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Weather Fronts and Cyclones

Weather Fronts and Cyclones. Weather Systems. Recurring atmospheric circulation patterns Movement of cyclones and anti-cyclones Range in size from km to 1000s of km. Air Masses. North America gets 5 types of air masses Defined by areas of origination

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Weather Fronts and Cyclones

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  1. Weather Fronts and Cyclones

  2. Weather Systems Recurring atmospheric circulation patterns Movement of cyclones and anti-cyclones Range in size from km to 1000s of km
  3. Air Masses North America gets 5 types of air masses Defined by areas of origination Highly variable in terms of temperature and moisture
  4. Weather Fronts
  5. Cold Fronts Cold Front cold air mass advances on a warmer air mass Difference in density causes warm air to rise Blue line with triangles in direction of motion
  6. Cold Front Weather Steep vertical face Result: Heavy rain or snow Long line of thunderstorms Atm pressure tends to increase
  7. Warm Fronts Warm air advances on cooler air Warm air rises on a “ramp” over the cool air Red line with half-circles in direction of motion
  8. Warm Front Weather Slower and less steep than cold front Rising air forms stratus clouds and results in ppt Atm pressure tends to decrease
  9. Stationary Front A non-moving division between air masses Shown as combination of warm and cold fronts
  10. Occluded Front One front overtakes another Cold front typically faster moving Can have warm and cold occluded fronts
  11. Occluded Front Weather Lifting of warm air by fast moving cold air mass creates precipitation
  12. Traveling Cyclones Wave (Extratropical) Cyclones Tropical Cyclones Tornados
  13. Wave Cyclone Wave cyclone over the midwest US Warm winds out of the SW, cold winds out of the NW Notice the difference in precipitation with the warm and cold fronts
  14. Wave Cyclone Air moves counter-clockwise around low pressure System moves from west to east
  15. Wave Cyclone Wave cyclones often originate in the NW and move east Storm evolves as it travels East
  16. Wave Cyclones Wave cyclone over the great lakes Typical “comma” shape
  17. Wave Cyclone Need divergence aloft to draw air up from the earth’s surface and keep the cyclone alive Convergence above the trailing anti-cyclone
  18. Mid-latitude cyclones over North America
  19. Tropical Cyclones What are the conditions necessary to form a tropical storm or hurricane? Unstable Atmosphere Warm Ocean Consistent Winds Coriolis Force (>500 km from equator)
  20. Tropical Cyclones 3 parts: Eye – fundamental property of rotating fluids, strong downdrafts Eye wall – strongest winds, updrafts and downdrafts Rain bands – intense areas of convective ppt
  21. Hurricane Formation
  22. Hurricane Structure
  23. Studying Hurricanes How do forecasters make predictions about the hurricane’s path and intensity?
  24. Air force reserve base in Biloxi, Miss houses WC-130 aircraft that fly into the center of hurricanes
  25. stadium-effect inside the eye of Hurricane Katrina
  26. Dropsonde to measure pressure in the eye – what does this tell you?
  27. Pressure in the eye = 902 millibars (Katrina) 4th lowest pressure ever measured in the Atlantic basin
  28. Intense Convection
  29. Organized system of cloud and thunderstorms with well-defined circulation; wind to 62 km/hr More well-defined circulation; wind to 117 km/hr; storm is named Intense system with “eye” feature wind sustained at > 118 km/hr (75 mph)
  30. Atlantic Names 2002 2003 2004 2005 2006 2007 ArthurBerthaCristobalDollyEdouardFayGustavHannaIsidoreJosephineKyleLiliMarcoNanaOmarPalomaReneSallyTeddyVickyWilfred AnaBillClaudetteDannyErikaFabianGraceHenriIsabelJuanKateLarryMindyNicholasOdettePeterRoseSamTeresaVictorWanda AlexBonnieCharleyDanielleEarlFrancesGastonHermineIvanJeanneKarlLisaMatthewNicoleOttoPaulaRichardSharyTomasVirginieWalter ArleneBretCindyDennisEmilyFranklinGertHarveyIreneJoseKatrinaLeeMariaNateOpheliaPhilippeRitaStanTammyVinceWilma AlbertoBerylChrisDebbyErnestoFlorenceGordonHeleneIsaacJoyceKirkLeslieMichaelNadineOscarPattyRafaelSandyTonyValerieWilliam AndreaBarryChantalDeanErinFelixGabrielleHumbertoIngridJerryKarenLorenzoMelissaNoelOlgaPabloRebekahSebastienTanyaVanWendy Hurricane Names – from World Meteorological Organization
  31. Name Year Name Year Agnes 1972 Eloise 1975 Alicia 1983 Fifi 1974 Floyd 1999 Allen 1980 Flora 1963 Andrew 1992 Fran 1996 Anita 1977 Frederic 1979 Audrey 1957 Georges 1998 Betsy 1965 Gilbert 1988 Beulah 1967 Gloria 1985 Bob 1991 Gracie 1959 Camille 1969 Hattie 1961 Carla 1961 Hazel 1954 Carmen 1974 Hilda 1964 Carol 1965 Hortense 1996 Celia 1970 Hugo 1989 Cesar 1996 Inez 1966 Cleo 1964 Ione 1955 Connie 1955 Janet 1955 David 1979 Joan 1988 Keith 2000 Diana 1990 Klaus 1990 Lenny 1999 Diane 1955 Luis 1995 Donna 1960 Marilyn 1995 Dora 1964 Mitch 1998 Edna 1968 Opal 1995 Elena 1985 Roxanne 1995 Retired Hurricane Names
  32. Tropical Storms Given what we know about the formation of tropical storms: Where would they originate? When would they occur?
  33. Tropical Storm Life Span
  34. Tropical Storm Life Span
  35. Tropical Storm Life Span How do tropical storms and hurricanes dissipate? Cooler ocean waters Landfall (no warm water source) Land is rough surface, drag weakens convection
  36. Hurricanes and Climate Change How can we expect the number and intensity of hurricanes to change if climate is warming?
  37. Sea Surface Temperatures Webster et al, 2005
  38. Number of Hurricanes and Tropical Storms
  39. Hurricanes in Different Regions of the World
  40. Hurricane Intensity
  41. Hurricane Power Power Dissipation Index (PDI): maximum wind x life span = energy expended
  42. Hurricane Damage Why is hurricane damage increasing with time? Hurricane Andrew (1992) was most expensive natural disaster in history - $25 million
  43. Effects of Katrina
  44. Flooding and Oil Spills
  45. Tornados
  46. Tornado Formation Form in severe thunderstorms called supercells Boundary of cold, polar air and warm moist tropical air Need highly unstable atmosphere which causes rapid uplift
  47. Tornado Formation
  48. Supercell Formation – Twisting Thunderstorm
  49. Which way do tornados rotate?
  50. Large Hail Formation
  51. Tornado Facts Short lived (similar to thunderstorms) 75% occur in United States 1000 per year on earth
  52. Tornado Occurrence
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