1. Samuel Roback, Emily Padvorac, Danielle Dillane, Sinead Lockhart
Group 6 - Rossby Waves
Samuel Roback, Emily Padvorac, Danielle Dillane, Sinead Lockhart

2. (#2) at 12z
Here the cyclone is located in the western Pacific Ocean. Northwest of the cyclone there is a trough (denoted by the negative eddy height values and downward bulge of the 10-4 abs vort contour due to the positive vort in the trough). A ridge is located to the east of this trough. Neither is very amplified and flow downstream of the ridge is close to zonal.

3. (#2) at 12z
24 hours later the cyclone has moved northward and appears to be interacting with the trough that was previously to its northwest. This trough has amplified. The ridge downstream of this trough has now propagated eastward and is located over the N-Central Pacific Ocean. This ridge has changed little in its magnitude.

4. (#2) at 12z
24 hours later the cyclone has moved north and is located in the northwest Pacific between the trough and the ridge. The cyclone now also appears to be amplifying the western periphery of the ridge located over the N-Central Pacific Ocean. This is seen by the positive eddy heights to the east of the cyclone and a bulge northward in the 10-4 abs vort contour (neg vort w/ ridge)

5. (#3) Estimated Rossby Wave Phase Speed
Sources of Error in Calculation
The longitude was an approximation by looking at the map.
The ridge spanned a distance of latitude, so the average latitude of the ridge was used in the longitude distance calculation.
16.7m/s or 18.4 deg/day

6. (#4) Estimated Rossby Wave Phase Speed from Hovmӧller Diagram
This value is not consistent with the value we calculated previously. This could easily be due to the approximations that were made in these calculations.
Date
Longitude
12Z
200੦
00Z
150੦
= .5੦/h or 12੦/day
(18.4੦/day from previous approximation)

7. (#5) Hovmӧller Diagram Group Velocity
The group velocity we calculated was higher than the phase speed we calculated for the ridge.

8. #6
The lower tropospheric ridges appear to be weaker in magnitude than those of the upper troposphere. Additionally the troughs in the lower troposphere appear to be stronger than those at the upper troposphere. All of the lower tropospheric features are located downstream of the upper level troughs/ridges.

9. (#7) 12Z September 25
The cyclone moves northward perpetrating the flow which creates the Rossby Wave. This can be seen by the building of the ridge to the east of the cyclone.

10. (#7) 12Z September 26
The Rossby Wave propagates downstream and deepens the trough located over the N-Eastern Pacific Ocean.

11. (#7) 12Z September 27
As the wave continues to move eastward the ridge over the western US is amplified.

12. (#7) 12Z September 28
3 days later the wave continues to propagate eastward. This can be seen by the deepening of the trough along the US east coast.

13. (#7) 12Z September 29
The Rossby wave is significantly dampened and is no longer noticeable by day 4. Flow downstream of the weakening E-US trough only resembles weak ridging.

14. #7 (compare)
Our trough/ridge pattern generally followed the trough/ridge pattern on the Hovmoller diagram. The times when when trough/ridges were the strongest coincided with the similar longitudes and times on the Hovmoller diagram when the height anomalies were strongest.