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Overview of Hurricanes

Overview of Hurricanes. Carl Schreck. Ingredients. Lifecycle. Climatology. Data. Tropical Cyclone Lifecycle. Ingredients. Lifecycle. Climatology. Data. Tropical Depression. Winds < 35 kts Numbered, but not named Semi-organized group of thunderstorms. Ingredients. Lifecycle.

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Overview of Hurricanes

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  1. Overview of Hurricanes Carl Schreck Ingredients Lifecycle Climatology Data

  2. Tropical Cyclone Lifecycle Ingredients Lifecycle Climatology Data

  3. Tropical Depression • Winds < 35 kts • Numbered, but not named • Semi-organized group of thunderstorms Ingredients Lifecycle Climatology Data

  4. Tropical Storm • Winds 35–63 kts • ≈ 11 per year in the Atlantic • Named • More circular/spiral, but no eye Ingredients Lifecycle Climatology Data

  5. Hurricane • Winds ≥ 64 kts • ≈ 6per year in the Atlantic • Eye develops • Different names around the world: • Hurricane in the Atlantic and East Pacific • Typhoon in West Pacific • Cyclone in Indian Ocean and South Pacific • “Tropical Cyclone” is the generic/scientific term Ingredients Lifecycle Climatology Data

  6. Major Hurricane • Winds ≥ 96 kts • ≈ 2-3 per year in the Atlantic • Category 3–5 on the Saffir–Simpson Scale • Strong and dangerous storms • Well-defined, circular eye Ingredients Lifecycle Climatology Data

  7. Hurricane Ingredients: Thermodynamic • Deep warm ocean layer • Warm oceans are the energy source for hurricanes • But hurricanes can mix cold water upward if the warm water is too shallow • Conditionally unstable atmosphere • Warm air rises, but only if it’s warmer than its surroundings • Moist mid-troposphere • Dry air 2-3 km from the surface can cause cold downdrafts ww2010.atmos.uiuc.edu Ingredients Lifecycle Climatology Data

  8. Hurricane Ingredients: Dynamic • Pre-existing convection • Needs organized thunderstorms to get things going • Cyclonic low-level vorticity • Counter-clockwise spinning winds help organize the thunderstorms • Associated with low pressure • Weak vertical wind shear • Tilting winds can knock the storm over Ingredients Lifecycle Climatology Data

  9. Vertical Wind Shear • Wind shear is defined as the wind vector difference between the 850 and 200 mb level (arbitrary) Good – latent heat can concentrate in one area Bad – convection torn apart High westerly shear Low easterly shear In general, low values (< 20 kt) of vertical wind shear are desired. Ingredients Lifecycle Climatology Data Courtesy of C.C. Hennon, UNC Asheville

  10. Tropical Waves Berry et al. (2007, Mon. Wea. Rev.) • Thunderstorm systems with wave-like properties • Move westward with a period of 3–6 days • Common over West Africa • Provides storms with cyclonic vorticity and convection Ingredients Lifecycle Climatology Data

  11. Main Development Region • Warm Ocean Temperatures • Supply of Tropical Waves from Africa • 10°N to 20°N • 20°W to 60°W or 80°W Ingredients Lifecycle Climatology Data

  12. Saharan Air Layer • Dry air from Sahara can weaken storms • Dust blocks the sun and cools the ocean Zipser et al. (2009, BAMS) climate.nasa.gov Ingredients Lifecycle Climatology Data

  13. Global Tropical Cyclones Knapp et al. (2010, BAMS) Ingredients Lifecycle Climatology Data

  14. Storms Per Year • Bars depict number of named systems (open/yellow), hurricanes (hatched/green), and category 3 or greater (solid/red), 1886-2004 nhc.noaa.gov/climo Ingredients Lifecycle Climatology Data

  15. Atlantic Hurricane Climatology Ingredients Lifecycle Climatology Data

  16. June Ingredients Lifecycle Climatology Data

  17. July Ingredients Lifecycle Climatology Data

  18. August Ingredients Lifecycle Climatology Data

  19. September Ingredients Lifecycle Climatology Data

  20. October Ingredients Lifecycle Climatology Data

  21. November Ingredients Lifecycle Climatology Data

  22. Best Track Data • Historical record of tropical cyclone locations and intensities • Constructed after each season by the warning agencies • Best estimate using all available data nhc.noaa.gov Ingredients Lifecycle Climatology Data

  23. Tropical Cyclone Observations • Weather stations • Buoys • Ships • Radar • Aircraft Reconnaissance • Visible/Infrared Satellites • Microwave satellites • Satellite estimates account for vast majority of the record Courtesy of Jack Beven (NOAA/NHC) Ingredients Lifecycle Climatology Data

  24. Tropical Cyclone Observations • Weather stations • Buoys • Ships • Radar • Aircraft Reconnaissance • Visible/Infrared Satellites • Microwave satellites • Satellite estimates account for vast majority of the record Courtesy of Jack Beven (NOAA/NHC) Ingredients Lifecycle Climatology Data

  25. Which image on the right is the closest match for this image of Hurricane Katrina?

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