322 lines
14 KiB
HTML
322 lines
14 KiB
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<title>TCMWindTool</title>
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<body dir="ltr" lang="de-DE" text="#000000">
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<p class="western" style="margin-bottom: 0in;" align="center"
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lang="en-US">
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<font size="6"><b>TCMWind Tool</b></font></p>
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<h1>
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<font size="4"><b>March 9, 2012</b></font></h1>
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<p class="western" style="margin-bottom: 0in;" align="center"
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lang="en-US">
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<br>
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</p>
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<font size="3">The TCMWind tool was designed to read and decode the TCM
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text bulletin and create a sequence of wind grids based on the
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location and wind radii information. Forecasters can choose between
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the current forecast, NAM, or the GFS as background wind fields. The
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tool generates wind grids based on the local wind time constraints.
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For example, if a site configures the wind weather element such that
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there is a grid every hour, the tool will produce a wind grid every
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hour for the time span of the the TCM bulletin (usually 5 days).</font>
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<font size="3"></font>
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<h1><font size="5"><b>Running the Tool</b></font></h1>
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<p class="western" style="margin-bottom: 0in;" align="left" lang="en-US">
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</p>
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<font size="3">To run the TCMWind tool, select from the GFE main menu, </font>
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<p class="western" style="margin-bottom: 0in;" align="left" lang="en-US"></p>
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<p class="western" style="margin-bottom: 0in;" align="center"
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lang="en-US">
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</p>
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<h1><font size="3"><b>Populate->TCMWindTool. </b></font></h1>
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<p class="western" style="margin-bottom: 0in;" align="center"
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lang="en-US"></p>
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<p class="western" style="margin-bottom: 0in;" align="left" lang="en-US">
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<br>
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</p>
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<font size="3">As soon as the tool starts, it displays a dialog that
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looks like Figure 1 below. Using this dialog you can indicate the
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TCM bulletin that should be decoded, the background wind field, the
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eye diameter, the 34-knot radius at 3, 4, and 5 days, and whether you
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want the tool to make wind grids over the selected time range only.
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Each of the options are described in more detail below.</font>
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<h1><font size="4"><b>Product to decode</b></font></h1>
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<font size="3">Each new tropical cyclone is assigned a slightly
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different product PIL. It is very important that you select the
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correct product name or the wrong TCM will be decoded and plotted. Use
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one of the first two columns of product PILs to select the
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appropriate product. One and only one selection is allowed. Any
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more or less than one will result in an error message in the form of
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a GFE yellow banner.</font>
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<p class="western" style="margin-bottom: 0in;" align="left" lang="en-US"><br>
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</p>
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<p class="western" style="margin-bottom: 0in;" align="left" lang="en-US">
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<img alt="TCMWind tool user interface" src="images/TCMWindToolUI.png"
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name="Graphic1" align="left"><br>
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</p>
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<br>
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</p>
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<font size="3"><b><br>
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Figure 1 - Snapshot of the TCMWindTool interface</b></font>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><br>
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</p>
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<h1>
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<font size="4"><b>Background Model</b></font></h1>
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<p class="western" style="margin-bottom: 0in;" align="left" lang="en-US">
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<br>
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</p>
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<font size="3">This is where you select the background for your grid.
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The tool will do its best to match the time of the model (or Fcst)
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grid with the time of the cyclone. The background grid is blended
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with the cyclone wind field so that you have winds defined over your
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entire domain.</font>
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<h1><font size="4"><b>Eye Diameter</b></font></h1>
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<p class="western" style="margin-bottom: 0in;" align="left" lang="en-US">
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<br>
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</p>
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<font size="3">TPC will generally report an observed eye diameter in
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the TCM bulletin. This value is used to calculate the radius of
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maximum wind (RMW) using this equation:</font>
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<p class="western" style="margin-bottom: 0in;" align="center"
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lang="en-US"> </p>
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<h3><font size="3"><b>RMW = (EyeDiameter / 2.0) + 8.0</b></font></h3>
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<p class="western" style="margin-bottom: 0in;" align="center"
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lang="en-US"></p>
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<font size="3">The value for this radius of maximum wind is used
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throughout the 5-day forecast period. If you wish to override this
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TPC value, move the slider bar to the right. Any value greater than
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zero will be used by the tool. If you do not adjust this slider, the
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value used will be the same as found in the TCM bulletin.<br>
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<br>
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</font>
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<h1><font size="4"><b>34 knot radius at 3 days (4 days) (5 days)</b></font></h1>
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<font size="3">Beyond 72 hours, the TCM bulletin defines only a center
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location and maximum sustained wind at 24 hour intervals. To better
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define the spatial extent of the cyclone for the 3-5 day period,
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three sliders allow the forecasters to set the radius of the 34 knot
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wind threshold at 24 hour intervals. This is effectively the same as
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if the TCM bulletin defined 34 knot radii at these distances. To
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adjust the radii, simply move the slider to the desired value for
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each of the sliders.<br>
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<br>
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</font>
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<h1><font size="4"><b>Decrease Wind over Land by (%)</b></font></h1>
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Adjusting this slider will reduce the wind magnitude over areas where
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the elevation is greater than zero (above sea level). Note that the
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scale range is from -20% to +50%. Negative values will increase the
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wind magnitude by that amount over areas above sea level.<br>
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<br>
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<br>
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<font size="4"><b>Make Grid over Selected Time Only</b></font><br>
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<br>
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Selecting “Yes” for this option will produce grids only over a
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time range that you select in the grid manager. Selecting “No”
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will cause the tool to create grids for the entire forecast period of
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the TCM bulletin. De-selecting the grid manager time range will have
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the same effect as selecting “No”. If you have a time range
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selected and select “Yes” to “Make Grid Over Selected Time
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Only”, but your selected time does not intersect the valid time of
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the TCM bulletin, a yellow banner will display informing you that you
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selected a time outside the time period defined in the bulletin.<br><br>
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<font size="4"><b>MakeWind Swath for TCWindThreat?</b></font><br>
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<br>
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This option is for use only by those offices that are part of Tropical
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Impact Graphics experiment. This option, using the detailed wind radii info
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provided calculates a swath of maximum wind for each grid point that incorporates
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the specified land friction. This creates a TCMMaxWindComposite object that
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gets stored in the server. When the office runs the TCWindThreat tool as part of the tropical
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impact grids/graphics, that object is available as one of two options for use as the
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deterministic WindMax source. In the context of the TCWindThreat tool, the WindMax
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source created by the TCMWindTools would be named TCM. The downside to running
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TCMWindTool with this option is that it will take 5 to 6 extra minutes to run.</font><br>
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<h1><big><font size="5"><big><b>The Algorithm</b></big></font></big></h1>
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The algorithm used to calculate the wind field is roughly a Rankine
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vortex. Wind values at specified radii are defined in the TCM bulletin.
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Wind values between these radii are interpolated using an exponential
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curve. An example of this curve using forecast data from the northeast
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quadrant of Hurricane Irene (17 Oct 1999) is shown in Figure 2 below.<br>
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<font face="Nimbus Roman No9 L, Times New Roman"><font size="3"><br>
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</font></font><br>
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<p style="margin-bottom: 0in;" align="left" lang="en-US"><img
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alt="Rankine example" src="images/TCMWindToolRankine.png"
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name="Graphic2"
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style="border: 0px solid ; width: 516px; height: 537px;" align="left"><br>
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</p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><font size="3"><b><br>
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</b></font></p>
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<font size="3"><b><br>
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Figure 2 – Example of Rankine vortex algorithm that
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interpolates wind speed as a function of distance fro the center.</b></font><br>
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<br>
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<br>
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This process is repeated for each quadrant, based on the specified
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radii in the TCM bulletin. This technique is used to calculate the
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winds from the RMW outward. A linear curve is used to calculate wind
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values from the RMW toward the center.<br>
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<h1><big><font face="Nimbus Roman No9 L, Times New Roman"><font size="4"><big><b>Wind
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Speed Caps</b></big></font></font></big></h1>
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Based on guidance from the TPC and the wind team, limitations on the
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magnitude of the wind are applied based on the forecast lead-time.
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These wind caps are documented in the table below.<br>
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<br>
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<span style="font-weight: bold;">Wind Caps for TCMWind Tool</span><br>
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<br>
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<table border="1" bordercolor="#000000" cellpadding="4" cellspacing="0"
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width="577">
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<col width="279"> <col width="280"> <thead> <tr valign="top">
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<td width="279"> Forecast period </td>
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<td width="280"> Maximum Allowed Wind Value </td>
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</tr>
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</thead> <tbody>
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<tr valign="top">
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<td width="279"> 0 – 24 hours </td>
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<td width="280"> Maximum Sustained Wind </td>
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</tr>
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<tr valign="top">
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<td width="279"> 25-72 hours </td>
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<td width="280"> 100 knots </td>
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</tr>
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<tr valign="top">
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<td width="279"> 73-120 hours </td>
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<td width="280"> 64 knots </td>
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</tr>
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</tbody>
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</table>
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<p style="margin-bottom: 0in;" align="left" lang="en-US"><br>
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</p>
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<font size="3"><b>Table 1 – List of wind speed caps as a function of
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lead time.</b></font>
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<p class="western" style="margin-left: 1in; margin-bottom: 0in;"
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align="left" lang="en-US"><br>
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</p>
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</body>
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