GFS forcing: forecast at analysis time

General scientific issues regarding ROMS

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stef
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GFS forcing: forecast at analysis time

#1 Unread post by stef »

Last week I asked a question to ncep.webmaster@noaa.gov about the GFS forcing, but haven't received an answer yet. I was wondering if someone on this forum could help, it might be of interest to many beginners here.

I do not understand the difference between the analysis fields and forecast data with identical valid time, i.e. the forecast at analysis time (step 000hours) e.g.

https://nomads.ncep.noaa.gov/dods/gfs_0 ... 25_00z_anl

and

https://nomads.ncep.noaa.gov/dods/gfs_0 ... s_0p25_00z

at step 000 hours

I compared the prmslmsl fields, and they differ.

I read the following documents:

https://rda.ucar.edu/datasets/ds083.3/docs/FNLvGFS.pdf
https://rda.ucar.edu/datasets/ds083.3/docs/Analysis.pdf

and I think I understand them, but they do not explain the difference (or do they??).

Why does the prmslmsl of the analysis differ from the forecast for analysis time?

Thanks a lot for your help!

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