1. THUNDERSTORMS

2. THUNDERSTORMS CUMULUS STAGE
As the sun heats the land, the warm humid air rises & condenses forming a cumulus cloud

3. MATURE STAGE
Updrafts pull in more “fuel” or warm air & moisture forms water droplets (rain/hail)
Once these droplets get big enough, gravity pulls them back down creating downdrafts

4. Mature, ordinary cell thunderstorm with anvil head

5. DISSIPATING STAGE
Updrafts weaken as they cool and downdrafts release the moisture that has built up

6. Review of Stages:
Developing (cumulus), mature and
dissipating

8. Lightning Source of lightning: the cumulonimbus cloud
Collisions between super-cooled cloud particles, water droplets, and hail cause clouds to become charged
Most of the base of the cumulonimbus cloud
becomes negatively charged – the rest becomes
positively charged
These charged particles connect with the ground and creates lightning
The thunder is the air clapping back together after the lightning slices through it!

10. Development
of lightning

11. Distribution of lightning strikes
[insert fig 11-23]

13. Four types
of cloud-
ground
lightning
Most
common

15. TORNADOES Area low pressure storm that usually forms over land
800 tornadoes are reported in the U.S. per year on average
Tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground… the rotating column of air is called the vortex
Vortex is only visible when debris and dirt gets carried up with the winds

16. When & Where do they occur?
Tornado Alley – Combination of cold dry air and warm moist air meet in the middle of the US
They occur mostly during the spring and summer (April-June)
They usually occur during the late afternoon and early evening.

17. Global tornado frequency
[insert fig 11-32] 17

18. How long is a tornado usually on the ground?
Can range from a few seconds to several hours but 5 minutes is average
How fast do tornadoes move?
Movement can range from
virtually stationary to more
than 60 miles per hour but average is miles per hour.

24. Develop over warm waters Smaller and weaker than tornadoes
Waterspouts
Similar to tornadoes
Develop over warm waters
Smaller and weaker than tornadoes 24

25. Watch—means conditions are favorable for tornado to develop
Warning—means that tornado has been spotted

26. THE WIND!
Take a look at this piece of wood that was driven into the palm tree.

27. LOOK AT
THESE

28. MEASURING DESTRUCTION
The Enhanced Fujita Scale rates tornadoes based on the amount and type of wind damage produced.

29. [insert table 11-2] 29

30. EF-0. Light damage
Wind 65 to 85 mph. Causes some damage to siding and shingles

31. EF-1. Moderate damage Wind 86 to 110 mph. Considerable roof damage
EF-1. Moderate damage Wind 86 to 110 mph. Considerable roof damage. Winds can uproot trees and overturn single-wide mobile homes. Flagpoles bend.

32. EF-2. Considerable damage Wind 111 to 135 mph
EF-2. Considerable damage Wind 111 to 135 mph. Most single-wide mobile homes destroyed. Permanent homes can shift off foundation. Flagpoles collapse. Softwood trees debarked.

33. EF-3. Severe damage Wind 136 to 165 mph. Hardwood trees debarked
EF-3. Severe damage Wind 136 to 165 mph. Hardwood trees debarked. All but small portions of houses destroyed.

34. EF-4. Devastating damage Wind 166 to 200 mph
EF-4. Devastating damage Wind 166 to 200 mph. Complete destruction of well-built residences and large sections of school buildings

35. EF-5. Incredible damage.
Wind mph. Significant structural deformation of mid- and high rise buildings.
Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 yards
May 25th, 2008
Catastrophic damage was reported in Parkersburg as much of the town was destroyed, with reports of flattened houses and debarked trees. Six people were killed in Parkersburg and at least two fatalities were reported where a housing development was destroyed. At least 70 people were injured

36. At 9:45 p. m. on May 4, 2007, Greensburg was hit by an EF5 tornado
At 9:45 p.m. on May 4, 2007, Greensburg was hit by an EF5 tornado. The tornado was estimated to be 1.7 miles (2.7 km) in width and traveled for nearly 22 miles (35 km). Ninety-five percent of the city was confirmed to be destroyed, with the other five percent being severely damaged. The National Weather Service estimated winds of the tornado to reach 205 mph (330 km/h). This was the first tornado to ever be rated EF5 since the update of the Fujita scale.

37. HURRICANES
Low pressure systems that form over warm, tropical waters near the equator
Most form between 5 and 20 degrees north latitude — they almost never form in the South Atlantic

38. Different names are given to hurricanes depending on where they form
Atlantic—we call them hurricanes
Pacific—they are called typhoons
3. Indian Ocean—they are called cyclones

39. Ok, So What Exactly Is a Hurricane?
A hurricane can best be described as a huge tropical storm (up to 600 miles in diameter)!
Winds can be up to 200 mph!
Storms usually don’t last for more than 7-10 days.
It moves across the ocean at around mph…not too fast really!
Arrows indicate “feeder bands” or “rain bands”
The winds are the strongest around the eye wall. The eye of the storm is usually about 20 miles in diameter. Within the eye, winds are calm and the weather is great. Strongest winds are on the right side, heaviest rain is usually on the left side.

40. Mature hurricanes average about 350 miles across
They have the lowest barometric pressures ever recorded with any storm (905 millibars is lowest recorded)
These huge air pressure differences is what creates the rapid, inward spiraling of winds

41. What Does a Hurricane Need in Order to Develop?
A hurricane needs warm water, time to grow, and favorable upper level winds in the troposphere. If the winds are too strong, they will blow the hurricane apart – we call that wind shear!

42. THE END OF A HURRICANE
When a hurricane travels over land or cold water, its energy source (warm water) is gone and the storm weakens, quickly dying.

43. CATEGORY WIND SPEED STORM SURGE DAMAGE
MEASURING DESTRUCTION
We use the Saffir-Simpson scale to rank hurricane intensities
Saffir-Simpson Scale
CATEGORY
WIND SPEED
STORM SURGE
DAMAGE 1
74-95 mph
4-5 feet
Minimal 2
mph
6-8 feet
Moderate 3
mph
9-12 feet
Extensive 4
mph
13-18
Extreme 5
Greater than 155
Greater than 18
Catastrophic
Video Clip on Wind Tunnel

44. Stage 1 – Tropical Depression(Wave)
Evolution of Hurricane Development -- Stages
Stage 1 – Tropical Depression(Wave)
Usually has begun its life off of the west coast of Africa in the ITCZ. Tropical depressions have winds of less than 39mph, and are not given a name.
Lacks structure – no well developed feeder bands or eye

45. Stage 2 – Tropical Storm
At this point, the tropical storm is beginning to develop some serious structure. Winds range from mph. In the Atlantic, storms are given a name when they reach this stage.
Feeder bands are beginning to develop – you can see the center of the low pressure system more easily. Eye and eye wall still not well formed.

46. Stage 3 – Category 1 Hurricane
Winds range from mph.
Well developed feeder bands. An eye begins to form (although it is covered in clouds). Storm is tightening around center.

47. Stage 4 – Category 2 Hurricane
Winds range from mph.
Well developed feeder bands. An eye and eye wall are usually very well formed. Storm continues to tighten around center.

48. Stage 5 – Category 3 Hurricane
Winds range from mph.
Now considered a “Major Storm”. Intense flooding and building damage will occur to most areas on the coast. Further inland, the damage will still be substantial.

49. Stage 6 – Category 4 Hurricane
Winds range from mph.
Shrubs, signs and trees can be blown down. COMPLETE DESTRUCTION of mobile homes is possible. Extensive damage to doors and windows. Major damage to lower floors of structures near the coast.

50. Stage 7 – Category 5 Hurricane
Winds greater than 156 mph!
Complete roof failure on many residential and industrial buildings. Some complete building failures with small utility buildings blown over or away.
Massive evacuation of residential areas on low ground within 5-10 miles of the coastline maybe required.

51. Category 5 Status includes:
Hurricane Wilma (October 2005) -- Gulf of Mexico, Yucatan Peninsula, Mexico, Cuba, and Southern Florida
Hurricane Rita (September 2005) -- hit Texas, Louisiana
Hurricane Katrina (August 2005) -- hit southern Louisiana, Mississippi and Alabama
Hurricane Isabel (September 2003) -- hit North Carolina, Maryland, Delaware, Virginia, and Washington, D.C.
Hurricane Andrew (August 1992)-- hit southeastern Florida and southeastern Louisiana
Hurricane Camille (August 1969) -- hit Mississippi, SE Louisiana, and Virginia

52. STORM SURGE ACCOUNTS FOR 90% OF HURRICANE-CAUSED DEATHS

53. HURRICANE SEASON
Occurs from June through November
Most hurricanes form during the late summer months because the ocean is still retaining heat from the warmer earlier months

54. What kind of damage are we talkin’ about here?
Might want to take the detour…

55. Aftermath…

56. Aftermath…