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THUNDERSTORMS

THUNDERSTORMS. Convective heavy rain accompanied by lightning and thunder. Ahrens. Thunderstorms. About 1,800 T-storms occur around the world at any instant Where do they occur the most?. National Lightning Safety Institute. Thunderstorms. Where do they occur the most?.

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THUNDERSTORMS

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  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. Life cycle of an ordinary thunderstorm cell Fig. 11.7

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

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

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

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

  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. Lightning formation: Charge separation. Fig. 11.28

  22. Fig. 11-37, p. 346

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

  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

  37. 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

  38. The Supercell Tornado forms here

  39. 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

  40. 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.

  41. 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

  42. 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

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

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

  45. 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)

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

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

  48. 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

  49. Tornado Occurrence by Category

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