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STANDARD DEPICTION OF OBSERVATION REPORTS
Synoptic Surface Plotting Models

Aerographers Mate, Module 01-Surface Weather Observations
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transferred to the chart, and the single plotted chart is used for many different applications. This is done because manually plotting separate charts is very time- consuming.  But  when  observation  data  is  computer plotted, such as done by the TESS system, only data actually needed for a single type of analysis is routinely displayed.  Separate  charts  may  be  produced  very quickly for each individual analysis, especially since the  computer  performs  the  initial  analysis.  For  instance, sea-level pressure, wind speed and direction may be the only parameters plotted for a simple pressure analysis. Only the pressure tendency and change group need be plotted  for  an  isallobaric  analysis. The operator specifies which data to display on the video screen and how the data is to be displayed. The standard plotting models presented in this section should be used as a guide so that the forecaster, when reviewing a "plotted" chart recalled from a saved data file, or a hard-copy of the chart, will be able to interpret the  information.  These  models  are  also  useful  in interpreting  plotted  data  received  via  facsimile  on  either NWS  charts  in  the  United  States  or  from  foreign meteorological  services. Wind Plots Many   prognostic   charts   show   plotted   wind directions and speeds. Winds are always plotted with a system of winds shafts and barbs. The direction is Figure 4-16.—Wind direction in true degrees indicated by the orientation  of  the  wind  shaft  from  the  station  circle  or station location. indicated  by  the  orientation  of  the  shaft  extending  from the  station  circle  (fig.  4-16).  The  wind  speed  is indicated by the barbs on the shaft and gusts are written at the end of the wind shaft (fig. 4-17). TESS 3.0 only . . . A square is used to indicate each 100  knot  increment Flagged  barb  indicates  50  knot  increments  of  wind Single  barb  indicates  10  knot  increments Half  barb  indicates  5  knots No barbs on shaft indicates less than 3 knots An X on the end of the shaft indicates a missing wind speed An X on the center of the shaft indicates a missing wind  direction A  circle  drawn  around  the  station  circle  indicates calm  winds Wind barbs extending clockwise from the wind shaft, as shown above, are used for plots in the Northern Hemisphere.  To  plot  winds  in  the  Southern  Hemisphere,  plot  wind  barbs  so  that  they  extend  counterclockwise from the wind shaft. Figure 4-17.—Wind speed indicated by barbs. Plotted winds are rounded-off to the nearest 5 knots. 4-19





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