1. THUNDERSTORMS Convective heavy rain accompanied by lightning and thunder Ahrens

2. Thunderstorms About 1,800 T-storms occur around the world at any instant Where do they occur the most? National Lightning Safety Institute

3. Thunderstorms Where do they occur the most?

4. Fig. 11.7 Life cycle of an ordinary thunderstorm cell

5. THUNDERSTORM CUMULUS STAGE CUMULUS STAGE REQUIRES CONTINUOUS SOURCE OF WARM MOIST AIR EACH NEW SURGE OF WARM AIR RISES HIGHER THAN THE LAST STRONG UPDRAFTS FALLING PRECIPITATION DRAGS AIR DOWN - DOWNDRAFT ENTRAINMENT

6. THUNDERSTORM MATURE STAGE SHARP COOL GUSTS AT SURFACE SIGNAL DOWNDRAFTS UPDRAFTS EXIST SIDE BY SIDE WITH DOWNDRAFTS IF CLOUD TOP REACHES TROPOPAUSE UPDRAFTS SPREAD LATERALLY - ANVIL SHAPE TOP OF ICE LADEN CIRRUS CLOUDS GUSTY WINDS, LIGHTNING, HEAVY PRECIPITATION, HAIL

7. THUNDERSTORM DISSIPATING STAGE DOWNDRAFT AND ENTRAINMENT DOMINATE NO UPDRAFT THUNDERSTORM LOSES ENERGY SOURCE

8. Fig. 11.10a Squall line associate with a cold front.

9. Fig. 11-10, p. 320 Schematic of a multicell thunderstorm. Red arrows represent the warm updraft, blue arrows the cool downdraft

10. Thunderstorms CUMULUS STAGE Dr. M. Pidwirny, Dep. of Geography, Okanagan University College ORDINARY, AIR MASS, SINGLE CELL* THUNDERSTORMS UPDRAFTS

11. Thunderstorms MATURE STAGE Dr. M. Pidwirny, Dep. of Geography, Okanagan University College ORDINARY, AIR MASS, SINGLE CELL* THUNDERSTORMS

12. Thunderstorms ORDINARY, AIR MASS, SINGLE CELL* THUNDERSTORMS MATURE STAGE NSSL

13. Thunderstorms ORDINARY, AIR MASS, SINGLE CELL* THUNDERSTORMS MATURE STAGE NSSL

14. Thunderstorms ORDINARY, AIR MASS, SINGLE CELL* THUNDERSTORMS MATURE STAGE

15. Thunderstorms ORDINARY, AIR MASS, SINGLE CELL* THUNDERSTORMS MATURE STAGE

16. Thunderstorms ORDINARY, AIR MASS, SINGLE CELL* THUNDERSTORMS DISSIPATING STAGE DOWNDRAFTS OCCUR IN THE SAME AREA AS THE UPDRAFTS DISSIPATING STAGE (DOWNDRAFTS)

17. SUPERCELL THUNDERSTORM SINGLE CELL THUNDERSTORM THAT PRODUCES DANGEROUS WEATHER REQUIRES A VERY UNSTABLE ATMOSPHERE AND STRONG VERTICAL WIND SHEAR - BOTH SPEED AND DIRECTION UNDER THE INFLUENCE OF THE STRONG WIND SHEAR THE ENTIRE THUNDERSTORM ROTATES FAVORED REGION IS THE SOUTHERN GREAT PLAINS IN THE SPRING

18. TYPE OF THUNDERSTORM SINGLE-CELL THUNDERSTORM MULTICELL THUNDERSTORM MESOSCALE CONVECTIVE C0MPLEX SUPERCELL THUNDERSTORM

19. Fig. 11-33, p. 342

20. LIGHTNING.LARGE ELECTRICAL DISCHARGE THAT RESULTS FROM RISING AND SINKING MOTIONS IN A THUNDERSTORM.SEQUENCE IS AS FOLLOWS;.CHARGE SEPARATION - REALLY DO NOT UNDERSTAND WHY.GROUND BECOMES POSITIVELY CHARGED.LIGHTNIING FORMATION BEGINS - LEADERS.LIGHTNING FLASH OCCURS

21. Fig. 11.28 Lightning formation: Charge separation.

22. Fig. 11-37, p. 346

23. Fig. 11-38, p. 346 Life cycle and path of a hailstone in a supercell thunderstorm

24. HAIL LARGE CLUMPS OR BALLS OF ICE START OF AS A SMALL ICE PARTICLE DUE TO UPDRAFT THE ICE PARTICLE DOES NOT FALL TO GROUND BUT IS RECYCLED INTO THE FREEZING PORTION OF THE THUNDERSTORM, EACH TIME IT IS TAKEN UPWARD IT ACCUMULATES MORE ICE CAN END UP AS LARGE AS A GRAPEFRUIT

25. Thunderstorms HAIL

26. Thunderstorms HAIL

27. Thunderstorms HAIL

28. Thunderstorms HAIL

29. Thunderstorms 1970 Coffeyville KA hailstone

30. Thunderstorms HAIL DAMAGE

31. Thunderstorms HAIL DAMAGE

32. Tornados Author R.T. Schindler Distributed by the Disaster Team Supercourse (www.pitt.edu/~super1)

33. Tornado History The “Tri-State Tornado” is the most violent tornado on record On March 18, 1925, the tornado formed in Missouri and traveled 219 miles across Illinois into Indiana The funnel was up to.75 miles across and traveled as fast as 73 mph. It killed approximately 635 people

34. First Tornado Forecast On March, 25 1948, Major Fawbush and Captain Miller determined that the conditions of the atmosphere just west of Tinker AFB, OK were suitable for tornado development. The first tornado forecast ever was issued. A few hours later, a tornado arrived causing significant damage to the base. However, no deaths and only a few injuries occurred because many had been warned by the tornado forecast.

35. Tornado A violently rotating column of air (vortex), hanging from a cumulonimbus cloud, with circulation that touches the surface of the earth

36. Tornado Formation

38. Supercell Storm Severe weather occurs as strong downbursts…large hail…occasional flash floods and weak to violent tornadoes Severe event almost always occur near the updraft interface typically in the rear (southwest) storm flank. Some of the supercells have the interface on the front of the southeast flank High predictability of occurrence of severe events once a storm is identified as a supercell Extremely dangerous to public Extremely dangerous to aviation

39. The Supercell Tornado forms here

40. Tornado Facts Tornados can occur almost anywhere in the world Duration: a few minutes Diameter (Avg.): 0.4 km Length of path (Avg.): 6 km Funnel can travel from 0 mph up to ~70 mph, usually travels at 30 mph 99% of all tornados in Northern Hemisphere rotate counterclockwise Texas is #1 for frequency of tornados per year Between 1950 and 1995 Texas had 5,722 recorded tornados Risk of death in a tornado in Texas: 1 in 1,054,267 Texas cost per person per year for tornados: $3.94

41. Tornado Myths A highway overpass is a safe place to take shelter under during a tornado Opening windows during a tornado will help balance the pressure between the inside and outside of the house and may prevent destruction of the structure One should seek shelter in the southwest corner of a house or basement.

42. Tornado Oddities Tornados are reported to routinely carry objects many miles and have: sucked the frogs out of a pond and dropped them on a town carried a necktie rack with 10 ties attached 40 miles carried a flour sack 110 miles from a mill Tornados also drive objects into other objects and have: Driven splinters into an iron fire hydrant Driven straw and grass into telephone poles

43. When Tornados Occur Anytime of the year- usually in the spring, summer, and fall Most tornados occur during late spring in the month of May Between the late afternoon and early evening is when most tornados are spawned The most dangerous time for formation during evening hours A typical late afternoon tornado

44. Songer http://www.pitt.edu/~super1/lecture/lec0761/005.htm

45. Where Tornados Occur Tornado Alley covers the Great Plains states

46. Tornado Wind Speed In 1971, Dr. Fujita developed a way of measuring the winds of a tornado. He reasoned that there was a link between wind speed and the damage caused by a tornado. There are 6 categories of tornados (F0 – F5)

47. F0 Category (Weak) winds (40-72) mph, little damage Damage: tree branches snapped, chimneys toppled, signs torn down

48. F3 Category (Strong) winds: (158-206) mph, severe damage Damage: most trees uprooted, trains overturned, roofs torn off, walls demolished

49. F5 Category (Violent) winds: (261- 319) mph, incredible damage; rare Damage: bark peeled off trees, houses lifted off foundations, vehicles travel greater than 100 m through the air

50. Tornado Occurrence by Category

51. Tornado Deaths by Category

53. Tornado Forecasting Meteorologists who predict tornado development analyze the current atmospheric conditions such as: air temp., barometric pressure, the locations of fronts, wind velocities, convection, etc. Probably the most useful tool a meteorologist can use to identify tornados is radar, specifically Doppler radar (WSR-88D)

54. Tornados on Radar Doppler image of a rain-wrapped tornado

55. The Life cycle of a Tornado The “Life Cycle” of a tornado consists of four distinct stages. These stages were first determined during the Union City, OK tornado of 1973 Most tornadic events are difficult to classify and may not exhibit stages that are obvious to the observer Sometimes events become unclear: one tornado weakens another appears, or single event? Tornados do not “skip” – gaps in damage path may indicate a temporary weakening in intensity

56. Beginning Stage: Tornado begins as a rotating wall cloud which quickly evolves into a funnel

57. Early Stage: Tornado funnel develops (may be transparent) and extends down from the cloud to the ground

58. Mature Stage: Tornado funnel reaches maximum width as well as maximum intensity then begins to shrink

59. Decay Stage: tornado may remain stationary and take on a ropelike appearance before dissipating

60. The Tornado Outbreak of May 3, 1999 Severe thunderstorms move into Ok, TX, Ks and spawn estimated 70 tornados, most occurred in Oklahoma In Oklahoma 40 people killed, 675 injured Damage: $1.2 billion Largest tornado outbreak in Oklahoma history 1,780 homes completely destroyed 6,550 homes damaged

62. Satellite image taken May 3, 1999 @ 645 CDT

64. View from the air of a tornado path in Central OK

65. Tornado near Amber, OK at 6:30 CDT

66. Microburst Microbursts are downdrafts from thunderstorms consisting of a narrow column of cool air traveling at high speeds which can cause damage similar to a weak tornado over a small area

67. Waterspouts A waterspout is a tornado that forms over a body of water, or a tornado that moves from land onto water

68. Storm Chasers Storm chasers are a group made up of meteorologists and scientists, as well as amateur observers who voluntarily put themselves in the path of a severe thunderstorm in order to hopefully observe a tornado and obtain photographs and scientific data.

69. Tornado Indicators A greenish colored sky associated with the thunderstorm (caused possibly by the scattering of light by particles in the sky) Mammatus clouds A sudden drop in barometric pressure Large hail of at least.75 in. diameter Strong winds > 60 mph Frequent and intense lightning A rotating wall cloud or a cloud that appears to hang from the sky A loud rumbling noise- seek shelter!

70. Mammatus clouds Green sky

71. Tornado Damage Tornados mainly cause damage by picking up something and throwing it through the air or hurling objects against something A 20-ton trailer blown off U.S. 30; it bounced 5 times A pick-up truck caught in the path of a tornado

72. Early Warning Systems The National Storm Prediction Center constantly monitors the weather and radars across the U.S. They are responsible for issuing tornado watches and warnings. Tornado Watch: a parallelogram is drawn around a 10,000 mi.^2 s area where the atmosphere seems to possess the conditions necessary for tornado development (severe thunderstorm) Tornado warning: a county has a thunderstorm which appears to have produced a tornado or someone has physically spotted a tornado, apparent funnel, or observed damage from what could be a tornado! SEEK SHELTER IMMEDIATELY!!