1. Thunderstorms, Hurricanes and Tornadoes

2. Thunderstorm Facts Right now there are about 2,000 thunderstorms occurring worldwide There are about 45,000 thunderstorms per day!! U.S. gets 100,000 per year!

7. Severe Thunderstorms Torrential Downpours Strong winds at greater than 58 mph Hail ¾ inch diameter (or larger) Frequent lightning

8. Severe Thunderstorm Watch Issued by National Weather Service This means that conditions are favorable for a thunderstorm Length is multiple hours.

9. Severe Thunderstorm Warning Issued By Local Weather Service Means a severe storm has been spotted by doppler radar Usually only an hour

10. Lightning

12. Types of Lightning Cloud-to-ground (CG) Intra-cloud (IC) Ribbon lightning Sheet lightning Heat lightning Ball lightning

13. Cloud-to-ground (CG) Lightning

16. Properties of a Cloud-to-ground Flash Peak current of 30 to 40 kAmps Temperatures of over 30,000  F Channel diameter of 1 to 2 cm Number of return strokes: 1 to 20 (avg ~4)

17. Properties of an Intra-cloud Flash Much more frequent than CG flashes Not well known (difficult to study)

18. Intra-cloud (IC) Lightning

21. Ribbon Lightning

24. Sheet Lightning

26. Heat Lightning

28. Ball Lightning

30. Lightning Safety Stay indoors, away from doors and windows. Do not take baths or showers. Do not use phones with cords.

31. Cars are pretty safe…

32. Thunder

33. How Far Away Was That Lightning? When you see the flash, start counting seconds. When you hear the thunder, stop counting. Every 5 seconds is equal to 1 mile.

34. Tornadoes

36. F-Scale F0 – Light damage F1 – Moderate damage F2 – Considerable damage F3 – Severe damage F4 – Devastating damage F5 – Incredible damage (Auntie Em!)

37. Tornadoes in Pennsylvania From 1950 - 2005 there were: – 694 tornadoes in Pennsylvania 22 F4 2 F5 –27 tornadoes in Lancaster County 1 F3 No F4 or F5

40. Tornado Watch Conditions are favorable for a tornado to form

41. Tornado Warning A tornado has formed.

42. Tornado Safety Get indoors and stay there Stay away from doors and windows Get to lowest level possible Don’t get near things that can fall on you

43. Hurricanes

44. Formation Regions

45. Typical Paths

46. When to expect Hurricane season is June through November Peak is in September

47. Formation of Hurricanes Tropical Depression Tropical Storm Hurricane

48. Tropical Depression Cluster of organized thunderstorms Not very compact Sustained winds of at least 30 mph Given a number

49. Tropical Storm Winds above 39 mph Given a name More organized If hits land, most damage caused is by rainfall.

50. Hurricane Winds over 74 mph Well defined center of circulation Eye Wall Damage from includes: –Wind –Storm surge –Rain

51. Pressure in hurricane A way to tell strength of hurricane is by its pressure Measured in millibars (mb) Higher pressures are weak, lower are stronger

52. Naming System A list of names from A-W (excluding Q) Alternate from male to female 6 lists, repeated in cycle Big name storms replaced

53. Saffir-Simpson Scale Designed by Herbert Saffir and Bob Simpson Divides hurricanes into categories based on maximum sustained winds.

54. Category 1 Winds- 74-95 mph Storm Surge- 4-5 ft. Pressure- 986mb Damage- mobile homes, trees, minor costal flooding

55. Category 2 Winds- 96-110 mph Storm surge- 6-8 ft. Pressure- 965- 979 mb Damage- Some roof and window. Damage to piers on coast. Small crafts. vegetation

56. Category 3 Winds- 111-130 mph Storm surge- 9-12 ft. Pressure- 945-964 mb Damage- structure damage to homes and buildings. Mobile homes destroying. Major coastal flooding with a potential for inland flooding.

57. Category 4 Winds 131-155 mph Storm surge- 13-18 ft. Pressure- 920-944 mb Damage- Complete roof damage. Major erosion to beaches. Further inland flooding.

58. Category 5 Winds- Greater than 156 mph Storm surge- over 19 ft. Pressure- less than 920 mb Damage- Roofs torn off, buildings collapse, major inland flooding.

59. Hurricane Watch A hurricane poses a possible threat within the next 36 hours

60. Hurricane Warning Hurricane conditions expected within 24 hours

61. Most Damaging Storms 1) Katrina (2005)- 75 billion 2)Andrew (1992) 34 billion 3)Charley (2004)- 14 billion 4) Ivan (2004)- 13 billion 5) Wilma (2005)- 12 billion..9) Agnes 1972 8.6 billion

62. Hurricane Safety Best plan is to evacuate –Towns have voluntary evacuation during a watch, and some switch to mandatory during a warning. Plan early in advance

63. IF you choose to stay Board all windows Prepare Flashlights, avoid candles Stay tuned to radio Stay indoors