2. Shapiro, M. A., 1984: Meteorological tower measurements of a surface cold front. Mon. Wea. Rev., 112, 1634-1639. Shapiro (1984)

3. BAO tower WNW downslope flow Temperatures (°C) winds (barb = 10 kts) The passage of a strong cold front in eastern Colorado We will be interested in the structure of this front as it passes the Boulder Atmospheric Observatory tower

4. The Boulder Atmospheric Observatory Tower located in Erie, Colorado near I-25

5. Cross section of the cold front that passed the BAO tower on 24 March 1982 Based on a rawinsonde at Denver, a radiometer temperature profile, a lidar wind profile and surface data

6. Potential temperature (K, solid) and front normal wind component (m/s, dashed) Two minutes!!! 300 meters superadiabatic lapse rate

7. Vertical motion (m/s) measured by sonic anemometers on the tower Frontal boundaries denoted by solid lines

8. Miller 2-D frontogenesis function (neglecting diabatic processes and turbulence) Change in potential temperature gradient following parcel Confluence acting on  gradient Shear acting on  gradient Tilting of vertical  gradient Can’t evaluate this - so assume negligible based on surface data Do the flow fields suggest that frontal contraction was occurring at the time the front passed the tower?

9. Miller 2-D frontogenesis function (neglecting diabatic processes and turbulence) Change in potential temperature gradient following parcel Confluence acting on  gradient Shear acting on  gradient Tilting of vertical  gradient confluence term

10. Miller 2-D frontogenesis function (neglecting diabatic processes and turbulence) Change in potential temperature gradient following parcel Confluence acting on  gradient Shear acting on  gradient Tilting of vertical  gradient Tilting term

11. Miller 2-D frontogenesis function (neglecting diabatic processes and turbulence) Change in potential temperature gradient following parcel Confluence acting on  gradient Shear acting on  gradient Tilting of vertical  gradient Total frontogenesis Frontolytical Frontogenetical