January 3-4 2008 West Coast Extratropical Cyclone
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Transcript of January 3-4 2008 West Coast Extratropical Cyclone
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January 3-4 2008 West Coast Extratropical Cyclone
Henry D. BartholomewSan Francisco State University
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The purpose of my study I want to answer questions
like… Why did the low rapidly
intensify? Why did it produce strong
negative omega?
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Outline Synoptic Overview Strong Winds Heavy Precipitation Quasigeostrophic Equations
Discussion Quasigeostrophic Diagnosis Summary and Conclusions
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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
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Outline Synoptic Overview Strong Winds Heavy Precipitation Quasigeostrophic Equations
Discussion Quasigeostrophic Diagnosis Summary and Conclusions
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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
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Note the increase in wind speeds with a corresponding pressure drop
Max Gusts:
65 to 70 mph
MinimumPressure:997 mb
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January 3-4 2008 West Coast Extratropical Cyclone Synoptic Overview Strong Winds Heavy Precipitation Quasigeostrophic Equations
Discussion Quasigeostrophic Diagnosis Summary and Conclusions
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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”
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January 3-4 2008 West Coast Extratropical Cyclone Synoptic Overview Strong Winds Heavy Precipitation Quasigeostrophic Equations
Discussion Quasigeostrophic Diagnosis Summary and Conclusions
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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
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QG equations, continued QG-Omega Equation
SPDE
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January 3-4 2008 West Coast Extratropical Cyclone Synoptic Overview Strong Winds Heavy Precipitation Quasigeostrophic Equations
Discussion Quasigeostrophic Diagnosis Summary and Conclusions
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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
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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
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0000 UTC 4 J an 2008
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0000 UTC 4 Jan 2008QG-Omega Equation San Francisco Negative omega Strong negative vorticity advection Weak warm advection Dominating Term: Temp Advection
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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.
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1200 UTC 4 Jan 2008QG-Omega Equation San Francisco Negative omega Weak negative vorticity advection Strong warm advection Clear dominating term
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0000 UTC 5 Jan 2008SPDE Center of low Slight negative relative vorticity
tendency Weak absolute vorticity advection Warm advection Low remains at 964 mb.
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0000 UTC 5 Jan 2008QG-Omega Equation San Francisco Weak omega Negative along coast, positive
inland Mostly warm advection Weak vorticity advection
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January 3-4 2008 West Coast Extratropical Cyclone Synoptic Overview Strong Winds Heavy Precipitation Quasigeostrophic Equations
Discussion Quasigeostrophic Diagnosis Summary and Conclusions
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Summary and Conclusions QG-Omega Equation SF: Dominating factor: Warm
advection Contributed to strong negative
omega