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January 3-4 2008 West Coast Extratropical Cyclone

January 3-4 2008 West Coast Extratropical Cyclone. Henry D. Bartholomew San Francisco State University. The purpose of my study . I want to answer questions like… Why did the low rapidly intensify? Why did it produce strong negative omega?. Outline. Synoptic Overview Strong Winds

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January 3-4 2008 West Coast Extratropical Cyclone

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  1. January 3-4 2008 West Coast Extratropical Cyclone Henry D. Bartholomew San Francisco State University

  2. The purpose of my study • I want to answer questions like… • Why did the low rapidly intensify? • Why did it produce strong negative omega?

  3. Outline • Synoptic Overview • Strong Winds • Heavy Precipitation • Quasigeostrophic Equations Discussion • Quasigeostrophic Diagnosis • Summary and Conclusions

  4. Synoptic Overview • Formed on 3 Jan 2008 • First located south of the Aleutian Islands • Moved east and strengthened • Reached minimum pressure of 956 mb • Impacted California on 4 Jan 2008 • Brought heavy rain and strong winds to CA

  5. Outline • Synoptic Overview • Strong Winds • Heavy Precipitation • Quasigeostrophic Equations Discussion • Quasigeostrophic Diagnosis • Summary and Conclusions

  6. Strong Winds in California • Concord: 45 mph • Chico: 58 mph • SFO: 68 mph • North Oakland: 71 mph • Mt. Diablo: 117 mph Generally, sustained winds of 20-50 mph

  7. Note the increase in wind speeds with a corresponding pressure drop Max Gusts: 65 to 70 mph Minimum Pressure: 997 mb

  8. January 3-4 2008 West Coast Extratropical Cyclone • Synoptic Overview • Strong Winds • Heavy Precipitation • Quasigeostrophic Equations Discussion • Quasigeostrophic Diagnosis • Summary and Conclusions

  9. 24-hour Precipitation Amounts12Z 4 Jan 08 to 12Z 5 Jan 08 • San Francisco: 1.72” • Napa: 1.98” • Oakland: 2.07” • Mt. Diablo: 3.69” • Ben Lomond: 5.74”

  10. January 3-4 2008 West Coast Extratropical Cyclone • Synoptic Overview • Strong Winds • Heavy Precipitation • Quasigeostrophic Equations Discussion • Quasigeostrophic Diagnosis • Summary and Conclusions

  11. Quasigeostrophic Analysis of Storm:QG-Omega Equation and SPDE • QG-Omega Equation • LHS: Omega Term • RHS: Differential vorticity advection, temperature advection, sensible heating, friction terms • SPDE • LHS: 1000 mb relative vorticity tendency • RHS: 500 mb absolute vorticity advection, • 1000 mb horizontal temperature advection terms

  12. QG equations, continued • QG-Omega Equation • SPDE

  13. January 3-4 2008 West Coast Extratropical Cyclone • Synoptic Overview • Strong Winds • Heavy Precipitation • Quasigeostrophic Equations Discussion • Quasigeostrophic Diagnosis • Summary and Conclusions

  14. Quasigestrophic Diagnosis • Will be conducted at three times • 0000 and 1200 UTC 4 Jan • 0000 UTC 5 Jan • Terms in each equation analyzed • Find out general nature of omega, and contributing factors • Find out general nature of development, and contributing factors

  15. 0000 UTC 4 Jan 2008SPDE • Center of low • Positive relative vorticity tendency • Weak absolute vorticity advection • Warm advection • Development of system: • 976 mb. 12 UTC 3 Jan 2008 • 964 mb. 00 UTC 4 Jan 2008

  16. 0000 UTC 4 J an 2008

  17. 0000 UTC 4 Jan 2008 QG-Omega Equation • San Francisco • Negative omega • Strong negative vorticity advection • Weak warm advection • Dominating Term: Temp Advection

  18. 1200 UTC 4 Jan 2008\SPDE • Center of low • Slight negative relative vorticity tendency • Weak absolute vorticity advection • Weak temperature advection • No change in intensity: • Low remains at 964 mb.

  19. 1200 UTC 4 Jan 2008QG-Omega Equation • San Francisco • Negative omega • Weak negative vorticity advection • Strong warm advection • Clear dominating term

  20. 0000 UTC 5 Jan 2008SPDE • Center of low • Slight negative relative vorticity tendency • Weak absolute vorticity advection • Warm advection • Low remains at 964 mb.

  21. 0000 UTC 5 Jan 2008 QG-Omega Equation • San Francisco • Weak omega • Negative along coast, positive inland • Mostly warm advection • Weak vorticity advection

  22. January 3-4 2008 West Coast Extratropical Cyclone • Synoptic Overview • Strong Winds • Heavy Precipitation • Quasigeostrophic Equations Discussion • Quasigeostrophic Diagnosis • Summary and Conclusions

  23. Summary and Conclusions • QG-Omega Equation • SF: Dominating factor: Warm advection • Contributed to strong negative omega

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