1. Data Comparison and Analysis of the Frontal Passage Event on 2 FEB 04
LT C. Sim James, USN
OC 3570 Cruise Project

2. Motivation for this Study
A case day of my Thesis
Model performance along coast lines is variable in reliability due to topography making prediction difficult
It was required for this class…and I love this class…

3. Background
East Pacific High is further south in the winter, therefore it’s all encompassing subsidence is not as important a factor
Air-Sea Temperature difference is not as great (lack of upwelling) and opposite what it is in summer
As a result, Inversions are not as strong
EPH is not blocking so Mid-latitude Cyclones come through and affect the wind/pressure patterns

4. Data Analysis Techniques
MATLAB to ingest and display UDAS files
GARP to display and analyze model fields and Buoy Data
Dick Lind’s old FORTRAN code to extract the sounding data for display

5. Data Sources to be Compared
Shipboard Rawinsonde Data
Shipboard Observational Data
UDAS Data
Buoy Observations
COAMPS Analysis
Shore Station Observation Data
Ft. Ord Wind Profiler Data

6. Synoptic Overview
2 FEB 2004

7. 2 FEB 00Z: Cold front approaches

8. 02 FEB 04 18Z: Cold Front has passed

9. Like waves through the atmosphere, these are the sondes of our lives…
(A sonde by sonde analysis of the frontal passage)

10. Sonde Launch Locations

11. Sonde 21

12. Surface Obs: Sonde 21 Overcast with low lying stratus
Winds from the SE 5-10 kts.

13. Sonde 21 Synoptic 06Z 2 FEB 04

14. Buoy Observations: Sonde 21

15. Sonde 22

16. Sonde 22 Synoptic 14Z 2 FEB 04

17. Surface Obs at Sonde 22 Winds up to twenty two knots and shifted SSW
Low Visibility
Overcast with (cloud type 3)

18. Buoy Observations: Sonde 22

19. Ft. Ord Profiler: 2 FEB 04

20. UDAS for 2 FEB 04

21. Time Series at Ft. Ord

22. Sonde 23

23. Sonde 23 Synoptic 20Z 2FEB 04

24. Surface Obs: Sonde 23
Winds from the South – SW sustained at kts.

25. Buoy Observations: Sonde 23

26. Sonde 25

27. Sonde 25 Synoptic 00Z/03 FEB

28. Buoy Observations: Sonde 25 03FEB 00Z

29. Conclusions (or is this the end as we know it?)
COAMPS winds tended to be 5-10 knots less than observed values on the R/V Pt. Sur
COAMPS can be slow to correct for coastal wind effects
Subjectivity of surface cloud cover observations makes them difficult to rely upon
More than one data source is needed to make a good analysis…not really news, but this drove it home…

30. Questions?