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Tropical Storms 2
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  • 1. TROPICAL STORMS - part 2 The effects of the hazard on the physical, built and human environments. GEOGRAPHY A2
  • 2. Hazards – Tropical Storms 2
    • Saffir — Simpson scale.
    • The Saffir-Simpson Hurricane Scale is a scale classifying most Western Hemisphere tropical cyclones that exceed the intensities of "tropical depressions" and "tropical storms", and thereby become hurricanes
  • 3. Hazards – Tropical Storms 2
    • The categories into which the scale divides hurricanes are distinguished by the intensities of their respective sustained winds.
  • 4. Hazards – Tropical Storms 2
    • The Saffir-Simpson Hurricane Scale is used only to describe hurricanes forming in the Atlantic Ocean and northern Pacific Ocean east of the International Date Line. Other areas label their tropical cyclones as "cyclones" and "typhoons", and use their own classification scales.
  • 5. Hazards – Tropical Storms 2
    • The scale was developed in 1969 by civil engineer Herbert Saffir and Bob Simpson
    • The U.S. National Hurricane Centre classifies hurricanes of Category 3 and above as major hurricanes
  • 6. Hazards – Tropical Storms 2
    • Effects include impact of: waves; storm surge; wind; rainfall/ flooding. Greatly influenced by vulnerability: · physical factors: intensity; distance from sea; length of time over area, etc.; · human factors: economic development; warning! evacuation; procedures etc.;· direct and indirect effects (landslides, etc.);· how to measure impact.
  • 7. Hazards – Tropical Storms 2
    • Effects
    • Tropical cyclones out at sea cause large waves, heavy rain, and high winds, disrupting international shipping and, at times, causing shipwrecks.
  • 8. Hazards – Tropical Storms 2
    • Effects on land
    • On land, strong winds can damage or destroy vehicles, buildings, bridges, and other outside objects, turning loose debris into deadly flying projectiles. The storm surge, or the increase in sea level due to the cyclone, is typically the worst effect from landfalling tropical cyclones, historically resulting in 90% of tropical cyclone deaths
  • 9. Hazards – Tropical Storms 2
    • Visit Wikipedia and investigate the Saffir-Simpson Scale
    • Produce a set of 5 boxes to explain the damage caused by hurricanes in each category.
    • Now watch the Video of a Hurricane case study
  • 10. Natural Hazards: Concepts
    • Event: the occurrence of a natural phenomenon (e.g. an earthquake, landslide, etc.)
    • Hazards: the occurrence of an event which generates risk to society. It is the interaction of people and the environment that creates a hazard (Whittow)
    • Risk: the probability of impact of an event on society (measurable in economic losses, structural damage, or lives lost)
  • 11. Natural catastrophes in 2002 US$13bn US$55bn >10,500 700 TOTAL 0 13% 18% 18% Others 37% 50% 42% 30% Flood 63% 35% 15% 39% Wind-storm 0 2% 25% 13% Tectonic Insured losses Econ. Losses Deaths Loss events Type
  • 12. Natural Hazards: Framework
    • The origin, geographical distribution, frequency of occurrence and scale of the hazard
    • Effects of the hazard on the physical, built and human environments
    • The extent of prediction and prevention
    • Responses to the hazard
    Can examine all hazards in this manner
  • 13. Hurricanes: What are they?
    • Known by a variety of names: hurricanes and tropical cyclones are the most common
    • Large scale rotating storm systems that cross a threshold of wind velocity 118km/h
    • Have a distinct season linked to their geographical distribution
  • 14. Hurricanes: Distribution
  • 15. Hurricanes: Origin
    • Hurricanes require distinct conditions to form:
      • Warm ocean location (26 deg C) to a depth of 50m – provides a heat source
      • Location above 5N and 5S: provides maximum air rotation via Coriolis force
      • Particular low level and tropospheric circulation patterns
    • These conditions apply for tropical storm formation: not all tropical storms become cyclones, and the reasons for this are still unknown
  • 16. Hurricanes: Analysis
  • 17. Hurricanes: Frequency
    • Occur within a regionally specific season (shown on distribution map)
    • Average lifespan of a cyclone is approx 7-14 days
    • Usually 70-75 tropical storms develop each year; about 50 of these will become hurricanes
  • 18. Hurricanes: Magnitude
    • Massive amounts of energy released in hurricane formation – all the nuclear weapons in the world would only power a medium sized hurricane for three hours
    • Measured using the Saffir-Simpson scale; ranks cyclones on intensity of wind and other atmospheric variables
  • 19. Hurricanes: Primary Impacts
    • High velocity wind (150-300 km/h) causes damage to structures
    • Intense rainfall (100-700mm/day) produces localised flooding and landslides
    • Low pressure surrounding the hurricane causes a tidal “storm surge” – a swelling of ocean waves up to 5m above normal height
  • 20. Hurricanes: Impact Variability
    • Intensity of hurricane (Saffir-Simpson scale, distance from sea, time over land, etc)
    • Spatial location of land fall
    • Timing of land fall
    • Length of time since last severe event
    • Population vulnerability (related to preparedness, building design, accuracy of forecasting and warning)
    • Level of society development
  • 21. Hurricanes: Prevention
    • Nothing can be done to stop the hurricane formation
    • Prevention of impact can be done through careful management, and what the National Hurricane Centre (US) term “preparedness”
    • Links careful forecasting with clear response scenarios for the emergency services and public preparation
    • Needs good forecasting: can this be done?
  • 22. Hurricanes: Prediction
    • Scale of prediction determines prediction success
    • Hurricane season usually occurs in a predictable way
    • Seasonal forecasts can be made (led by Gray et al., NHCC & Colorado) which determine how many hurricanes will form in a given season, but not necessarily when they will occur
    • Short term (days) forecasts can be made when cyclones are formed, but the variety of storm tracks make them potentially prone to failure
  • 23. Hurricane Prediction: Tracks
    • Shows a variety of tracks taken by Atlantic hurricanes in the last 5 years
    • Variability of the tracks is linked to internal factors, as well as interaction with climate oscillation patterns (e.g. ENSO, NAO)
    • Wide range of potential tracks for hurricanes makes it difficult to predict landfall sites for any individual event
  • 24. Case Study: Hurricane Isabel
  • 25. Hurricane Isabel
    • September 2003, Saffir-Simpson category 2
    • Brought storm surge flooding to upper Chesapeake Bay area, including Washington DC
    • Tropical storm conditions extended from N Carolina to Long Island NY as storm made landfall
    • Compare this to the responses and conditions surrounding Hurricane Mitch – the example in your text books
  • 26. Hurricanes: Summary
    • Tropical cyclones (hurricanes) form in specific locations and conditions
    • Magnitude and frequency are measurable via Saffir-Simpson scale, and records
    • Impacts are driven by the wind, rain and storm surge, combined with local factors to give secondary impacts
    • Prediction is limited to seasonal forecasts and short-term warnings for evacuations
    • Hazard impact is mitigated by community preparedness and emergency planning, together with economic risk assessment and insurance methods
  • 27. Tropical Storms - Prediction
    • http://www.nhc.noaa.gov/
    • This web site gives up to date data recordings of hurricanes and their path
    • http://typhoon.atmos.colostate.edu/forecasts/
    • This web site gives up to date data recordings of typhoons and their path
  • 28. Tropical Storms - Prediction
    • Since 1953, Atlantic tropical storms have been named from lists originated by the National Hurricane Centre. They are now maintained and updated by an international committee of the World Meteorological Organization. The original name lists featured only women's names. In 1979, men's names were introduced and they alternate with the women's names. Six lists are used in rotation. Thus, the 2006 list will be used again in 2012.
  • 29. Tropical Storms - Prediction
    • Andrea Barry Chantal Dean Erin Felix Gabrielle Humberto Ingrid Jerry Karen Lorenzo Melissa Noel Olga Pablo Rebekah Sebastien Tanya Van Wendy
    These are the names used during the 2007 Hurricane season. Note that they are alphabetical and, new for 2006, have been named with men’s names as well as women’s
  • 30. Tropical Storms - Prediction
    • PREDICTION IS BASED ON PAST EVIDENCE AND IS EXPRESSED AS PROBABILITIES .
    • NOAA is predicting a very high likelihood (85% chance) of an above-normal 2007 Atlantic hurricane season, a 10% chance of a near-normal season, and only a 5% chance of a below-normal season, according to a consensus of scientists at the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Centre, National Hurricane Centre, Hurricane Research Division, and Hydro meteorological Prediction Centre.
  • 31. Tropical Storms - Prediction
    • In order to predict the path of a hurricane, data from the air, from space and from the ground, are combined.
    • Then ‘best guesses are made – as shown by the video
    • Why don’t administrators enforce evacuation??? And why do they leave it late to order an evacuation???
  • 32. Tropical Storms - Prediction
    • The 2006 forecast calls for:
    • 17 named tropical storms ; an average season has 9.6.
    • 9 hurricanes compared to the average of 5.9.
    • 5 major hurricanes with winds exceeding 110 mph; average is 2.3.
    • Though these statistical predictions cannot portend when any of the storms will form or where they will go, Klotzbach, Gray and colleagues calculate an 81 percent chance that at least one major hurricane will hit the U.S. coast in 2006.
    • How the 2006 forecast compares: 20052006Avg.Tropical Storms 26179.6Hurricanes1395.9Major Hurricanes752.3
  • 33. Tropical Storms - Prediction
    • Can they be prevented?
    • See the next slide taken from ‘Tropical Storm PowerPoint 1’ about seeding
  • 34.
    • In the 1960s and 1970s, the United States government attempted to weaken hurricanes through Project Stormfury by seeding selected storms with silver iodide. It was thought that the seeding would cause supercooled water in the outer rainbands to freeze, causing the inner eyewall to collapse and thus reducing the winds.
    Hazards – Tropical Storms