Ageostrophic Wind and Thermal Wind. Assignment 8. Due April 4

Review the information on the ageostrophic and thermal wind in the Djuric text.

Model forecast guidance from the Eta model initialized at 00z 20 March will be used, the beginning point of your manual analyses.

Use Garp to access the model forecast sequence.

1. Using your manual analyses, briefly evaluate the skill of the 12 h and 24 h forecasts of height and temperature at 700, 500, and 300 mb. How well did the model forecast the movement of the closed low over the eastern U.S.? The developing low over the western U.S.? Other features of interest?

2. Overlay geopotential height and wind at 500 mb. Identify locations and times where/when the flow crosses height contours.

3. Now add the geostrophic wind at 500 mb. Identify locations/times where/when the flow is nearly geostrophic and where it is not. Are there locations where the flow is ageostrophic but parallel to the height contours? Why?

4. Clear the screen. Start with the height at 500 mb again and add the ageostrophic wind. Where/when is the actual wind clearly subgeostrophic? Supergeostrophic?

5. Clear the screen, plot 500 mb temperature. Overlay the thickness of the 300-700 mb layer. How do the two fields compare?

6. Clear the screen, plot 300 mb height, 700 mb height, and the thickness of the 300-700 mb layer. Where do the thickness contours intersect the 300 and 700 mb contours?

7. Clear the screen. Overlay the thickness of the 300-700 mb layer and the thermal wind of the 300-700 mb layer. What is the relationship of the thickness to the thermal wind? Relative to the direction from which the thermal wind is "blowing" what direction is the cold and warm air?