1. January 3-5 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?

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

5. 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

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

7. 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 mph

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

9. January 3-5 2008 West Coast Extratropical Cyclone
Synoptic Overview
Strong Winds
Heavy Precipitation
Quasigeostrophic Equations Discussion
Quasigeostrophic Diagnosis
Summary and Conclusions

10. 24-hour Precipitation Amounts 12Z 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”

11. January 3-5 2008 West Coast Extratropical Cyclone
Synoptic Overview
Strong Winds
Heavy Precipitation
Quasigeostrophic Equations Discussion
Quasigeostrophic Diagnosis
Summary and Conclusions

12. Quasigeostrophic Analysis of Storm: QG-Omega Equation and SPDE
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

13. QG equations, continued
QG-Omega Equation
SPDE

14. January 3-5 2008 West Coast Extratropical Cyclone
Synoptic Overview
Strong Winds
Heavy Precipitation
Quasigeostrophic Equations Discussion
Quasigeostrophic Diagnosis
Summary and Conclusions

15. 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

16. 0000 UTC 4 Jan 2008 SPDE 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

19. 0000 UTC 4 J an 2008

21. 0000 UTC 4 Jan 2008 QG-Omega Equation
San Francisco
Negative omega
Strong negative vorticity advection
Weak warm advection
Dominating Term: Temp Advection

22. 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.

23. 1200 UTC 4 Jan 2008 QG-Omega Equation
San Francisco
Negative omega
Weak negative vorticity advection
Strong warm advection
Clear dominating term

24. 0000 UTC 5 Jan 2008 SPDE Center of low
Slight negative relative vorticity tendency
Weak absolute vorticity advection
Warm advection
Low remains at 964 mb.

25. 0000 UTC 5 Jan 2008 QG-Omega Equation
San Francisco
Weak omega
Negative along coast, positive inland
Mostly warm advection
Weak vorticity advection

26. January 3-5 2008 West Coast Extratropical Cyclone
Synoptic Overview
Strong Winds
Heavy Precipitation
Quasigeostrophic Equations Discussion
Quasigeostrophic Diagnosis
Summary and Conclusions

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