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<p class="MsoNormal"><span style="font-size:11.0pt;color:black">Hi, Everyone – <o:p>
</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:black">I’m sure many of you are aware of the changes to the GFS that went operational with yesterday’s 12Z run. In the new data files, there are two records for accumulated precipitation that look identical
except for the beginning-of-accumulation information. Here is what the wgrib2 output looks like for the APCP variable in the 12hr forecast and 15hr forecast files:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Andale Mono";color:black"># wgrib2 gfs.t12z.pgrb2.0p25.f012 | grep APCP</span><span style="font-size:10.0pt;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Andale Mono";color:black">449:248062227:d=2019061212:APCP:surface:6-12 hour acc fcst:</span><span style="font-size:10.0pt;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Andale Mono";color:black">450:248429916:d=2019061212:APCP:surface:0-12 hour acc fcst:</span><span style="font-size:10.0pt;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Andale Mono";color:black"> </span><span style="font-size:10.0pt;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Andale Mono";color:black"># wgrib2 gfs.t12z.pgrb2.0p25.f015 | grep APCP</span><span style="font-size:10.0pt;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Andale Mono";color:black">449:246395924:d=2019061212:APCP:surface:12-15 hour acc fcst:</span><span style="font-size:10.0pt;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Andale Mono";color:black">450:246700803:d=2019061212:APCP:surface:0-15 hour acc fcst:</span><span style="font-size:10.0pt;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">The variable in record #449 is the ‘old’ version, with different accumulation periods depending on the forecast hour. The variable in record 450 has the ‘new’ version, with accumulations from the beginning
of the forecast. There is no way to distinguish between these two based on the grib2 codes in a descriptor file. Here’s what I use:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Andale Mono"">p 0,1,0 0,1,8,1 Total Accumulated Precipitation [kg/m2]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">As gribmap examines the records in the grib file to look for matches in the descriptor file, it will find record 449 and index that position for the variable p. Then it will find record 450 and overwrite the
index for the variable p with the new position. So, as long as the ‘new’ version of APCP appears after the ‘old’ version in the grib file, gribmap will index the ‘new’ records, and you can work with the precip data assuming the new accumulation standards.
NCEP says that the ‘old’ variables will be phased out in the near future, so there’s no point in trying to match with the old style records.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">In many ways, the new standard is easier to deal with, although those of us who have written a boatload of scripts to work around the awkwardness of the old standard have some revisions to do. I am working
on modifications to the scripts behind the maps at wxmaps.org and wx.gmu.edu. I hope to have things looking right by the end of the week.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Jennifer<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt">-- <span style="color:black"><br>
Jennifer Miletta Adams<br>
ADNET Systems, Inc.<br>
NASA/GSFC, Code 610.2</span><o:p></o:p></span></p>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;color:black">Building 32, Room S159<br>
(301) 614-6070<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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