10.4. Step 2: Meteorological Consistency#

Make your analysis meteorologically consistent.

Your analysis should be consistent in both time and space. Remember that the atmosphere is a fluid in which events evolving upstream/downstream, above/below and at previous times all influence the current weather situation and this fact needs to be reflected in your analyses. Examine maps from different pressure levels to make sure everything is consistent (e.g., a typical cyclone will tilt to the west with height). If you have a time series of maps, do features evolve relatively smoothly or does the pattern take an unexplained ‘jump’? If you have maps from several times at the same level and/or several levels at the same time, you can use these charts to help with a particular analysis.

Except for the near surface, meteorological fields are continuous and usually continuously differentiable. This means that your analysis should be (for the most part) smooth, particularly as you move up through the atmosphere. Height and pressure contours should curve to represent the large-scale pattern, without a lot of wiggles present. Spacing and direction of these contours should be consistent with the wind information. If the height field aloft suggests the presence of a short wave, check to see if the wind field agrees.

Meteorological Relationships#

  • Geostrophic wind balance

    • requires wind speeds to be greatest in regions of tightest gradient

  • Gradient wind balance

    • requires a stronger wind for a given contour spacing around an anticyclone (supergeostrophic) than around a cyclone (subgeostrophic)

  • Troughs tend to tilt toward cold air

  • Ridges tend to tilt toward warm air

  • Jet streaks over low-level temperature gradients

Keep in mind where the gradient/geostrophic assumption is good and where it is bad and where the ageostrophic wind is important. Examples include frictionally induced cross-contour flow at the surface, an isallobaric wind component where there are rapid changes in the pressure or height fields, and transverse circulations around jet streaks aloft.