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By Greg Machos December 4, 2003 Agenda Introduction Hurricane Development Essential Ingredients Theories on Tropical Cyclogenesis Category Five Hurricanes--Optimum.

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Presentation on theme: "By Greg Machos December 4, 2003 Agenda Introduction Hurricane Development Essential Ingredients Theories on Tropical Cyclogenesis Category Five Hurricanes--Optimum."— Presentation transcript:


2 By Greg Machos December 4, 2003

3 Agenda Introduction Hurricane Development Essential Ingredients Theories on Tropical Cyclogenesis Category Five Hurricanes--Optimum Intensity Requirements What Happens Inside Category Five Hurricanes Category Five Hurricanes--How They Lose Their Punch Maximum Potential Intensity--Emanuel Analysis of MPI--Persing and Montgomery Causes of Weakening Conclusion

4 Introduction Hurricanes--A Combination of Beauty and Fury Provide A Breathtaking View From Space. Carry A Devastating Punch At The Surface. Classifying Hurricanes--The Saffir-Simpson Scale Categorizes Hurricanes In Terms of Wind And Pressure. Ranges From Category One To Category Five Intensity. Category Five Hurricanes--A Rare Breed Account For Less Than 5% Of All Atlantic Hurricanes. Also Represent Hurricanes At Maximum Efficiency. Cant Sustain Such High Intensity For Long. Due To Changes In Its Environment and Within Itself.

5 Saffir-Simpson Scale* CategorySustained Winds (ms -1 ) Minimum Central Pressure (mb) Storm Surge (meters) Category One Hurricanes33 to 42 ms -1 >=980 mb1.5 meters Category Two Hurricanes43 to 49 ms mb m Category Three Hurricanes50 to 58 ms mb m Category Four Hurricanes59 to 69 ms mb m Category Five Hurricanes>69 ms -1 <920 mb>5.5 meters *Source: Ahrens, Meteorology Today, 2003

6 Long Lasting Category Five Storms* Storm NameYearDuration (hours) Hurricane Dog hours Hurricane David hours Hurricane Mitch hours Hurricane Isabel hours Unamed Hurricane hours Hurricane Camille hours *Source: The Weather Channel, September 2003

7 Hurricane Development Essential Ingredients Sea Surface Temperatures at or above C. Light Winds Aloft. Plenty of moist air from the surface upward. Rotation or spin--Forcing surface winds to converge. Theories--Tropical Cyclogenesis Organized Convection Theory. Heat Engine Theory--Based on Carnot Cycle. Combination of both theories. Analysis--Heat Engine Theory Makes More Sense.

8 Organized Convection Theory* Thunderstorms must be organized. Cold air must be present aloft for instability. Latent heat must be released at upper levels. Latent heat at upper levels results in high pressure. High pressure creates good outflow or exhaust for the storm. *Source, Ahrens, Meteorology Today, 2003

9 Heat Engine Theory* Based on Carnot Cycle. Transfers heat from warm ocean surface (warm reservoir). To the upper levels of the troposphere (cold reservoir). Transfer results from work done by small swirling air currents. Pressure gradient results from temperature difference between the air aloft in the eye, and air aloft at periphery. *Source, Stull, Meteorology for Scientists and Engineers, 2000

10 Category Five Hurricanes--Optimum Meteorological Requirements Sustained Winds Exceeding 69 ms -1. Minimum Central Pressure Below 920 mb or 0.91 atm. Thermodynamic Requirements--Goldilocks Principle Conditions are just right. Sea Surface Temperatures Above 28 0 C. Adequately Moist Air at altitudes between 1.5 to 5 km. Little or no wind shear at upper levels of atmosphere. Rapid Intensification Another characteristic of Category Five Storms. Process takes hurricane from Cat 1 or 2 to Cat 4 or 5. Occurs often in warm eddies, or deep, thick warm water.

11 Inside Category Five Hurricanes Narrow and Well Defined Eye Eye clear because of warm, sinking air in center. Eye narrows to conserve momentum. Classic Buzz Saw Shape Combination of healthy outflow and organized CDO. Outflow acts as exhaust for heat and moisture. Organized Central Dense Overcast--Thunderstorms. Essential for highly efficient heat engine to keep going. Eyewall Replacement Occurs in most major hurricanes. Result of Rapid Intensification. Can cause Concentric Eyewalls.

12 A Look At A Category Five Hurricane* *Source, NOAA, October 26, 1998 Narrow Eye Central Dense Overcast Healthy Outflow

13 References Ahrens, Donald C., 2003: Meteorology today: An introduction to weather, climate, and the environment. Thomson Learning, Inc. Ban, Ray. 1992: Dangers Edge. [Video] The Weather Channel. Bister, M., and K.A. Emanuel, 1998: Dissipative heating and hurricane intensity. Meteorol. Atmos. Phys., 65, Elsner, J.B., and A.B. Kara., 1999: Hurricanes of the North Atlantic: Climate and society. Oxford University Press. Emanuel, Kerry A., 2000: A statistical analysis of tropical cyclone intensity. Mon. Wea. Rev., 128, Emanuel, Kerry A., 1999: Thermodynamic control of hurricane intensity. Nature, 401, Emanuel, Kerry A., 1988: The maximum intensity of hurricanes. J. Atmos. Sci., 45, Hoversten, Paul., 29 September 2000: Scientists study why hurricanes intensify. USA Today. [Online] Iacovelli, Debi., 1999: Concentric eyewalls of hurricanes: An interview with Dr. Hugh E. Willoughby. NOAA Mariners Weather Log, 43, 4-9. Persing, J., and M.T. Montgomery, 2002: Hurricane superintensity. J. Atmos. Sci., 205, Remer, Fred., 2003: Second Law of Thermodynamics. [MS PowerPoint] University of North Dakota. Stull, Roland B., 2000: Meteorology for scientists and engineers: Second edition. Thomson Learning, Inc. Stewart, Stacy. 18 September 2003: Internet interview. Wallace, J.M. and P.V. Hobbs. 1977: Atmospheric science: An introductory survey. Academic Press. Willoughby, Hugh. 13 November 2003: Internet interview.

14 Questions Feel free to use the next few minutes to ask questions.

15 Hope you enjoyed the presentation.

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