NCEP/EMC 4KM Gridded Data (GRIB) Stage IV Data
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. As of April 2017 this data includes Alaska and Puerto Rico stations. As of 20 July 2020, data file formats changed from GRIB1 to GRIB2, with similar name changes (e.g., *.grb2). Starting on 20 July 2020, the GRIB1 files may not have complete data. Please refer to the GRIB2 files instead.
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 affected by the availability of EOL staff. If data are not available by the 22nd, please contact us for an update.
System order size limits are about 3 months of data. If you need to download the entire dataset at once immediately, please contact us for alternate download arrangements (subject to EOL staff availability).
January 18, 2019: It was noticed that the Alaska and Puerto Rico stations were not actually included in the dataset as mentioned in the data description. As of this date, all the data (from April 2017) for the Alaska and Puerto Rico stations are now included in this dataset.
January 15, 2020: Data for 26 September 2019 was added when it was determined that this date had been omitted.
March 26, 2020: Data for 01 January 2020 was added when it was determined that this date had been omitted.
31 August 2020: Start and end dates/times on the files were updated.
7 October 2020: As of 20 July 2020, data file formats changed from GRIB1 to GRIB2, with similar name changes (e.g., *.grb2). Starting on 20 July 2020, the GRIB1 files may not have complete data. Please refer to the GRIB2 files instead.
7 October 2020: As of 20 July 2020, file names changed from ST4*.gz to st4_conus*.grb2. Starting on 20 July 2020, if both files exist, please refer to the st4_conus*.grb2 file for the most complete data.
3 February 2021: Files missing from January 2002, April 2008, and January 2012 were added.
January 28 - 30, 2019 - some stage 4 data missing
April 4, 2019 - all data missing
September 26, 2019 - all data missing
November 20, 2019 - some stage 2 and some stage 4 missing
November 21, 2019 - some stage 2 missing
January 1, 2020 - all stage 4 and some stage 2 missing
March 25, 2020 - AK missing for 00, 06, and 12 hours
August 2021 - AK missing from 8/29 18:00 through 8/31 12:00
November 10, 2021 - AK missing most data
- ORDER data for delivery by FTP
|Begin datetime||2001-12-31 12:00:01|
|End datetime||2023-08-31 23:00:00|
Map data from IBCSO, IBCAO, and Global Topography.
Maximum (North) Latitude:
Minimum (South) Latitude:
Minimum (West) Longitude: -176.836, Maximum (East) Longitude: -65.544
Additional contact information
CitationExample citation following ESIP guidelines:
Du, J. 2011. NCEP/EMC 4KM Gridded Data (GRIB) Stage IV Data. Version 1.0. UCAR/NCAR - Earth Observing Laboratory. https://doi.org/10.5065/D6PG1QDD. Accessed 27 Sep 2023.
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