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problem in access to RUC analyses on NCEP ftp server

Posted By: Stan Benjamin
Date: 5-February-04 1106Z

If you ftp RUC data from the NCEP ftp server at ftpprd.ncep.noaa.gov, keep reading.

Basically, the problem is that unless you've taken special precautions in your ftp scripts, you've been accessing RUC analyses at 0000 and 1200 UTC that do not assimilate most of the raob data.

Let me explain: There are 2 RUC analyses in the operational NCEP version at 00z and 12z only. The first is an "early look" analysis, called the "A" analysis that misses most of the raob data (although it does have most of the other obs in it - profiler, aircraft, sfc, etc.). The 00z and 12z RUC forecasts do NOT run off the "A" analysis. Instead, a second analysis called the "B" analysis with a later (30 min) data cut-off to catch raob data is run, and then the forecast is run.

At the NCEP ftp site, the ruc2a directories contain the "A" analyses and forecasts initialized from the "B" analysis. Yes, a little confusing. To obtain the "B" analyses, you must go to the corresponding ruc2b directory. In other words, you must access two different directories to obtain the best RUC analysis and forecast (from the B run) at 0000 and 1200 UTC. Again, there is no B run at times other than 0000 and 1200 UTC.

The information on the RUC web site about ftp'ing from the NCEP-ftp site was NOT correct about this issue until this afternoon. It is now corrected (see http://ruc.fsl.noaa.gov/ruc20.data-access.html). I apologize for this error.

It is likely that we will try to get rid of the early look "A" analysis entirely to avoid any more of this confusion. Geoff Manikin and I posted this idea back on 23 April 02 and received no email from anyone who opposed this idea. If you want to keep the "A" analysis, speak now.

My apologies to anyone who has been misled by this problem, and I know there are at least a few of you.

Stan

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problem in access to RUC analyses on NCEP ftp server -- Stan Benjamin -- 5-February-04 1106Z

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