341 lines
17 KiB
HTML
341 lines
17 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="CONTENT-TYPE" content="text/html; charset=utf-8">
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<title>ShowISC Tools</title>
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<meta name="GENERATOR" content="OpenOffice.org 1.1.2 (Linux)">
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<meta name="AUTHOR" content="tbarker">
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<meta name="CREATED" content="20041012;13500000">
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<meta name="CHANGED" content="20041117;20052300">
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<style>
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@page { size: 8.5in 11in; margin-right: 0.5in; margin-top: 0.83in; margin-bottom: 0.83in }
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P { margin-bottom: 0.08in; direction: ltr; color: #000000; widows: 2; orphans: 2 }
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P.western { font-family: "Times New Roman", serif; font-size: 12pt; so-language: en-US }
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P.cjk { font-family: "Times New Roman", serif; font-size: 12pt }
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P.ctl { font-family: "Times New Roman", serif; font-size: 10pt; so-language: ar-SA }
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-->
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</style>
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<meta content="Tim Barker" name="author">
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</head>
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<body style="color: rgb(0, 0, 0);" dir="ltr" lang="en-US">
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<b><font size="5"><font face="Arial, sans-serif">ShowISC Tools<br>
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</font></font></b></p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<font face="Arial, sans-serif">A collection of tools to mitigate
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site-to-site discrepancies </font>
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</p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<font face="Arial, sans-serif">using algorithms similar to NDFD</font></p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<br>
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</p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<font face="Arial, sans-serif">Tim Barker - WFO Boise, ID</font></p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<br>
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</p>
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<div style="text-align: left;">
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<h2>Table of Contents</h2>
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</div>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center"><br>
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</p>
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<div style="text-align: left;"><a href="#Introduction">Introduction</a><br>
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<a href="#Show_ISC_Highlights">Show_ISC_Highlights</a><br>
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<a href="#Show_ISC_Info">Show_ISC_Info</a><br>
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<a href="ShowISC.html#Show_ISC_Area">Show_ISC_Area</a><br>
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<a href="#Show_ISC_Grid">Show_ISC_Grid</a><br>
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<a href="#Differences">Differences From NDFD Algorithm</a><br>
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<a href="#Install">Configuration</a><br>
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<br>
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</div>
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<div style="text-align: left;">
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<hr style="width: 100%; height: 2px;"><br>
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</div>
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<h2><font face="Arial, sans-serif"><a name="Introduction"></a>Introduction</font></h2>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"><font
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face="Arial, sans-serif">These tools are adaptations upon Tim Barker's
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set of ShowISC tools. These tools were baselined in IFPS16.2
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(November 2004). There are four tools: <br>
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</font></p>
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<ul>
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<li><font face="Arial, sans-serif">Show_ISC_Highlights, which
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highlight grids in the Grid Manager that exceed thresholds on the ISC
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borders,</font></li>
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<li><font face="Arial, sans-serif">Show_ISC_Info, which displays the
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statistics on each border of the CWA,</font></li>
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<li><font face="Arial, sans-serif">Show_ISC_Area, which highlights
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the set of grid points within your CWA that exceed the threshold, and<br>
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</font></li>
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<li><font face="Arial, sans-serif">Show_ISC_Grid, which creates a
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difference grid showing the differences found.<br>
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</font></li>
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</ul>
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<br>
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<hr style="width: 100%; height: 2px;">
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"><br>
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</p>
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<h2><font face="Arial, sans-serif"><b><a name="Show_ISC_Highlights"></a>Show_ISC_Highlights
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</b></font></h2>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"><font
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face="Arial, sans-serif">The tool calculates "discrepant" in the same
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way as
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NDFD (see below for a description of the differences between the NDFD
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algorithm and this algorithm). Essentially, the gridblock will turn
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"red" if the error over <b>any </b>neighboring border would
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violate the NDFD threshold, unless the border is a "short" border
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(as defined in the configuration section - see below), in which
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case it would turn the gridblock "orange". For example, if you
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have five ISC neighbors and the average discrepancy along the border
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with four of them is within the threshold, but the average
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discrepancy for one of the borders violates the threshold - then
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the gridblock will turn red. If it fails for only "short"
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borders - it turns the gridblock red. When you run the tool on a
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vector grid, it checks to see if there is a violation in <b>either</b>
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the magnitude or the direction. </font>
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</p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"><font
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face="Arial, sans-serif">Here
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is a picture of the grid manager after running the
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Show_ISC_Highlights tool on several grids:</font></p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<img alt="" src="images/ShowISCa.png" name="Graphic1"></p>
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<br>
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<font face="Arial, sans-serif">Some
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gridblocks had partial failures and are orange, others had total
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failure are are red. A message is also sent to the GFE status bar,
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either stating that the grid "passed", or had "partial"
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failure or completly "failed" the discrepancy check (green
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messages for "passed" and "yellow" messages for partial and
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failed).</font>
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<hr style="width: 100%; height: 2px;">
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<h2><font face="Arial, sans-serif"><b><a name="Show_ISC_Info"></a>Show_ISC_Info
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</b></font></h2>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"><font
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face="Arial, sans-serif">This tool creates a table of discrepancy
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information for
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each neighboring border. If Show_ISC_Highlights flags a grid as
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"discrepant", this tool can be very helpful for identifying which
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border (or borders) violate the threshold, and by how much.</font></p>
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<br>
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<font face="Arial, sans-serif">For
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example, here is the window created by Show_ISC_Info for a particular
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MinT grid.</font>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center"><img alt="" src="images/ShowISCb.png" name="Graphic2"></p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center"><img alt="" src="images/ShowISCc.png" name="Graphic2"></p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"><font
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face="Arial, sans-serif">For
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each neighbor, it displays the average discrepancy magnitude, the
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threshold for that border, the number of points in the average, and a
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colored message of OK, FAILED or IGNORED. An average of the total
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points along <b>all </b>the borders is also shown at the bottom. The
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IGNORED message is used for borders where the discrepancy is larger
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than the threshold, but the number of points along that border is so
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low that the average is suspicious. This is one of the differences
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from the NDFD algorithm, and is detailed below. By default, a border
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must have 10 gridpoint pairs with a neighbor to be considered - but
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this can be configured (see the <a href="#Install">configuration
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section</a> below).</font></p>
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<br>
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<font face="Arial, sans-serif">For vector parameters like Wind, the
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window will show you the statistics for <b>both</b> magnitude and
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direction, like shown in this example:</font>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center"><img alt="" src="images/ShowISCh.png" name="Graphic3"></p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"><br>
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</p>
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<font face="Arial, sans-serif">You
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can also configure the tool to check thresholds for several
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parameters when you run the tool on certain grids. For example, the
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default configuration is set up so that if you run the tool on an RH
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grid, it will show you statistics for Temperature, Dewpoint, <b>and</b>
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RH, since all three of these parameters are intimately related.</font>
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<hr style="width: 100%; height: 2px;">
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<h2><a name="Show_ISC_Area"></a><font face="Arial, sans-serif"><b>Show_ISC_Area</b></font></h2>
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<font face="Arial, sans-serif">The tool sets the
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edit area to the points <b>inside</b> your forecast area. This tool
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is useful to simply highlight the particular gridboxes where you have
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significant differences with your neighbors. Conceivably, you could
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perform edit operations on these gridboxes to remove the
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discrepancies. However, in practice, this is difficult to do because
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different changes need to be made in different areas.</font>
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<br>
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<font face="Arial, sans-serif"><br>
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In
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this example, the threshold in this area is 7 degrees, and gridboxes
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have been added to the edit area when their difference exceeds 7
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degrees. The forecast CWA is to the "left" in this example, with
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the neighbors' ISC grid shown to the "right"</font>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center"><img alt="" src="images/ShowISCd.png" name="Graphic4"></p>
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<br>
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<font face="Arial, sans-serif">For
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scalar grids like temperature, a gridbox is added to the edit area if
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the maximum difference with any of its neighbors is above the
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threshold. Normally, there is just a single neighboring point, so the
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gridbox is added if the difference is above the threshold. However,
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where there are "corners" in the edit areas, a gridbox inside
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your forecast area might have two (or more) neighboring gridboxes
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inside your neighbors area (for example, one north of your gridbox
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and one west of your gridbox). In these cases, the tool finds the
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maximum difference for any of the neighboring gridboxes, and adds the
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gridbox to the edit area if that difference is greater than the
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threshold. </font>
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<br>
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<font face="Arial, sans-serif"><br>
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An
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example of a corner point is shown in the image below. The point
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labelled 82 is inside the forecast area, and only has a 6 degree
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difference with the point to the north (the threshold is 7 degrees in
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this area). However, this point has a 7 degree difference with the
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point to the west - so the tool added this point to the current
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edit area.</font>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"><br>
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</p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<img alt="" src="images/ShowISCe.png" name="Graphic5"></p>
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<br>
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<font face="Arial, sans-serif">For
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vector grids like Wind, the tool will add a gridbox to the edit area
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if it violates <b>either</b> the magnitude threshold or the direction
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threshold. </font><br>
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<font face="Arial, sans-serif"><br>
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Keep
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in mind that you may have many gridpoints that exceed the threshold
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along a border with your neighbor, but the <b>average </b>discrepancy
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along the border is what is used to determine if that border is
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"discrepant" or not. Thus, even though a border is not flagged
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as "discrepant" by the other tools, you may still have many
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points in the edit area created by Show_ISC_Area.</font>
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<span style="font-family: "times new roman",serif;"><br>
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</span>
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<hr style="width: 100%; height: 2px;">
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<h2><a name="Show_ISC_Grid"></a><span
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style="font-family: "times new roman",serif;"></span><font
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face="Arial, sans-serif"><b>Show_ISC_Grid</b></font></h2>
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<font face="Arial, sans-serif">The tool
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sets the gridpoint <b>inside</b> your border equal to the maximum
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difference
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between that gridpoint and your neighbors gridpoints. The
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Show_ISC_Area tool discussed above basically shows you <b>where</b>
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you have differences above the threshold, while the grid calculated
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by Show_ISC_Grid shows you<b> how big</b> the differences are.</font>
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<br>
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<font face="Arial, sans-serif"><br>
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Here
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are example difference grids for the two areas shown above for the
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Show_ISC_Area tool:</font>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center"><img alt="" src="images/ShowISCf.png" name="Graphic6"></p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<br>
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</p>
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<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"
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align="center">
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<img alt="" src="images/ShowISCg.png" name="Graphic7"></p>
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<p class="western"
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style="margin-left: 0.25in; margin-bottom: 0in; widows: 0; orphans: 0;">
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<br>
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</p>
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<font face="Arial, sans-serif">Note
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that the differences are plotted for every point along the border,
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not just the points that are larger than the coodination threshold.
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Also note that the differences are positive when the gridpoint is
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higher than the neighboring point, and the difference is negative
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when the gridpoint is lower than the neighboring point.</font>
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<hr style="width: 100%; height: 2px;">
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<h2><a name="Differences"></a><font face="Arial, sans-serif"><font
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size="5"><b>Differences
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with NDFD algorithm</b></font></font></h2>
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<font face="Arial, sans-serif">As
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of September 2004, the differences from the NDFD algorithm are:</font>
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<p class="western"
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style="margin-left: 0.25in; margin-bottom: 0in; widows: 0; orphans: 0;"><font
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face="Arial, sans-serif">In order to come up with the exact
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same statistics the NDFD and GFE must agree EXACTLY on the location
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of the border between two CWAs. Both NDFD and GFE determine if a
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gridbox belongs to one CWA or another based on whether the center of
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the gridbox lies on which "side" of the CWA border. To make
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drawing operations more efficient, GFE 'thins' the points along
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the shapefile borders by 'combining' points that are within a
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certain 'precision' in terms of latitude and longitude. By
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default, GFE sets this to 2 decimal places. For example, if two
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points along the border have the same latitude, but have longitudes
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of 105.243 and 105.238, they would be 'combined' into a single
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point. While this makes almost no difference visually on the GFE
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displays, it CAN have an impact when determining if the center of a
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gridbox lies on which "side" of a shapefile border. <!-- A little
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known configuration element in the IFPServer allows you to control
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the precision of the shapefile points. This is discussed in the
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documentation for the GFE Map files. For each map, you can specify a
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precision. It defaults to 2 (for two decimal places), but higher
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numbers will store more decimal places of precision. In addition,
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you can set the precision to None, which will NOT allow the shapefile
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borders to be thinned at all. In my case, I found virtually no
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discernable difference running the server with either 2 or 4 decimal
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places - or even setting the precision to None. --></font></p>
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<p class="western"
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style="margin-left: 0.25in; margin-bottom: 0in; widows: 0; orphans: 0;">
|
||
|
|
<font face="Arial, sans-serif">Using this higher precision, the location of the borders
|
||
|
|
is much closer to what is calculated with NDFD. However, even with
|
||
|
|
this high precision, roundoff errors lead to a few gridboxes placed
|
||
|
|
on different "sides" of the CWA border. If identical results are
|
||
|
|
desired, IFP focal points might need to override the ISC_xxx edit
|
||
|
|
areas to ensure that points are identically assigned as they are at
|
||
|
|
NDFD. Other differences between the NDFD calculations and the
|
||
|
|
calculations in these tools have been corrected - so the impact of
|
||
|
|
this difference is quite small, and for many borders is
|
||
|
|
non-existantant. For sites that run at a different resolution than
|
||
|
|
the 5-km resolution of NDFD, the border points will already be much
|
||
|
|
different - so this small difference is irrelevant.</font></p>
|
||
|
|
|
||
|
|
<p class="western"
|
||
|
|
style="margin-left: 0.25in; margin-bottom: 0in; widows: 0; orphans: 0;">
|
||
|
|
<font face="Arial, sans-serif">The NDFD algorithm will mark a
|
||
|
|
particular border as "failing" (marked with a "frowny face")
|
||
|
|
whenever the average difference is above the threshold. The
|
||
|
|
algorithm used here ignores averages that have less than 10
|
||
|
|
gridboxes. This is to keep discrepancies along very short borders
|
||
|
|
from marking the whole grid as "suspicious". This value is
|
||
|
|
configurable in the Show_ISC_Highlights and Show_ISC_Info tools -
|
||
|
|
as discussed in the installation section below.</font></p>
|
||
|
|
<p class="western" style="margin-bottom: 0in; widows: 0; orphans: 0;"><br>
|
||
|
|
</p>
|
||
|
|
<font face="Arial, sans-serif">In order to ignore light wind
|
||
|
|
difference, in both the wind speed and wind direction calculations,
|
||
|
|
the NDFD algorithm also ignores neighboring gridbox pairs where
|
||
|
|
either wind speed value is below 8 knots. This means that your
|
||
|
|
gridbox can have 0 knots, and your neighboring gridbox can have 50
|
||
|
|
knots or more - and NDFD will not mark it as violating the
|
||
|
|
threshold! In the algorithm used here, neighboring gridbox pairs are
|
||
|
|
ignored only if BOTH points are below 8 knots.<br>
|
||
|
|
</font>
|
||
|
|
<hr style="width: 100%; height: 2px;">
|
||
|
|
<h2><a name="Install"></a><font face="Arial, sans-serif"><font size="5"><b>Configuration</b></font></font></h2>
|
||
|
|
The ShowISC tools on the Smart Tool Repository required configuration
|
||
|
|
for each site. The baselined version are automatically configured
|
||
|
|
based on edit area information within EDEX.<br>
|
||
|
|
<br>
|
||
|
|
The Show_ISC_Info and Show_ISC_Highlights tools have a common
|
||
|
|
configuration section within the ISC_Utility. You can override
|
||
|
|
these values by copying the configuration() function from ISC_Utility
|
||
|
|
and putting it into ISC_Utility_Local, and then changing the values.<br>
|
||
|
|
<span style="font-family: courier,monospace;"></span><br>
|
||
|
|
<br>
|
||
|
|
</body>
|
||
|
|
</html>
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