January 3-5 2008 West Coast Extratropical Cyclone

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January 3-5 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 - PowerPoint PPT Presentation

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  • January 3-5 2008 West Coast Extratropical CycloneHenry D. BartholomewSan Francisco State University

  • The purpose of my studyI want to answer questions likeWhy did the low rapidly intensify?Why did it produce strong negative omega?

  • OutlineSynoptic OverviewStrong WindsHeavy PrecipitationQuasigeostrophic Equations DiscussionQuasigeostrophic DiagnosisSummary and Conclusions

  • Synoptic OverviewFormed on 3 Jan 2008First located south of the Aleutian IslandsMoved east and strengthenedReached minimum pressure of 956 mbImpacted California on 4 Jan 2008Brought heavy rain and strong winds to CA

  • OutlineSynoptic OverviewStrong WindsHeavy PrecipitationQuasigeostrophic Equations DiscussionQuasigeostrophic DiagnosisSummary and Conclusions

  • Strong Winds in California

    Concord: 45 mphChico: 58 mphSFO: 68 mphNorth Oakland: 71 mphMt. Diablo: 117 mphGenerally, sustained winds of 20-50 mph

  • Note the increase in wind speeds with a corresponding pressure dropMax Gusts:65 to 70 mphMinimumPressure:997 mb

  • January 3-5 2008 West Coast Extratropical CycloneSynoptic OverviewStrong WindsHeavy PrecipitationQuasigeostrophic Equations DiscussionQuasigeostrophic DiagnosisSummary and Conclusions

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

  • January 3-5 2008 West Coast Extratropical CycloneSynoptic OverviewStrong WindsHeavy PrecipitationQuasigeostrophic Equations DiscussionQuasigeostrophic DiagnosisSummary and Conclusions

  • Quasigeostrophic Analysis of Storm:QG-Omega Equation and SPDEQG-Omega EquationLHS: Omega TermRHS: Differential vorticity advection, temperature advection, sensible heating, friction terms

    SPDELHS: 1000 mb relative vorticity tendencyRHS: 500 mb absolute vorticity advection,1000 mb horizontal temperature advection terms

  • QG equations, continuedQG-Omega Equation

    SPDE

  • January 3-5 2008 West Coast Extratropical CycloneSynoptic OverviewStrong WindsHeavy PrecipitationQuasigeostrophic Equations DiscussionQuasigeostrophic DiagnosisSummary and Conclusions

  • Quasigestrophic DiagnosisWill be conducted at three times0000 and 1200 UTC 4 Jan0000 UTC 5 Jan Terms in each equation analyzedFind out general nature of omega, and contributing factorsFind out general nature of development, and contributing factors

  • 0000 UTC 4 Jan 2008SPDECenter of low Positive relative vorticity tendencyWeak absolute vorticity advectionWarm advectionDevelopment of system:976 mb. 12 UTC 3 Jan 2008964 mb. 00 UTC 4 Jan 2008

  • 0000 UTC 4 J an 2008

  • 0000 UTC 4 Jan 2008QG-Omega EquationSan FranciscoNegative omegaStrong negative vorticity advectionWeak warm advectionDominating Term: Temp Advection

  • 1200 UTC 4 Jan 2008\SPDECenter of lowSlight negative relative vorticity tendencyWeak absolute vorticity advectionWeak temperature advectionNo change in intensity:Low remains at 964 mb.

  • 1200 UTC 4 Jan 2008QG-Omega EquationSan FranciscoNegative omegaWeak negative vorticity advectionStrong warm advectionClear dominating term

  • 0000 UTC 5 Jan 2008SPDECenter of lowSlight negative relative vorticity tendencyWeak absolute vorticity advectionWarm advectionLow remains at 964 mb.

  • 0000 UTC 5 Jan 2008QG-Omega EquationSan FranciscoWeak omegaNegative along coast, positive inlandMostly warm advection Weak vorticity advection

  • January 3-5 2008 West Coast Extratropical CycloneSynoptic OverviewStrong WindsHeavy PrecipitationQuasigeostrophic Equations DiscussionQuasigeostrophic DiagnosisSummary and Conclusions

  • Summary and ConclusionsQG-Omega EquationSF: Dominating factor: Warm advectionContributed to strong negative omega