WILD WEATHER!!

1. WILD WEATHER!!

2. Are hurricanes becoming more intense??? • 2005 – worst hurricane season on record – broke the 2004 record, the previous worst season on record • The number of category 4 and 5 storms between 1990 and 2006 increased dramatically compared with the interval between 1975 and 1989. • The power of the most recent hurricanes (measured by wind speed and duration) has increased by 50% since 1970!

3. Nearly all of the most destructive hurricane seasons on record have occurred in the past 10 years, many of the years in the 2000s near record levels of major hurricanes. • Seasons with most major hurricanes: 2005, 1999, 1996, 1994 – made top 5 list • Seasons with the most named tropical storms in the Atlantic – 1995, 2000, 2001, 2003, 2004, 2005, 2007, 2008 – made top ten list • 1933 and 1936 are the only 2 years on the list before 1969

4. 2005 – worst hurricane season ever! • 28 large officially named tropical storms • 15 hurricanes • 5 category 4 (wind speed > 131 mph!) • 4 category 5 (wind speed > 155 mph!) • June – tropical storms Arlene and Brett and Hurricane Cindy – Louisiana, Mississippi • July 5 – Hurricane Dennis – Category 4 hit Cuba, Haiti, Florida

5. July 11 – Hurricane Emily – Category 5 – SE Mexico • August – Tropical Storms Franklin, Gert, Harvey, Hurricane Irene, Tropical Storm Jose • Then – Aug. 29 – Hurricane Katrina! • September – Hurricane Maria – reached Iceland and Norway; Hurricanes Nate and Ophelia – N. Carolina; Hurricane Rita – Sept. 21, category 5 hit Florida keys • October – Hurricane Stan – Mexico, Hurricane Tammy - Forida

6. Hurricane Vince – Spain (first hurricane in that region since 1942!) • October 17 – Hurricane Wilma – strongest hurricane on record in Atlantic – wind speeds > 255 mph, highest pressure ever recorded – most damaging storm to hit Mexico in history

7. The standard system for naming Atlantic hurricanes uses 21 names in alphabetical order. Wilma was the 21st and last named hurricane. However, the season was not over, so Greek letters were used for the first time! • After 2005, the World Meteorological Organization retired 5 names from rotating list of tropical storms: Dennis, Katrina, Rita, Stan and Wilma • (see p. 162 of text)

8. Can we be certain that hurricanes have become worse in recent years? • Lack of detailed historical record • There are almost no reliable historical records of hurricanes before 1900 • The data for oceanic temperatures and hurricane velocities do not go back far enough, so it is hard to establish past correlation

9. Greenhouse Effect and Global Warming • Is global warming affecting the occurrence of hurricanes?

10. CYCLONIC STORMS • Hurricanes – Atlantic and Eastern Pacific • Typhoons – Pacific Ocean • Cyclones – India Ocean • These storms occur in a belt just above and below the equator, but not at the equator. This is because the prevailing winds at the equator do not form a strong spiraling pattern that promotes the spiral (“cyclonic”) flow of hurricanes

11. All of these tropical storms arise from similar forces: excess heat in the ocean

12. Hurricanes! • Hurricane – large rotating storm of tropical origin that has sustained winds of at least 119 km/hr (74 mph) • The air pressure at the center of a hurricane is very low • Hurricanes gets their energy from the heat of surface ocean water

13. Hurricanes have a spiral structure

14. Katrina

15. Sandy

16. Irene

17. Typhoon Haiyan

18. At the hurricane’s outer edge, rain and wind are comparatively mild • They increase as the winds spiral in toward the low-pressure area at the hurricane’s center – aka – The EYE! • The eye wall – ring of violent thunderstorms that surround the eye. The strongest winds and heaviest rains are found here • When the eye wall passes over an area, great damage results • Inside the eye, winds are mild and there is no rain

19. How do hurricanes form? • For a hurricane to form – there must be supply of warm, moist air for a long period of time • The surface temperature of the ocean must be at least 27 C or 80 F • Remember water cycle – water that evaporates from the ocean condenses within storm clouds, releasing large amounts of heat. This heat fuels the gradual development of a hurricane

20. So, once the surface temp is 80 F, conditions are right for a tropical storm • If the air above the ocean is also warm, humid and unstable and there are no strong upper-level winds to move the heat away, a tropical storm develops • Typically there is also a large area of low pressure over the tropical Atlantic, Pacific or Indian Oceans

21. This low pressure zone begins with a series of small, disorganized thunderstorms with weak surface winds. This is known as a tropical disturbance. • If the surface winds become stronger and better organized, they soon spiral around the area of low pressure in cyclonic fashion around a central core, forming a tropical depression

22. Hurricane formation begins in the tropics with a mild atmospheric disturbance that causes humid air to rise. As the air rises, it cools and water condenses, releasing heat • More humid air flows in at the surface to replace the rising air, and as this humid air rises, more water condenses and releases heat • This process continues as long as humid air is available at the surface and air is leaving the disturbance at higher levels

23. Because hurricanes rely on the transfer of heat from the ocean, they form only when surface ocean waters are sufficiently warm, and they weaken as soon as they make landfall or move over cold ocean water • Surface ocean water is warmest in summer and early fall, so hurricane season in US is usually June – November. • Throughout their development, hurricanes are steered by global wind patterns. Hurricanes that form in the Atlantic Ocean north of the equator initially move west or north west, but often curve north and eventually head east. • However, actual path of hurricanes varies a lot!

24. http://www.bing.com/videos/search?q=video+clips+of+hurricane+katrina&FORM=VIRE7#view=detail&mid=51060739B0BE2D07F62151060739B0BE2D07F621http://www.bing.com/videos/search?q=video+clips+of+hurricane+katrina&FORM=VIRE7#view=detail&mid=51060739B0BE2D07F62151060739B0BE2D07F621 • Katrina 2 min video clip • http://www.youtube.com/watch?v=afe2TF6yi5Q • Path video from sandy – 36 sec

25. Classification of Tropical Storms Scientists classify tropical disturbances according to speed of strongest winds • Tropical depression: wind speeds up to 61 km/hr (37.9 mph) • Tropical storm – 61 – 119 km/hr (38 – 74 mph) • Hurricane – wind speeds > 119 km/hr (74 mph)

26. Effects of Hurricanes • Storm surge- forms when the hurricane piles up water along the shore and then blows it inland • Storm surges much more damaging when they happen during high tide (Sandy!) • Storm surges can raise sea level several meters higher than normal • Winds also create huge waves

27. Safety tips?

28. Listen to updates – before and during • Secure loose objects outside - before • Have a flood-free evacuation route planned- before • Stay indoors, away from windows- during • Beware of downed wires, flooded areas, unsafe roads, broken gas lines - after

29. Watches and Warnings • Watch – when hurricane expected to arrive in a community within 24 – 36 hours • Warning – when hurricane expected to arrive 24 hours or less

30. Saffir-Simpson Hurricane Scale

31. Refer to the list you compiled yesterday of the 10 worst storms in history. • Pick one – describe it in detail! • Where • When • Category, wind speed, height of storm surge • Damages to homes, buildings, infrastructure • Injury, death, socioeconomic impact • Recovery/relief • Organize your information into a poster

32. For you to do……..Choose one of the following: • Typhoon Nina • Cyclone Nargis • 1900 Hurricane in Galveston, TX • SupertyphoonHaiyan • Hurricane Wilma • Hurricane Andrew • Hurricane Camille

33. Research a cyclonic storm (from choices listed) • Describe where and when it took place • Was there any warning? • What category storm? • Include wind speed, height of storm surge • Effects – damages to infrastructure and homes, injuries, lives lost, socioeconomic issues • Recovery/relief effort • At least 2 sources • Pictures and video clip • Also use info presented in your text book! (that can be a source)