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9.0.15.0 NMAP Product Generation

Graphically Modifying A Grid

Here we will modify the ETA surface pressure grid (EMSL) for the 0 hour forecast (F000) of the most recent run. The grid values will be stored to reflect the graphical changes made.

  1. Create a VGF output file for the desired grid

    2. In this example, we will use GDCNTR with the VG device driver. To make it easier to deal with the grid contours in the product generator, use the LINE parameter setting for labels on every contour line, without breaking the contour line for the label. This is done with a label setting of -1 in LINE. We'll use a contour interval of 2mb for a reasonable level of resolution in the display.

  2. Import the VGF file into NMAP using the product generation tool

    3. Nmap pgen grid import

  3. Select the modification (Mod) action from the product generation palette

    4. Using the modification action, select a contour in the image to be modified using the left mouse button. Now, select a starting point in the contour where modifications will begin. The updated contour line will begin following the mouse pointer. Use the left mouse button to place now vertex points along the updated contour. Click the middle mouse button when the update is complete.

    Nmap pgen grid modify2 Nmap pgen grid modify3

  4. Create new countour levels

    5. Using the Lines class, and contour object, set the attributes for the contour line in the popup menu, then draw your contour. When your contour is complete, the Text Attributes box will pop up. Enter the value for the contour label in the text box and then place the text box in the image using the mouse pointer.

    Nmap pgen grid modify4 Nmap pgen grid modify5

  5. Save your grid to a grid file

    6. Select the PROD class object Graph-to-Grid. Since this is not one of the defined products, set the PRODUCT indicator to NONE. We'll use the Advanced menu to set all the properties for our grid file to be created. As shown below, our output grid will be written to a file called eta.grd that will be created using the Grid #211 definitions. The grid product will be called EMSL and soted on a grid level of 0 and a vertical coordinate of none.

    Nmap pgen grid modify6

  6. Compare the grids

    7. We can view our grids in GDCNTR (or any other grid program, including NMAP). The original grid is shown on the left (cyan contours), and the modified grid is shown on the right (yellow contours). Note the changes made to the low pressure center over Wyoming, and the associated trough. The updated grid can be used in any GEMPAK grid diagnostics to examine how the changes made to the analyzed storm can effect other quantities.

    Nmap pgen grid modify7

9.0.15.0.0  NMAP Product Generation Exercise (GDCNTR)

 


Previous: NMAP Examples Next: NMAP Product Generation Exercise (GDCNTR) Table of contents Frames User Manual GEMPAK Online Tutorial > NPROGS > NMAP2 > NMAP Examples

 
 
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