44. Notable Alabama Tornadic Events • April 27, 2011– Major tornado outbreak in Southern United States. • EF4 Tornadoes common across North and Central Alabama including Tuscaloosa to Birmingham, Blountsville, Cullman, Shoal Valley, Elmore County, and Rainsville Tornadoes (all EF4) • Hackleburg hit by EF5 (first since 1998)

  45. Tornado Safety • The National Storm Prediction Center (SPC) in Norman, OK issues 1, 2, and 3 day outlooks and assigns a “risk category” • Slight Risk (4 or 5 times a year) – severe thunderstorm development expected, but relatively low coverage • Moderate Risk (1 or maybe 2 times a year) – like low risk, but with increased coverage & intensity • High Risk (rare) – used when a major outbreak is expected

  46. Tornado Safety

  47. Tornado Safety • A Tornado Watch is issued when conditions are favorable for tornado development • A Tornado Warning is issued when a tornado has been detected by radar or sighted by storm spotters • Tornadoes form quickly so you may have less than 10 minutes to execute your plan

  48. Tornado Safety • Watches are issued by the SPC for a broad area • Watches are issued on a county by county basis • Watches are intended to encourage the general public to be alert to the possibility of changing conditions

  49. Tornado Safety

  50. Tornado Safety • Warnings are issued by the local NWS office • A warning means a tornado has been detected by Doppler Radar or has been sighted by a storm spotter • Only the NWS can issue watches and warnings – local news media simply report • BHM NWS office is located at the Shelby County Airport in Calera

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