The Stage IV analysis is based on the multi-sensor hourly/6-hourly 'Stage III' analyses (on local 4km polar-stereographic grids) produced by the 12 River Forecast Centers (RFCs) in CONUS. NCEP mosaics the Stage III into a national product (the Stage IV). Hourly, 6-hourly and 24-hourly (accumulated from the 6-hourly) analyses are available. The Stage IV differs from the NCEP Stage II chiefly in that the NCEP Stage II contains no manual quality control (QC), while the Stage IV benefits from manual QC performed on the Stage III data at the RFCs.
These data are processed manually monthly, so the date new data are available varies. The data for each month are received from NCEP/EMC around the second week of the following month, and generally loaded within a few days of receipt. If data have not been received by the 20th of the month, then NCEP/EMC is contacted for an update. Since this is a manual process, dates are effected by the availability of the people involved. If data are not available by the 22nd, please feel free to contact codiac for an update.