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Tropical storms

Tropical storms Classification Development Trajectories Forecasting Hazards Future prospects Tropical disturbances, etc. Saffir-Simpson scale Spawning areas for tropical storms (SST >27°C) Tropical storm genesis: convergence behind an easterly wave

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Tropical storms

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  1. Tropical storms Classification Development Trajectories Forecasting Hazards Future prospects

  2. Tropical disturbances, etc.

  3. Saffir-Simpson scale

  4. Spawning areas for tropical storms (SST >27°C)

  5. Tropical storm genesis:convergence behind an easterly wave In a typical hurricane season some 60 easterly waves develop in the North Atlantic. Only about 1 wave in 5 becomes a tropical depression. Strong upper level troughs and westerly winds commonly suppress hurricane formation

  6. Mature hurricane Development fostered by release of heat from condensed water in bands of clouds around the tropical storm centre more rapid convergence and updrafts. This +ve feedback leads to intensification and hurricane formation.

  7. Structure of Hurricane Gilbert(Doppler radar cross-section )

  8. The Atlantic hurricane season(Dr. William Gray @ Colorado State U.) Strong Azores High inhibits hurricanes Strong El Niño suppresses hurricanes (but 1998?) Wet springs inhibit hurricanes Strong stratospheric easterlies suppress hurricanes Low SST’s inhibits hurricanes

  9. Atlantic hurricanes(1995 season)

  10. Tracks of typhoons affecting the China Sea region

  11. Tracks of cyclones in the northern Indian Ocean

  12. Effects of travelling high and low pressure systems on hurricane paths

  13. Hurricane Andrew (1992)

  14. Hurricanes - examples of unpredictability

  15. Forecasting • NHC (Miami) uses nine tracking and intensity models to forecast hurricane movement. • Seven models based on global climate forecasts; two (NHC90/91 and CLIPER) based on statistical analyses of past hurricane trajectories. • Forecasts are for 12h, 24h, 36h, 48h and 72h ahead and are updated at 4h intervals. • Some models are used for ‘early’ stages; others for ‘late’ (i.e. close to landfall). • Average errors vary from ocean to ocean, depending on typical recurvature (Atlantic errors are large)

  16. Mean error (nm) for Atlantic hurricanes (1996-97 seasons) Forecast model

  17. The geography of forecasting error 72 h 48 h 24 h

  18. Estimated annual deaths from hurricanes in the USA

  19. Damages from hurricanes in the USA ($ billions)

  20. Hurricane hazards Storm surge (5-6m common) High winds (see Saffir-Simpson) Intense rainfall X New Orleans (-2m elev.) ~72h to evacuate 1.6M residents. Old and poor (~100 000) who rely on public transport present a major problem. Solution: move them to high floors of skyscrapers? Increasing population at risk (80% of residents of Florida =8M people live within 8 km of coast; 3M within storm surge zone)

  21. El Niño events and tropical storm activity(e.g. 1998 El Niño) • PACIFIC OCEAN - 14 tropical storms in E. Pacific ; 9 developed into hurricanes. • ATLANTIC OCEAN - 14 tropical storms; 10 developed into hurricanes.H. George: most powerful storm in ~200 yrs; hit Puerto Rico, Virgin Is., Domincan Rep., Florida and US Gulf coast - 300 deaths, $5G in damage.H. Mitch: most destructive storm in ~200 yrs; hit Nicaragua - Guatemala - >13 000 dead or missing, $5G in damage.

  22. Global warming and tropical storm activity Emanual (MIT) forecasts:1. that the hurricane season will be extended by 2 months or more in the North Atlantic and Caribbean. 2. that hurricane intensity will increase by more than 50% - attaining maximum wind speeds of >300 km/h (cf. >200 km/h at present).

  23. HURRICANE SEASON 2001 12 - 7 - 3 12 NAMED STORMS 7 HURRICANES 3 MAJOR STORMS

  24. 1995-2000 MOST ACTIVE 6 YEARS ON RECORD 79 NAMED STORMS 49 HURRICANES 24 MAJOR STORMS

  25. PB4Y-2 PRIVATEER(Hurricane Hunter) Lost, Hurricane JANET - 1955

  26. COSMOSPHERE-HURRICANESUN PROVIDES HEAT

  27. ATMOSPHERE-HURRICANE

  28. TEMPERATURE SST 26.5C OR MORE TO A LEAST 46 METERS DEEP

  29. INFLOW-OUTFLOW WARM/MOIST CORIOLIS SHEAR

  30. WINDS 155 MPH = 100 lbs per SQUARE FOOT. SURGE CUBIC YARD SALT WATER = 3/4 TON.

  31. HYDROSPHERE-HURRICANEOCEAN PROVIDES MOISTURE

  32. BIOSPHERE-HURRICANEHABITAT DAMAGE

  33. Board “Growing” in a TreeHurricane Andrew, 1992

  34. ANTHROPOSPHERE/GEOSPHERE-HURRICANE“A-SPHERE”DEATH & DISTRUCTION

  35. FLORIDA KEYS 1935

  36. FLORIDA KEYS 1935

  37. CAMILLE 1969

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