2. ATM OCN 100 Summer 2002 1 ATM OCN 100 - Summer 2002 LECTURE 25 (con’t.) MID-LATITUDE WEATHER SYSTEMS: PART II: THE EXTRATROPICAL CYCLONE A. Introduction B. The Norwegian Model of Extratropical Cyclones C. Observed Weather Features surrounding Extratropical Cyclones D. Life Cycle of an Extratropical Cyclone

3. ATM OCN 100 Summer 2002 2Announcements u Homework 7: –Has been posted at –http://www.aos.wisc.edu/~hopkins/aos100/homework http://www.aos.wisc.edu/~hopkins/aos100/homework –Will be due this afternoon NLT 4 PM (my mailbox) u Homeworks 1-6: –Have been graded and are available up front; please retrieve yours –Answer Keys are posted on the Web at: –http://www.aos.wisc.edu/~hopkins/aos100/homework; http://www.aos.wisc.edu/~hopkins/aos100/homework u Final Exam: –Will be held @ 2:45 PM on Fri. 21 Dec 2001 in Rm. 1100 Grainger Hall –The exam help sheet has been posted at: –http://www.aos.wisc.edu/~hopkins/aos100/exams. http://www.aos.wisc.edu/~hopkins/aos100/exams

4. MADISON’S CURRENT WEATHER Madison Weather at 1000 AM CDT 7 AUG 2002 Updated twice an hour at :05 and :25 Sky/Weather: MOSUNNY Temperature: 68 F (20 C) Dew Point: 57 F (13 C) Relative Humidity: 68% Wind: E3 MPH Barometer: 30.33S (1027.1 mb)

5. ATM OCN 100 Summer 2002 4 Last 24 hrs in Madison FOG

6. ATM OCN 100 Summer 2002 5http://www.ssec.wisc.edu/data/comp/cmoll.mpg

7. 6 CURRENT VISIBLE TS CRISTOBAL

8. ATM OCN 100 Summer 2002 7 CURRENT IR TS CRISTOBAL

9. ATM OCN 100 Summer 2002 8 Current Surface Weather Map with Isobars (“iso” = equal & “bar” = weight), Fronts and Radar

10. ATM OCN 100 Summer 2002 9 Current Surface Winds with Streamlines & Isotachs (“iso” = equal & “tach” = speed) L L H L L L H L H H LL H H L H H L H L H H L L

11. ATM OCN 100 Summer 2002 10 Current Temperatures ( ° F) & Isotherms (“iso” = equal +”therm” = temperature)

12. ATM OCN 100 Summer 2002 11 Current Temperatures ( o F) – 24 Hrs Ago

13. ATM OCN 100 Summer 2002 12 Current Dewpoints ( o F)

14. ATM OCN 100 Summer 2002 13 Current 34,000 ft. Winds & Jet Stream with Streamlines & Isotachs (“iso” = equal & “tach” = speed) Trough Trough Ridge

15. ATM OCN 100 Summer 2002 14 Tomorrow AM Forecast Map

16. ATM OCN 100 Summer 2002 15 Announcements u Homework #5 is Today (NLT 3:30 PM either in my mailbox or at my office) http://www.aos.wisc.edu/~hopkins/aos100/homework http://www.aos.wisc.edu/~hopkins/aos100/homework u 3 rd Hour Exam is scheduled for Tomorrow. See Review Sheet that has been posted at: http://www.aos.wisc.edu/~hopkins/aos100/exams http://www.aos.wisc.edu/~hopkins/aos100/exams u If you have ??, please see me.

17. ATM OCN 100 Summer 2002 16 Cold Front see Fig. 11.5 of Moran & Morgan (1997)

18. ATM OCN 100 Summer 2002 17 Cold Front (con’t.) see Fig. 11.5 of Moran & Morgan (1997)

19. ATM OCN 100 Summer 2002 18 Warm Front see Fig. 11.3 of Moran & Morgan (1997)

20. ATM OCN 100 Summer 2002 19 Warm Front (con’t.) see Fig. 11.3 of Moran & Morgan (1997)

21. ATM OCN 100 Summer 2002 20 Stationary Front see Fig. 11.2 of Moran & Morgan (1997)

22. ATM OCN 100 Summer 2002 21 Occluded Fronts see Figs. 11.7 & 11.8 of Moran & Morgan (1997)

23. ATM OCN 100 Summer 2002 22 ATM OCN 100 – Summer 2002 LECTURE 28 MID-LATITUDE WEATHER SYSTEMS: PART II: THE EXTRATROPICAL CYCLONE A. INTRODUCTION – Practical Problems F What is nature of mid-latitude storm systems? F How to predict midlatitude storm systems – Historical Perspective

24. ATM OCN 100 Summer 2002 23 Current Upper Air

25. ATM OCN 100 Summer 2002 24 Tomorrow’s 6 AM Forecast

26. ATM OCN 100 Summer 2002 25 B. THE NORWEGIAN or POLAR FRONT (WAVE CYCLONE) MODEL u Designation of Extratropical Cyclones u Distinguishing Features of a Mature Polar Front Cyclone

27. ATM OCN 100 Summer 2002 26 Distinguishing Features: Typical cyclone tracks Extratropical cyclones Tropical cyclones

28. ATM OCN 100 Summer 2002 27 B. THE NORWEGIAN or POLAR FRONT (WAVE CYCLONE) MODEL u Designation of Extratropical Cyclones u Distinguishing Features of a Mature Polar Front Cyclone: – Fronts; – Cold Air Vs. Warm Sector; – Comma-Shaped Cloud Patterns...

29. ATM OCN 100 Summer 2002 28 Distinguishing features of the POLAR FRONT CYCLONE MODEL FRONTS Cold air vs. Warm Sector

30. ATM OCN 100 Summer 2002 29 A comma shaped cloud pattern

31. ATM OCN 100 Summer 2002 30 Occluded Cyclone over British Isles

32. ATM OCN 100 Summer 2002 31 A Tropical cyclone with circular cloud bands & eye (Hurricane Mitch, 26 Oct 1998)

33. ATM OCN 100 Summer 2002 32 C. OBSERVED WEATHER FEATURES Surrounding the Model Cyclone u Fronts - (The signature) u Temperature Fields u Pressure Fields & Pressure Tendency Fields u Wind Fields u Cloud Fields u Precipitation & Other Significant “Weather” Events

34. ATM OCN 100 Summer 2002 33 C. OBSERVED WEATHER FEATURES see Fig. 11.13 of Moran & Morgan (1997)

35. ATM OCN 100 Summer 2002 34 Wind Field around a cyclone - Observed Surface Winds

36. ATM OCN 100 Summer 2002 35 Wind Field around a cyclone

37. ATM OCN 100 Summer 2002 36 Wind Field around a cyclone - Observed Surface Winds

38. ATM OCN 100 Summer 2002 37 Composite cyclone weather

39. ATM OCN 100 Summer 2002 38 Composite cyclone weather

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51. 50 Principal Storm Tracks see Fig. 11.16 of Moran & Morgan (1997)

52. ATM OCN 100 Summer 2002 51 Lee-slope Cyclogenesis See Fig.1 pg. 275, Moran & Morgan (1997)

53. ATM OCN 100 Summer 2002 52 E. MOVEMENTS OF EXTRATROPICAL WAVE CYCLONES (con’t.) u Principal Cyclone Tracks over North America u Time Sequences of Weather Events - Single Point Forecasting

54. ATM OCN 100 Summer 2002 53 Weather along Storm Tracks (A) Warm Side vs. (B) Cold side see Fig. 11.15 of Moran & Morgan (1997)

55. ATM OCN 100 Summer 2002 54 Weather on Warm Side Windy, warm & rainy in Madison

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61. 60 Weather Conditions around Extratropical Cyclone

62. ATM OCN 100 Summer 2002 61 Warm or South Side of Cyclone

63. ATM OCN 100 Summer 2002 62 Weather on Cold Side Development of a 5 inch snow storm in Madison (with temperatures in the teens)

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68. 67 Weather Conditions around Extratropical Cyclone

69. ATM OCN 100 Summer 2002 68 Weather Conditions around Extratropical Cyclone

70. ATM OCN 100 Summer 2002 69 D. LIFE CYCLE OF AN EXTRATROPICAL WAVE CYCLONE “THE OCCLUSION PROCESS” u Storm Formation ( or cyclogenesis) u Early Developing Stage u Mature Stage u Occluding Stage u Occluded Stage

71. ATM OCN 100 Summer 2002 70 Life Cycle of an Extratropical Cyclone See Fig. 11.9 Moran & Morgan (1997)

72. ATM OCN 100 Summer 2002 71 Incipient Cyclone Stage in the Life Cycle of an Extratropical Cyclone See Fig. 11.9A Moran & Morgan (1997)

73. ATM OCN 100 Summer 2002 72 The Surface Low & the Jet

74. ATM OCN 100 Summer 2002 73 Linkage between surface weather systems & winds aloft See Fig. 10.22 Moran & Morgan (1997)

75. ATM OCN 100 Summer 2002 74 Wave Cyclone Stage in the Life Cycle of an Extratropical Cyclone See Fig. 11.9B Moran & Morgan (1997)

76. ATM OCN 100 Summer 2002 75 Occluding Stage in the Life Cycle of an Extratropical Cyclone See Fig. 11.9C Moran & Morgan (1997)

77. ATM OCN 100 Summer 2002 76 Bent-Back Occlusion Stage in the Life Cycle of an Extratropical Cyclone See Fig. 11.9D Moran & Morgan (1997)

78. ATM OCN 100 Summer 2002 77 DISTINGUISHING CHARACTERISTICS of A MATURE EXTRATROPICAL CYCLONE

79. ATM OCN 100 Summer 2002 78 E. OTHER FEATURES OF THE POLAR FRONT CYCLONE MODEL u Cyclone Families u Regions of Cyclogenesis – Lee-side of mountains – Along east coasts of continents u Energetics of Cyclogenesis - The Driving Force u Limitations & Complications of Polar Front Model

80. ATM OCN 100 Summer 2002 79 Cyclones along the Polar Front

81. ATM OCN 100 Summer 2002 80 Cyclone Families from TIROS

82. ATM OCN 100 Summer 2002 81 Occluded Cyclone over British Isles

83. ATM OCN 100 Summer 2002 82 F. MOVEMENTS OF EXTRATROPICAL WAVE CYCLONES u General Movements u Regions of Cyclogenesis – Lee-side of mountains – Along east coasts of continents u Principal Cyclone Tracks over North America

84. ATM OCN 100 Summer 2002 83 E. MOVEMENTS OF EXTRATROPICAL WAVE CYCLONES u General Movements –Steering winds aloft

85. ATM OCN 100 Summer 2002 84 Zonal Circulation Regime Figure 10.10 Moran & Morgan (1997)

86. ATM OCN 100 Summer 2002 85 Meridional Circulation Regime Figure 10.10 Moran & Morgan (1997)

87. ATM OCN 100 Summer 2002 86 Stagnant Circulation Regime with Cut-off Lows & Blocking Highs Figure 10.13 Moran & Morgan (1997)

88. ATM OCN 100 Summer 2002 87 E. MOVEMENTS OF EXTRATROPICAL WAVE CYCLONES (con’t.) u General Movements u Regions of Cyclogenesis – Lee-side of mountains – Along east coasts of continents

89. ATM OCN 100 Summer 2002 88 Lee-slope Cyclogenesis See Fig.1 pg. 275, Moran & Morgan (1997)

90. ATM OCN 100 Summer 2002 89 E. MOVEMENTS OF EXTRATROPICAL WAVE CYCLONES (con’t.) u General Movements u Regions of Cyclogenesis – Lee-side of mountains – Along east coasts of continents u Principal Cyclone Tracks over North America

91. ATM OCN 100 Summer 2002 90 F. MOVEMENTS OF EXTRATROPICAL WAVE CYCLONES u General Movements u Principal Cyclone Tracks over North America

92. ATM OCN 100 Summer 2002 91 Storm Tracks see Fig. 11.16 of Moran & Morgan (1997)

93. ATM OCN 100 Summer 2002 92 E. MOVEMENTS OF EXTRATROPICAL WAVE CYCLONES (con’t.) u General Movements u Regions of Cyclogenesis u Principal Cyclone Tracks over North America u Time Sequences of Weather Events - Single Point Forecasting

94. ATM OCN 100 Summer 2002 93 E. MOVEMENTS OF EXTRATROPICAL WAVE CYCLONES (con’t.) u Principal Cyclone Tracks over North America u Time Sequences of Weather Events - Single Point Forecasting

95. ATM OCN 100 Summer 2002 94 Weather along Storm Tracks (A) Warm Side vs. (B) Cold side see Fig. 11.15 of Moran & Morgan (1997)

96. ATM OCN 100 Summer 2002 95 G. WINTER STORMS u Definitions u Winter Weather Conditions – Hazards of Winter Storms F HEAVY SNOW F ICE STORMS F STRONG WINDS – Ingredients of a Winter Storm F COLD AIR F MOISTURE F LIFT

97. ATM OCN 100 Summer 2002 96 See Figure 11.14 Moran & Morgan (1997)

98. ATM OCN 100 Summer 2002 97 WINTER STORMS (con’t.) u Blizzards – Winter weather condition lasting 3 hours or more with: F Strong winds (35 mph or more); F Snow & blowing snow with visibility less than 1/4 mile.

99. ATM OCN 100 Summer 2002 98 WINTER STORMS (con’t.) u Public Information Dissemination & Public Safety Precautions – Blizzard warnings; – Winter storm watches & warnings; – Ice storm warnings; – High wind warnings; – Wind chill warnings.

100. ATM OCN 100 Summer 2002 99 Cross Section thru a cyclone

101. ATM OCN 100 Summer 2002 100 An extratropical cyclone