Reading 5a: Some Rules of Contouring

 

§      All contours eventually connect because they form closed curves, but can end at map borders (they connect off of the map space).

 

§      Contours should be smooth curves, except at fronts, outflow boundaries, surrface troughs, drylines, where contours should be kinked AWAY from low pressure.

 

§      Contours should be labeled at convenient locations and at ends near the periphery of charts.

 

§      Contours should be drawn at conventional intervals and at conventional initial values (i.e., on surface chart, 4 mb intervals (2 mb subsynoptic) starting at 1000 mb etc.).

 

§      Areas of low and high pressures (heights) should be labeled with red "L" (or "Low") and blue "H" (or "High"), respectively.

 

§      Winds should be in either geostrophic/gradient balance or "friction" (boundary layer) wind balance with contours depending upon analysis level. Disturbances with wavelength less than about 200 km or so should NOT appear on contour patterns for 700 mb and above. This is because the radiosonde network is too coarse to resolve disturbances of this scale. Such disturbances appearing on computer analyzed charts are usually spurious and should be ignored.

 

§      Contour patterns should be consistent with previous charts.

 

§      When analyzing charts, a rough draft should be done on acetate first. No erasures or sloppiness on final drafts is tolerated. After you are satisfied with your acetate analysis, then you can transfer to final copy using a light table.