Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) Forum

RR1h grib source?

Posted By: Peter Buckner
Date: 28-September-12 1747Z

Great resource! Thanks for keeping this active. On looking at details for a particular RR1h sounding, I find two question, as I compare the GSD formatted Ascii output provided by this rucsoundings.noaa.gov webpage and the current grib2 file obtained from www.ftp.ncep.noaa.gov/.../rap.t15z.awp130bgrbf00.grib2. These question lead me to wonder, from which grib is this web page pulling it's data for RR1h? First question is: 1) Why don't the grid point align? For example, webpage query for airport MEI indicates nearest grid point is 32.36, -88.68. Looking into grib file itself, the nearest grid point is 32.35, -88.71. Not a huge difference, but there should be zero difference, if source gribs match. Further checks using lower resolution grib files also do not contain grid point 32.36, -88.68. (I've also tried awp252, awp236, awip32) Is the web page using a different grib, or is it interpolating the same grib, but to a different grid? $ wgrib2 -v -lon 271.32 32.36 yields: ...lon=271.292332,lat=32.349135 2)... and this is clearly related to #1. Data values don't match. Comparing temperatures at the same level result in differences in multiple degrees, sometimes higher, sometimes lower. I'd expect small differences given the different latitude/longitudes of the grid points, but these difference look to be larger than one might explain. I'm careful to use only the 00 hour forecast grin files with an identical time to the webpage sounding. For example, if the GSD formatted Ascii indicates "RR1h 15 28 Sep 2012", I'm using grib rap/20120928/rap.t15z.awp130bgrbf00.grib2. Am I using the wrong grin file?

Messages In This Thread

RR1h grib source? -- Peter Buckner -- 28-September-12 1747Z

Re: RR1h grib source? -- Peter Buckner -- 9-October-12 1532Z

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