Isentropic Analysis

Next Steps: Lab Activity

This lab activity allows you to explore the thermal and dynamic structure of a midlatitude cyclone using the isentropic concepts presented here, as well as in the more standard pressure level sense. You can examine plan-view loops of several variables in the first set of tabs below, and cross-sections are available in a second set of tabs, along with a map showing their locations. Five times are presented - the loops begin at 12Z on Mar. 2, 2012 and subsequent images are shown at 6-hr intervals. All data are NAM analyses from NOAA. A set of questions precedes the imagery - consult your instructor to determine which questions and/or maps are assigned.

Questions

  1. Examine the loop of MSLP and 1000 mb temperatures in the first set of tabs to familiarize yourself with the case. Describe the cyclone that develops in terms of its initial location and strength (in mb), the direction of its track and final location in frame 5, and characterize any associated fronts in terms of frontal type and their locations relative to the center of low pressure
  2. Examine the loop of 850 mb potential temperature (theta) and winds in the second tab. Describe the evolution of cold air and warm air advection regimes in terms of areal size, position within the cyclone, and relative strength over time. Outline the total area of warm air advection in red, and cold air advection in blue, on the 3rd frame map here. Hatch or shade in the area of strongest warm air and cold air advections. This map has a white background for those wishing to print and peform hand analysis instead of using an electronic graphics program: 850mb Theta and Winds, Frame 3
  3. Examine the loop of 500 mb absolute vorticity and heights in the third tab. Describe the evolution of the vorticity maximum associated with the cyclone in terms of areal size, position within the cyclonesystem, and relative strength over time. Outline the area of positive vorticity advection in red on the 3rd frame map here. This map has a white background for those wishing to print and peform hand analysis instead of using an electronic graphics program: 500mb Vorticity and Heights, Frame 3
  4. Examine the loop of 300 mb isotachs and heights in the fourth tab. Describe the evolution of the jet streak associated with the cyclone in terms of areal size and relative strength over time. Describe any theoretical convergence/divegence and transverse circulations that are relevant with respect to the strength and location of the cyclone center. Analyze the jet streak axis and its quadrants, labeling areas of upper level convergence with a red "C" and divergence with a blue "D" on the 3rd frame map here. This map has a white background for those wishing to print and peform hand analysis instead of using an electronic graphics program: 300mb Isotachs and Heights, Frame 3
  5. Now examine the loop of pressure and system-relative winds on the 296K surface. Describe the evolution of ascent and descent on the 296K surface in terms of areal size, position within the cyclone system, and relative strength over time. Analyze vertical motion by outlining the area of ascent in red and descent in blue on the 3rd frame map here. Hatch or shade in the strongest ascent and descent. This map has a white background for those wishing to print and perform hand analysis instead of using an electronic graphics program: 296K Pressure and System Relative Winds, Frame 3
  6. How does the size of the areas of ascent and descent on the 296K surface compare to that of the 850mb warm air and cold air advection areas? The 500 mb positive vorticity advection areas? The 300 mb divergent areas?
  7. How does the position of the areas of ascent and descent on the 296K surface (relative to the cyclone center) compare to that of the 850mb warm air and cold air advection areas? The 500 mb positive vorticity advection areas? The 300 mb divergent areas?
  8. Examine the cross sections in the second set of tabs. Two of the cross sections cut through the warm front, while two cut through the cold front. Compare and contrast the slope of and static stability surrounding the: 1) warm front and, 2) cold front as revealed by the potential temperature contours in the cross sections. Cite specific cross-sections, contour values and animation frames as needed to support your answers.
  9. Characterize any differences in frontal structure revealed by the northern and southern cross sections through the cold front; do the same for the eastern and western cross sections through the warm front
  10. Where do the fronts typically reside with respect to the jet core? Is there any difference in this regard between the warm and cold front? Briefly explain.